[PATCH v2 0/7] Move pKVM ownership state to hyp_vmemmap

[PATCH v2 0/7] Move pKVM ownership state to hyp_vmemmap

[Quentin Perret]

Hi all,

This series moves the hypervisor's ownership state to the hyp_vmemmap,
as discussed in [1]. The two main benefits are:

 1. much cheaper hyp state lookups, since we can avoid the hyp stage-1
    page-table walk;

 2. de-correlates the hyp state from the presence of a mapping in the
    linear map range of the hypervisor; which enables a bunch of
    clean-ups in the existing code and will simplify the introduction of
    other features in the future (hyp tracing, ...)

Patch 01 is a self-sufficient cleanup that I found thanks to patch 06.
Patch 02 is another self-sufficient cleanup that came out from the
discussion with Marc at [2]. Patches 03-05 implement the aforementioned
migration of the hyp state to the vmemmap. Patches 06 and 07 are further
improvements enabled by that migration.

Changes since v1:
 - fixed page-tracking comments in nvhe/memory.h
 - rebased on 6.15-rc2
 - applied Marc's Reviewed-by

Thanks,
Quentin

[1] https://lore.kernel.org/kvmarm/Z79ZJVOHtNu6YsVt@google.com/
[2] https://lore.kernel.org/kvmarm/867c4pnspi.wl-maz@kernel.org/

Fuad Tabba (1):
  KVM: arm64: Track SVE state in the hypervisor vcpu structure

Quentin Perret (6):
  KVM: arm64: Fix pKVM page-tracking comments
  KVM: arm64: Use 0b11 for encoding PKVM_NOPAGE
  KVM: arm64: Introduce {get,set}_host_state() helpers
  KVM: arm64: Move hyp state to hyp_vmemmap
  KVM: arm64: Defer EL2 stage-1 mapping on share
  KVM: arm64: Unconditionally cross check hyp state

 arch/arm64/include/asm/kvm_host.h        |  12 +--
 arch/arm64/kvm/hyp/include/nvhe/memory.h |  58 ++++++++++---
 arch/arm64/kvm/hyp/nvhe/hyp-main.c       |   4 -
 arch/arm64/kvm/hyp/nvhe/mem_protect.c    | 106 ++++++++++++-----------
 arch/arm64/kvm/hyp/nvhe/pkvm.c           |  47 +++++++++-
 arch/arm64/kvm/hyp/nvhe/setup.c          |  10 ++-
 6 files changed, 158 insertions(+), 79 deletions(-)

-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 1/7] KVM: arm64: Track SVE state in the hypervisor vcpu structure

[Quentin Perret]

From: Fuad Tabba <tabba@google.com>

When dealing with a guest with SVE enabled, make sure the host SVE
state is pinned at EL2 S1, and that the hypervisor vCPU state is
correctly initialised (and then unpinned on teardown).

Co-authored-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/include/asm/kvm_host.h  | 12 ++++----
 arch/arm64/kvm/hyp/nvhe/hyp-main.c |  4 ---
 arch/arm64/kvm/hyp/nvhe/pkvm.c     | 47 ++++++++++++++++++++++++++++--
 3 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e98cfe7855a6..931011b68819 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -971,20 +971,22 @@ struct kvm_vcpu_arch {
 #define vcpu_sve_zcr_elx(vcpu)						\
 	(unlikely(is_hyp_ctxt(vcpu)) ? ZCR_EL2 : ZCR_EL1)
 
-#define vcpu_sve_state_size(vcpu) ({					\
+#define sve_state_size_from_vl(sve_max_vl) ({				\
 	size_t __size_ret;						\
-	unsigned int __vcpu_vq;						\
+	unsigned int __vq;						\
 									\
-	if (WARN_ON(!sve_vl_valid((vcpu)->arch.sve_max_vl))) {		\
+	if (WARN_ON(!sve_vl_valid(sve_max_vl))) {			\
 		__size_ret = 0;						\
 	} else {							\
-		__vcpu_vq = vcpu_sve_max_vq(vcpu);			\
-		__size_ret = SVE_SIG_REGS_SIZE(__vcpu_vq);		\
+		__vq = sve_vq_from_vl(sve_max_vl);			\
+		__size_ret = SVE_SIG_REGS_SIZE(__vq);			\
 	}								\
 									\
 	__size_ret;							\
 })
 
+#define vcpu_sve_state_size(vcpu) sve_state_size_from_vl((vcpu)->arch.sve_max_vl)
+
 #define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \
 				 KVM_GUESTDBG_USE_SW_BP | \
 				 KVM_GUESTDBG_USE_HW | \
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 2c37680d954c..59db9606e6e1 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -123,10 +123,6 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
 
 	hyp_vcpu->vcpu.arch.ctxt	= host_vcpu->arch.ctxt;
 
-	hyp_vcpu->vcpu.arch.sve_state	= kern_hyp_va(host_vcpu->arch.sve_state);
-	/* Limit guest vector length to the maximum supported by the host.  */
-	hyp_vcpu->vcpu.arch.sve_max_vl	= min(host_vcpu->arch.sve_max_vl, kvm_host_sve_max_vl);
-
 	hyp_vcpu->vcpu.arch.mdcr_el2	= host_vcpu->arch.mdcr_el2;
 	hyp_vcpu->vcpu.arch.hcr_el2 &= ~(HCR_TWI | HCR_TWE);
 	hyp_vcpu->vcpu.arch.hcr_el2 |= READ_ONCE(host_vcpu->arch.hcr_el2) &
diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 5a335a51deca..338505cb0171 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -372,6 +372,18 @@ static void unpin_host_vcpu(struct kvm_vcpu *host_vcpu)
 		hyp_unpin_shared_mem(host_vcpu, host_vcpu + 1);
 }
 
+static void unpin_host_sve_state(struct pkvm_hyp_vcpu *hyp_vcpu)
+{
+	void *sve_state;
+
+	if (!vcpu_has_feature(&hyp_vcpu->vcpu, KVM_ARM_VCPU_SVE))
+		return;
+
+	sve_state = kern_hyp_va(hyp_vcpu->vcpu.arch.sve_state);
+	hyp_unpin_shared_mem(sve_state,
+			     sve_state + vcpu_sve_state_size(&hyp_vcpu->vcpu));
+}
+
 static void unpin_host_vcpus(struct pkvm_hyp_vcpu *hyp_vcpus[],
 			     unsigned int nr_vcpus)
 {
@@ -384,6 +396,7 @@ static void unpin_host_vcpus(struct pkvm_hyp_vcpu *hyp_vcpus[],
 			continue;
 
 		unpin_host_vcpu(hyp_vcpu->host_vcpu);
+		unpin_host_sve_state(hyp_vcpu);
 	}
 }
 
@@ -398,12 +411,40 @@ static void init_pkvm_hyp_vm(struct kvm *host_kvm, struct pkvm_hyp_vm *hyp_vm,
 	pkvm_init_features_from_host(hyp_vm, host_kvm);
 }
 
-static void pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
+static int pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
 {
 	struct kvm_vcpu *vcpu = &hyp_vcpu->vcpu;
+	unsigned int sve_max_vl;
+	size_t sve_state_size;
+	void *sve_state;
+	int ret = 0;
 
-	if (!vcpu_has_feature(vcpu, KVM_ARM_VCPU_SVE))
+	if (!vcpu_has_feature(vcpu, KVM_ARM_VCPU_SVE)) {
 		vcpu_clear_flag(vcpu, VCPU_SVE_FINALIZED);
+		return 0;
+	}
+
+	/* Limit guest vector length to the maximum supported by the host. */
+	sve_max_vl = min(READ_ONCE(host_vcpu->arch.sve_max_vl), kvm_host_sve_max_vl);
+	sve_state_size = sve_state_size_from_vl(sve_max_vl);
+	sve_state = kern_hyp_va(READ_ONCE(host_vcpu->arch.sve_state));
+
+	if (!sve_state || !sve_state_size) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	ret = hyp_pin_shared_mem(sve_state, sve_state + sve_state_size);
+	if (ret)
+		goto err;
+
+	vcpu->arch.sve_state = sve_state;
+	vcpu->arch.sve_max_vl = sve_max_vl;
+
+	return 0;
+err:
+	clear_bit(KVM_ARM_VCPU_SVE, vcpu->kvm->arch.vcpu_features);
+	return ret;
 }
 
 static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
@@ -432,7 +473,7 @@ static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
 	if (ret)
 		goto done;
 
-	pkvm_vcpu_init_sve(hyp_vcpu, host_vcpu);
+	ret = pkvm_vcpu_init_sve(hyp_vcpu, host_vcpu);
 done:
 	if (ret)
 		unpin_host_vcpu(host_vcpu);
-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 2/7] KVM: arm64: Fix pKVM page-tracking comments

[Quentin Perret]

Most of the comments relating to pKVM page-tracking in nvhe/memory.h are
now either slightly outdated or outright wrong. Fix the comments.

Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/memory.h | 29 ++++++++++++++++--------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
index 34233d586060..178028172c0b 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
@@ -8,20 +8,29 @@
 #include <linux/types.h>
 
 /*
- * Bits 0-1 are reserved to track the memory ownership state of each page:
- *   00: The page is owned exclusively by the page-table owner.
- *   01: The page is owned by the page-table owner, but is shared
- *       with another entity.
- *   10: The page is shared with, but not owned by the page-table owner.
- *   11: Reserved for future use (lending).
+ * Bits 0-1 are used to encode the memory ownership state of each page from the
+ * point of view of a pKVM "component" (host, hyp, guest, ... see enum
+ * pkvm_component_id):
+ *   00: The page is owned and exclusively accessible by the component;
+ *   01: The page is owned and accessible by the component, but is also
+ *       accessible by another component;
+ *   10: The page is accessible but not owned by the component;
+ * The storage of this state depends on the component: either in the
+ * hyp_vmemmap for the host state or in PTE software bits for the hypervisor
+ * and guests.
  */
 enum pkvm_page_state {
 	PKVM_PAGE_OWNED			= 0ULL,
 	PKVM_PAGE_SHARED_OWNED		= BIT(0),
 	PKVM_PAGE_SHARED_BORROWED	= BIT(1),
-	__PKVM_PAGE_RESERVED		= BIT(0) | BIT(1),
-
-	/* Meta-states which aren't encoded directly in the PTE's SW bits */
+	__PKVM_PAGE_RESERVED            = BIT(0) | BIT(1),
+
+	/*
+	 * 'Meta-states' are not stored directly in PTE SW bits for hyp and
+	 * guest states, but inferred from the context (e.g. invalid PTE
+	 * entries). For the host, meta-states are stored directly in the
+	 * struct hyp_page.
+	 */
 	PKVM_NOPAGE			= BIT(2),
 };
 #define PKVM_PAGE_META_STATES_MASK	(~__PKVM_PAGE_RESERVED)
@@ -44,7 +53,7 @@ struct hyp_page {
 	u16 refcount;
 	u8 order;
 
-	/* Host (non-meta) state. Guarded by the host stage-2 lock. */
+	/* Host state. Guarded by the host stage-2 lock. */
 	enum pkvm_page_state host_state : 8;
 
 	u32 host_share_guest_count;
-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 3/7] KVM: arm64: Use 0b11 for encoding PKVM_NOPAGE

[Quentin Perret]

The page ownership state encoded as 0b11 is currently considered
reserved for future use, and PKVM_NOPAGE uses bit 2. In order to
simplify the relocation of the hyp ownership state into the
vmemmap in later patches, let's use the 'reserved' encoding for
the PKVM_NOPAGE state. The struct hyp_page layout isn't guaranteed
stable at all, so there is no real reason to have 'reserved' encodings.

No functional changes intended.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/memory.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
index 178028172c0b..bf28f9f9de65 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
@@ -23,7 +23,6 @@ enum pkvm_page_state {
 	PKVM_PAGE_OWNED			= 0ULL,
 	PKVM_PAGE_SHARED_OWNED		= BIT(0),
 	PKVM_PAGE_SHARED_BORROWED	= BIT(1),
-	__PKVM_PAGE_RESERVED            = BIT(0) | BIT(1),
 
 	/*
 	 * 'Meta-states' are not stored directly in PTE SW bits for hyp and
@@ -31,9 +30,8 @@ enum pkvm_page_state {
 	 * entries). For the host, meta-states are stored directly in the
 	 * struct hyp_page.
 	 */
-	PKVM_NOPAGE			= BIT(2),
+	PKVM_NOPAGE			= BIT(0) | BIT(1),
 };
-#define PKVM_PAGE_META_STATES_MASK	(~__PKVM_PAGE_RESERVED)
 
 #define PKVM_PAGE_STATE_PROT_MASK	(KVM_PGTABLE_PROT_SW0 | KVM_PGTABLE_PROT_SW1)
 static inline enum kvm_pgtable_prot pkvm_mkstate(enum kvm_pgtable_prot prot,
-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 4/7] KVM: arm64: Introduce {get,set}_host_state() helpers

[Quentin Perret]

Instead of directly accessing the host_state member in struct hyp_page,
introduce static inline accessors to do it. The future hyp_state member
will follow the same pattern as it will need some logic in the accessors.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/memory.h | 12 +++++++++++-
 arch/arm64/kvm/hyp/nvhe/mem_protect.c    | 14 +++++++-------
 arch/arm64/kvm/hyp/nvhe/setup.c          |  4 ++--
 3 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
index bf28f9f9de65..a1754aecf8f8 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
@@ -52,7 +52,7 @@ struct hyp_page {
 	u8 order;
 
 	/* Host state. Guarded by the host stage-2 lock. */
-	enum pkvm_page_state host_state : 8;
+	unsigned __host_state : 8;
 
 	u32 host_share_guest_count;
 };
@@ -89,6 +89,16 @@ static inline struct hyp_page *hyp_phys_to_page(phys_addr_t phys)
 #define hyp_page_to_virt(page)	__hyp_va(hyp_page_to_phys(page))
 #define hyp_page_to_pool(page)	(((struct hyp_page *)page)->pool)
 
+static inline enum pkvm_page_state get_host_state(phys_addr_t phys)
+{
+	return (enum pkvm_page_state)hyp_phys_to_page(phys)->__host_state;
+}
+
+static inline void set_host_state(phys_addr_t phys, enum pkvm_page_state state)
+{
+	hyp_phys_to_page(phys)->__host_state = state;
+}
+
 /*
  * Refcounting for 'struct hyp_page'.
  * hyp_pool::lock must be held if atomic access to the refcount is required.
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 2a5284f749b4..e9060e6205cb 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -467,7 +467,7 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range)
 		return -EAGAIN;
 
 	if (pte) {
-		WARN_ON(addr_is_memory(addr) && hyp_phys_to_page(addr)->host_state != PKVM_NOPAGE);
+		WARN_ON(addr_is_memory(addr) && get_host_state(addr) != PKVM_NOPAGE);
 		return -EPERM;
 	}
 
@@ -496,7 +496,7 @@ static void __host_update_page_state(phys_addr_t addr, u64 size, enum pkvm_page_
 	phys_addr_t end = addr + size;
 
 	for (; addr < end; addr += PAGE_SIZE)
-		hyp_phys_to_page(addr)->host_state = state;
+		set_host_state(addr, state);
 }
 
 int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id)
@@ -627,7 +627,7 @@ static int __host_check_page_state_range(u64 addr, u64 size,
 
 	hyp_assert_lock_held(&host_mmu.lock);
 	for (; addr < end; addr += PAGE_SIZE) {
-		if (hyp_phys_to_page(addr)->host_state != state)
+		if (get_host_state(addr) != state)
 			return -EPERM;
 	}
 
@@ -637,7 +637,7 @@ static int __host_check_page_state_range(u64 addr, u64 size,
 static int __host_set_page_state_range(u64 addr, u64 size,
 				       enum pkvm_page_state state)
 {
-	if (hyp_phys_to_page(addr)->host_state == PKVM_NOPAGE) {
+	if (get_host_state(addr) == PKVM_NOPAGE) {
 		int ret = host_stage2_idmap_locked(addr, size, PKVM_HOST_MEM_PROT);
 
 		if (ret)
@@ -911,7 +911,7 @@ int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu,
 		goto unlock;
 
 	page = hyp_phys_to_page(phys);
-	switch (page->host_state) {
+	switch (get_host_state(phys)) {
 	case PKVM_PAGE_OWNED:
 		WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_OWNED));
 		break;
@@ -964,9 +964,9 @@ static int __check_host_shared_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ip
 	if (WARN_ON(ret))
 		return ret;
 
-	page = hyp_phys_to_page(phys);
-	if (page->host_state != PKVM_PAGE_SHARED_OWNED)
+	if (get_host_state(phys) != PKVM_PAGE_SHARED_OWNED)
 		return -EPERM;
+	page = hyp_phys_to_page(phys);
 	if (WARN_ON(!page->host_share_guest_count))
 		return -EINVAL;
 
diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index d62bcb5634a2..1a414288fe8c 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -201,10 +201,10 @@ static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx,
 	case PKVM_PAGE_OWNED:
 		return host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_HYP);
 	case PKVM_PAGE_SHARED_OWNED:
-		hyp_phys_to_page(phys)->host_state = PKVM_PAGE_SHARED_BORROWED;
+		set_host_state(phys, PKVM_PAGE_SHARED_BORROWED);
 		break;
 	case PKVM_PAGE_SHARED_BORROWED:
-		hyp_phys_to_page(phys)->host_state = PKVM_PAGE_SHARED_OWNED;
+		set_host_state(phys, PKVM_PAGE_SHARED_OWNED);
 		break;
 	default:
 		return -EINVAL;
-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 5/7] KVM: arm64: Move hyp state to hyp_vmemmap

[Quentin Perret]

Tracking the hypervisor's ownership state into struct hyp_page has
several benefits, including allowing far more efficient lookups (no
page-table walk needed) and de-corelating the state from the presence
of a mapping. This will later allow to map pages into EL2 stage-1 less
proactively which is generally a good thing for security. And in the
future this will help with tracking the state of pages mapped into the
hypervisor's private range without requiring an alias into the 'linear
map' range.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/include/nvhe/memory.h | 29 +++++++++++---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c    | 51 ++++++++++++------------
 arch/arm64/kvm/hyp/nvhe/setup.c          |  6 ++-
 3 files changed, 53 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
index a1754aecf8f8..eb0c2ebd1743 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
@@ -16,8 +16,7 @@
  *       accessible by another component;
  *   10: The page is accessible but not owned by the component;
  * The storage of this state depends on the component: either in the
- * hyp_vmemmap for the host state or in PTE software bits for the hypervisor
- * and guests.
+ * hyp_vmemmap for the host and hyp states or in PTE software bits for guests.
  */
 enum pkvm_page_state {
 	PKVM_PAGE_OWNED			= 0ULL,
@@ -25,13 +24,14 @@ enum pkvm_page_state {
 	PKVM_PAGE_SHARED_BORROWED	= BIT(1),
 
 	/*
-	 * 'Meta-states' are not stored directly in PTE SW bits for hyp and
-	 * guest states, but inferred from the context (e.g. invalid PTE
-	 * entries). For the host, meta-states are stored directly in the
+	 * 'Meta-states' are not stored directly in PTE SW bits for guest
+	 * states, but inferred from the context (e.g. invalid PTE entries).
+	 * For the host and hyp, meta-states are stored directly in the
 	 * struct hyp_page.
 	 */
 	PKVM_NOPAGE			= BIT(0) | BIT(1),
 };
+#define PKVM_PAGE_STATE_MASK		(BIT(0) | BIT(1))
 
 #define PKVM_PAGE_STATE_PROT_MASK	(KVM_PGTABLE_PROT_SW0 | KVM_PGTABLE_PROT_SW1)
 static inline enum kvm_pgtable_prot pkvm_mkstate(enum kvm_pgtable_prot prot,
@@ -52,7 +52,14 @@ struct hyp_page {
 	u8 order;
 
 	/* Host state. Guarded by the host stage-2 lock. */
-	unsigned __host_state : 8;
+	unsigned __host_state : 4;
+
+	/*
+	 * Complement of the hyp state. Guarded by the hyp stage-1 lock. We use
+	 * the complement so that the initial 0 in __hyp_state_comp (due to the
+	 * entire vmemmap starting off zeroed) encodes PKVM_NOPAGE.
+	 */
+	unsigned __hyp_state_comp : 4;
 
 	u32 host_share_guest_count;
 };
@@ -99,6 +106,16 @@ static inline void set_host_state(phys_addr_t phys, enum pkvm_page_state state)
 	hyp_phys_to_page(phys)->__host_state = state;
 }
 
+static inline enum pkvm_page_state get_hyp_state(phys_addr_t phys)
+{
+	return hyp_phys_to_page(phys)->__hyp_state_comp ^ PKVM_PAGE_STATE_MASK;
+}
+
+static inline void set_hyp_state(phys_addr_t phys, enum pkvm_page_state state)
+{
+	hyp_phys_to_page(phys)->__hyp_state_comp = state ^ PKVM_PAGE_STATE_MASK;
+}
+
 /*
  * Refcounting for 'struct hyp_page'.
  * hyp_pool::lock must be held if atomic access to the refcount is required.
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index e9060e6205cb..25ff84c053c1 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -649,24 +649,24 @@ static int __host_set_page_state_range(u64 addr, u64 size,
 	return 0;
 }
 
-static enum pkvm_page_state hyp_get_page_state(kvm_pte_t pte, u64 addr)
+static void __hyp_set_page_state_range(phys_addr_t phys, u64 size, enum pkvm_page_state state)
 {
-	if (!kvm_pte_valid(pte))
-		return PKVM_NOPAGE;
+	phys_addr_t end = phys + size;
 
-	return pkvm_getstate(kvm_pgtable_hyp_pte_prot(pte));
+	for (; phys < end; phys += PAGE_SIZE)
+		set_hyp_state(phys, state);
 }
 
-static int __hyp_check_page_state_range(u64 addr, u64 size,
-					enum pkvm_page_state state)
+static int __hyp_check_page_state_range(phys_addr_t phys, u64 size, enum pkvm_page_state state)
 {
-	struct check_walk_data d = {
-		.desired	= state,
-		.get_page_state	= hyp_get_page_state,
-	};
+	phys_addr_t end = phys + size;
+
+	for (; phys < end; phys += PAGE_SIZE) {
+		if (get_hyp_state(phys) != state)
+			return -EPERM;
+	}
 
-	hyp_assert_lock_held(&pkvm_pgd_lock);
-	return check_page_state_range(&pkvm_pgtable, addr, size, &d);
+	return 0;
 }
 
 static enum pkvm_page_state guest_get_page_state(kvm_pte_t pte, u64 addr)
@@ -694,7 +694,6 @@ int __pkvm_host_share_hyp(u64 pfn)
 {
 	u64 phys = hyp_pfn_to_phys(pfn);
 	void *virt = __hyp_va(phys);
-	enum kvm_pgtable_prot prot;
 	u64 size = PAGE_SIZE;
 	int ret;
 
@@ -705,13 +704,13 @@ int __pkvm_host_share_hyp(u64 pfn)
 	if (ret)
 		goto unlock;
 	if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
-		ret = __hyp_check_page_state_range((u64)virt, size, PKVM_NOPAGE);
+		ret = __hyp_check_page_state_range(phys, size, PKVM_NOPAGE);
 		if (ret)
 			goto unlock;
 	}
 
-	prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
-	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, prot));
+	__hyp_set_page_state_range(phys, size, PKVM_PAGE_SHARED_BORROWED);
+	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, PAGE_HYP));
 	WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED));
 
 unlock:
@@ -734,7 +733,7 @@ int __pkvm_host_unshare_hyp(u64 pfn)
 	ret = __host_check_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED);
 	if (ret)
 		goto unlock;
-	ret = __hyp_check_page_state_range(virt, size, PKVM_PAGE_SHARED_BORROWED);
+	ret = __hyp_check_page_state_range(phys, size, PKVM_PAGE_SHARED_BORROWED);
 	if (ret)
 		goto unlock;
 	if (hyp_page_count((void *)virt)) {
@@ -742,6 +741,7 @@ int __pkvm_host_unshare_hyp(u64 pfn)
 		goto unlock;
 	}
 
+	__hyp_set_page_state_range(phys, size, PKVM_NOPAGE);
 	WARN_ON(kvm_pgtable_hyp_unmap(&pkvm_pgtable, virt, size) != size);
 	WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_OWNED));
 
@@ -757,7 +757,6 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
 	u64 phys = hyp_pfn_to_phys(pfn);
 	u64 size = PAGE_SIZE * nr_pages;
 	void *virt = __hyp_va(phys);
-	enum kvm_pgtable_prot prot;
 	int ret;
 
 	host_lock_component();
@@ -767,13 +766,13 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
 	if (ret)
 		goto unlock;
 	if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
-		ret = __hyp_check_page_state_range((u64)virt, size, PKVM_NOPAGE);
+		ret = __hyp_check_page_state_range(phys, size, PKVM_NOPAGE);
 		if (ret)
 			goto unlock;
 	}
 
-	prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_OWNED);
-	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, prot));
+	__hyp_set_page_state_range(phys, size, PKVM_PAGE_OWNED);
+	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, PAGE_HYP));
 	WARN_ON(host_stage2_set_owner_locked(phys, size, PKVM_ID_HYP));
 
 unlock:
@@ -793,7 +792,7 @@ int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages)
 	host_lock_component();
 	hyp_lock_component();
 
-	ret = __hyp_check_page_state_range(virt, size, PKVM_PAGE_OWNED);
+	ret = __hyp_check_page_state_range(phys, size, PKVM_PAGE_OWNED);
 	if (ret)
 		goto unlock;
 	if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
@@ -802,6 +801,7 @@ int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages)
 			goto unlock;
 	}
 
+	__hyp_set_page_state_range(phys, size, PKVM_NOPAGE);
 	WARN_ON(kvm_pgtable_hyp_unmap(&pkvm_pgtable, virt, size) != size);
 	WARN_ON(host_stage2_set_owner_locked(phys, size, PKVM_ID_HOST));
 
@@ -816,19 +816,18 @@ int hyp_pin_shared_mem(void *from, void *to)
 {
 	u64 cur, start = ALIGN_DOWN((u64)from, PAGE_SIZE);
 	u64 end = PAGE_ALIGN((u64)to);
+	u64 phys = __hyp_pa(start);
 	u64 size = end - start;
 	int ret;
 
 	host_lock_component();
 	hyp_lock_component();
 
-	ret = __host_check_page_state_range(__hyp_pa(start), size,
-					    PKVM_PAGE_SHARED_OWNED);
+	ret = __host_check_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED);
 	if (ret)
 		goto unlock;
 
-	ret = __hyp_check_page_state_range(start, size,
-					   PKVM_PAGE_SHARED_BORROWED);
+	ret = __hyp_check_page_state_range(phys, size, PKVM_PAGE_SHARED_BORROWED);
 	if (ret)
 		goto unlock;
 
diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index 1a414288fe8c..955c431af5d0 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -194,16 +194,20 @@ static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx,
 
 	/*
 	 * Adjust the host stage-2 mappings to match the ownership attributes
-	 * configured in the hypervisor stage-1.
+	 * configured in the hypervisor stage-1, and make sure to propagate them
+	 * to the hyp_vmemmap state.
 	 */
 	state = pkvm_getstate(kvm_pgtable_hyp_pte_prot(ctx->old));
 	switch (state) {
 	case PKVM_PAGE_OWNED:
+		set_hyp_state(phys, PKVM_PAGE_OWNED);
 		return host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_HYP);
 	case PKVM_PAGE_SHARED_OWNED:
+		set_hyp_state(phys, PKVM_PAGE_SHARED_OWNED);
 		set_host_state(phys, PKVM_PAGE_SHARED_BORROWED);
 		break;
 	case PKVM_PAGE_SHARED_BORROWED:
+		set_hyp_state(phys, PKVM_PAGE_SHARED_BORROWED);
 		set_host_state(phys, PKVM_PAGE_SHARED_OWNED);
 		break;
 	default:
-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 6/7] KVM: arm64: Defer EL2 stage-1 mapping on share

[Quentin Perret]

We currently blindly map into EL2 stage-1 *any* page passed to the
__pkvm_host_share_hyp() HVC. This is less than ideal from a security
perspective as it makes exploitation of potential hypervisor gadgets
easier than it should be. But interestingly, pKVM should never need to
access SHARED_BORROWED pages that it hasn't previously pinned, so there
is no need to map the page before that.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 25ff84c053c1..91b757e3fb4c 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -693,7 +693,6 @@ static int __guest_check_page_state_range(struct pkvm_hyp_vcpu *vcpu, u64 addr,
 int __pkvm_host_share_hyp(u64 pfn)
 {
 	u64 phys = hyp_pfn_to_phys(pfn);
-	void *virt = __hyp_va(phys);
 	u64 size = PAGE_SIZE;
 	int ret;
 
@@ -710,7 +709,6 @@ int __pkvm_host_share_hyp(u64 pfn)
 	}
 
 	__hyp_set_page_state_range(phys, size, PKVM_PAGE_SHARED_BORROWED);
-	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, PAGE_HYP));
 	WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED));
 
 unlock:
@@ -742,7 +740,6 @@ int __pkvm_host_unshare_hyp(u64 pfn)
 	}
 
 	__hyp_set_page_state_range(phys, size, PKVM_NOPAGE);
-	WARN_ON(kvm_pgtable_hyp_unmap(&pkvm_pgtable, virt, size) != size);
 	WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_OWNED));
 
 unlock:
@@ -818,6 +815,7 @@ int hyp_pin_shared_mem(void *from, void *to)
 	u64 end = PAGE_ALIGN((u64)to);
 	u64 phys = __hyp_pa(start);
 	u64 size = end - start;
+	struct hyp_page *p;
 	int ret;
 
 	host_lock_component();
@@ -831,8 +829,14 @@ int hyp_pin_shared_mem(void *from, void *to)
 	if (ret)
 		goto unlock;
 
-	for (cur = start; cur < end; cur += PAGE_SIZE)
-		hyp_page_ref_inc(hyp_virt_to_page(cur));
+	for (cur = start; cur < end; cur += PAGE_SIZE) {
+		p = hyp_virt_to_page(cur);
+		hyp_page_ref_inc(p);
+		if (p->refcount == 1)
+			WARN_ON(pkvm_create_mappings_locked((void *)cur,
+							    (void *)cur + PAGE_SIZE,
+							    PAGE_HYP));
+	}
 
 unlock:
 	hyp_unlock_component();
@@ -845,12 +849,17 @@ void hyp_unpin_shared_mem(void *from, void *to)
 {
 	u64 cur, start = ALIGN_DOWN((u64)from, PAGE_SIZE);
 	u64 end = PAGE_ALIGN((u64)to);
+	struct hyp_page *p;
 
 	host_lock_component();
 	hyp_lock_component();
 
-	for (cur = start; cur < end; cur += PAGE_SIZE)
-		hyp_page_ref_dec(hyp_virt_to_page(cur));
+	for (cur = start; cur < end; cur += PAGE_SIZE) {
+		p = hyp_virt_to_page(cur);
+		if (p->refcount == 1)
+			WARN_ON(kvm_pgtable_hyp_unmap(&pkvm_pgtable, cur, PAGE_SIZE) != PAGE_SIZE);
+		hyp_page_ref_dec(p);
+	}
 
 	hyp_unlock_component();
 	host_unlock_component();
-- 
2.49.0.604.gff1f9ca942-goog

[PATCH v2 7/7] KVM: arm64: Unconditionally cross check hyp state

[Quentin Perret]

Now that the hypervisor's state is stored in the hyp_vmemmap, we no
longer need an expensive page-table walk to read it. This means we can
now afford to cross check the hyp-state during all memory ownership
transitions where the hyp is involved unconditionally, hence avoiding
problems such as [1].

[1] https://lore.kernel.org/kvmarm/20241128154406.602875-1-qperret@google.com/

Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 91b757e3fb4c..709d286999a1 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -702,11 +702,9 @@ int __pkvm_host_share_hyp(u64 pfn)
 	ret = __host_check_page_state_range(phys, size, PKVM_PAGE_OWNED);
 	if (ret)
 		goto unlock;
-	if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
-		ret = __hyp_check_page_state_range(phys, size, PKVM_NOPAGE);
-		if (ret)
-			goto unlock;
-	}
+	ret = __hyp_check_page_state_range(phys, size, PKVM_NOPAGE);
+	if (ret)
+		goto unlock;
 
 	__hyp_set_page_state_range(phys, size, PKVM_PAGE_SHARED_BORROWED);
 	WARN_ON(__host_set_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED));
@@ -762,11 +760,9 @@ int __pkvm_host_donate_hyp(u64 pfn, u64 nr_pages)
 	ret = __host_check_page_state_range(phys, size, PKVM_PAGE_OWNED);
 	if (ret)
 		goto unlock;
-	if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
-		ret = __hyp_check_page_state_range(phys, size, PKVM_NOPAGE);
-		if (ret)
-			goto unlock;
-	}
+	ret = __hyp_check_page_state_range(phys, size, PKVM_NOPAGE);
+	if (ret)
+		goto unlock;
 
 	__hyp_set_page_state_range(phys, size, PKVM_PAGE_OWNED);
 	WARN_ON(pkvm_create_mappings_locked(virt, virt + size, PAGE_HYP));
@@ -792,11 +788,9 @@ int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages)
 	ret = __hyp_check_page_state_range(phys, size, PKVM_PAGE_OWNED);
 	if (ret)
 		goto unlock;
-	if (IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
-		ret = __host_check_page_state_range(phys, size, PKVM_NOPAGE);
-		if (ret)
-			goto unlock;
-	}
+	ret = __host_check_page_state_range(phys, size, PKVM_NOPAGE);
+	if (ret)
+		goto unlock;
 
 	__hyp_set_page_state_range(phys, size, PKVM_NOPAGE);
 	WARN_ON(kvm_pgtable_hyp_unmap(&pkvm_pgtable, virt, size) != size);
-- 
2.49.0.604.gff1f9ca942-goog

Re: [PATCH v2 0/7] Move pKVM ownership state to hyp_vmemmap

[Marc Zyngier]

On Wed, 16 Apr 2025 15:26:40 +0000, Quentin Perret wrote:
> This series moves the hypervisor's ownership state to the hyp_vmemmap,
> as discussed in [1]. The two main benefits are:
> 
>  1. much cheaper hyp state lookups, since we can avoid the hyp stage-1
>     page-table walk;
> 
>  2. de-correlates the hyp state from the presence of a mapping in the
>     linear map range of the hypervisor; which enables a bunch of
>     clean-ups in the existing code and will simplify the introduction of
>     other features in the future (hyp tracing, ...)
> 
> [...]

Applied to next, thanks!

[1/7] KVM: arm64: Track SVE state in the hypervisor vcpu structure
      commit: 5db1bef933427aa467ad89c7b695a84a6b4afe16
[2/7] KVM: arm64: Fix pKVM page-tracking comments
      commit: ba637018ca67224fa21dc2212cb4457b357a5455
[3/7] KVM: arm64: Use 0b11 for encoding PKVM_NOPAGE
      commit: cd4b039165a5e709d0d599e207709d73141a8bed
[4/7] KVM: arm64: Introduce {get,set}_host_state() helpers
      commit: ba5b2e5b9dff5ba14940e1525f6e3a595f012466
[5/7] KVM: arm64: Move hyp state to hyp_vmemmap
      commit: 3390b3cbb613bc0822854f5754437cd1d1b3d5d0
[6/7] KVM: arm64: Defer EL2 stage-1 mapping on share
      commit: 48d848882395a6a42ff1bb685082c79791d4e753
[7/7] KVM: arm64: Unconditionally cross check hyp state
      commit: 43c475504a39e98f10f5e6ec4d9d9ed60672a753

Cheers,

	M.
-- 
Without deviation from the norm, progress is not possible.