[PATCH 0/3] KVM: SVM: Clean up SEV-ES save area management

[PATCH 0/3] KVM: SVM: Clean up SEV-ES save area management

[Sean Christopherson]

Clean up KVM's handling of the SEV-ES host save area, and opportunistically
add a helper to dedup code for converting an SME-tweaked PA back into its
struct page.

Sean Christopherson (3):
  KVM: SVM: Add a helper to convert a SME-aware PA back to a struct page
  KVM: SVM: Add host SEV-ES save area structure into VMCB via a union
  KVM: SVM: Track the per-CPU host save area as a VMCB pointer

 arch/x86/include/asm/svm.h | 20 +++++++++++++++-----
 arch/x86/kvm/svm/svm.c     | 24 ++++++++++++------------
 arch/x86/kvm/svm/svm.h     | 18 ++++++++++++++++--
 3 files changed, 43 insertions(+), 19 deletions(-)


base-commit: 332d2c1d713e232e163386c35a3ba0c1b90df83f
-- 
2.46.0.rc2.264.g509ed76dc8-goog

[PATCH 1/3] KVM: SVM: Add a helper to convert a SME-aware PA back to a struct page

[Sean Christopherson]

Add __sme_pa_to_page() to pair with __sme_page_pa() and use it to replace
open coded equivalents, including for "iopm_base", which previously
avoided having to do __sme_clr() by storing the raw PA in the global
variable.

Opportunistically convert __sme_page_pa() to a helper to provide type
safety.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c |  9 ++++-----
 arch/x86/kvm/svm/svm.h | 16 +++++++++++++++-
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c115d26844f7..2c44261fda70 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1124,8 +1124,7 @@ static void svm_hardware_unsetup(void)
 	for_each_possible_cpu(cpu)
 		svm_cpu_uninit(cpu);
 
-	__free_pages(pfn_to_page(iopm_base >> PAGE_SHIFT),
-	get_order(IOPM_SIZE));
+	__free_pages(__sme_pa_to_page(iopm_base), get_order(IOPM_SIZE));
 	iopm_base = 0;
 }
 
@@ -1301,7 +1300,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
 	if (!kvm_hlt_in_guest(vcpu->kvm))
 		svm_set_intercept(svm, INTERCEPT_HLT);
 
-	control->iopm_base_pa = __sme_set(iopm_base);
+	control->iopm_base_pa = iopm_base;
 	control->msrpm_base_pa = __sme_set(__pa(svm->msrpm));
 	control->int_ctl = V_INTR_MASKING_MASK;
 
@@ -1503,7 +1502,7 @@ static void svm_vcpu_free(struct kvm_vcpu *vcpu)
 
 	sev_free_vcpu(vcpu);
 
-	__free_page(pfn_to_page(__sme_clr(svm->vmcb01.pa) >> PAGE_SHIFT));
+	__free_page(__sme_pa_to_page(svm->vmcb01.pa));
 	__free_pages(virt_to_page(svm->msrpm), get_order(MSRPM_SIZE));
 }
 
@@ -5250,7 +5249,7 @@ static __init int svm_hardware_setup(void)
 
 	iopm_va = page_address(iopm_pages);
 	memset(iopm_va, 0xff, PAGE_SIZE * (1 << order));
-	iopm_base = page_to_pfn(iopm_pages) << PAGE_SHIFT;
+	iopm_base = __sme_page_pa(iopm_pages);
 
 	init_msrpm_offsets();
 
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 76107c7d0595..2b095acdb97f 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -25,7 +25,21 @@
 #include "cpuid.h"
 #include "kvm_cache_regs.h"
 
-#define __sme_page_pa(x) __sme_set(page_to_pfn(x) << PAGE_SHIFT)
+/*
+ * Helpers to convert to/from physical addresses for pages whose address is
+ * consumed directly by hardware.  Even though it's a physical address, SVM
+ * often restricts the address to the natural width, hence 'unsigned long'
+ * instead of 'hpa_t'.
+ */
+static inline unsigned long __sme_page_pa(struct page *page)
+{
+	return __sme_set(page_to_pfn(page) << PAGE_SHIFT);
+}
+
+static inline struct page *__sme_pa_to_page(unsigned long pa)
+{
+	return pfn_to_page(__sme_clr(pa) >> PAGE_SHIFT);
+}
 
 #define	IOPM_SIZE PAGE_SIZE * 3
 #define	MSRPM_SIZE PAGE_SIZE * 2
-- 
2.46.0.rc2.264.g509ed76dc8-goog

[PATCH 2/3] KVM: SVM: Add host SEV-ES save area structure into VMCB via a union

[Sean Christopherson]

Incorporate the _host_ SEV-ES save area into the VMCB as a union with the
legacy save area.  The SEV-ES variant used to save/load host state is
larger than the legacy save area, but resides at the same offset.  Prefix
the field with "host" to make it as obvious as possible that the SEV-ES
variant in the VMCB is only ever used for host state.  Guest state for
SEV-ES VMs is stored in a completely separate page (VMSA), albeit with
the same layout as the host state.

Add a compile-time assert to ensure the VMCB layout is correct, i.e. that
KVM's layout matches the architectural definitions.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/include/asm/svm.h | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index f0dea3750ca9..2b59b9951c90 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -516,6 +516,20 @@ struct ghcb {
 	u32 ghcb_usage;
 } __packed;
 
+struct vmcb {
+	struct vmcb_control_area control;
+	union {
+		struct vmcb_save_area save;
+
+		/*
+		 * For SEV-ES VMs, the save area in the VMCB is used only to
+		 * save/load host state.  Guest state resides in a separate
+		 * page, the aptly named VM Save Area (VMSA), that is encrypted
+		 * with the guest's private key.
+		 */
+		struct sev_es_save_area host_sev_es_save;
+	};
+} __packed;
 
 #define EXPECTED_VMCB_SAVE_AREA_SIZE		744
 #define EXPECTED_GHCB_SAVE_AREA_SIZE		1032
@@ -532,6 +546,7 @@ static inline void __unused_size_checks(void)
 	BUILD_BUG_ON(sizeof(struct ghcb_save_area)	!= EXPECTED_GHCB_SAVE_AREA_SIZE);
 	BUILD_BUG_ON(sizeof(struct sev_es_save_area)	!= EXPECTED_SEV_ES_SAVE_AREA_SIZE);
 	BUILD_BUG_ON(sizeof(struct vmcb_control_area)	!= EXPECTED_VMCB_CONTROL_AREA_SIZE);
+	BUILD_BUG_ON(offsetof(struct vmcb, save)	!= EXPECTED_VMCB_CONTROL_AREA_SIZE);
 	BUILD_BUG_ON(sizeof(struct ghcb)		!= EXPECTED_GHCB_SIZE);
 
 	/* Check offsets of reserved fields */
@@ -568,11 +583,6 @@ static inline void __unused_size_checks(void)
 	BUILD_BUG_RESERVED_OFFSET(ghcb, 0xff0);
 }
 
-struct vmcb {
-	struct vmcb_control_area control;
-	struct vmcb_save_area save;
-} __packed;
-
 #define SVM_CPUID_FUNC 0x8000000a
 
 #define SVM_SELECTOR_S_SHIFT 4
-- 
2.46.0.rc2.264.g509ed76dc8-goog

[PATCH 3/3] KVM: SVM: Track the per-CPU host save area as a VMCB pointer

[Sean Christopherson]

The host save area is a VMCB, track it as such to help readers follow
along, but mostly to cleanup/simplify the retrieval of the SEV-ES host
save area.

Note, the compile-time assertion that

  offsetof(struct vmcb, save) == EXPECTED_VMCB_CONTROL_AREA_SIZE

ensures that the SEV-ES save area is indeed at offset 0x400 (whoever added
the expected/architectural VMCB offsets apparently likes decimal).

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/svm.c | 15 ++++++++-------
 arch/x86/kvm/svm/svm.h |  2 +-
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2c44261fda70..43156ac93fb3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -573,7 +573,7 @@ static void __svm_write_tsc_multiplier(u64 multiplier)
 
 static __always_inline struct sev_es_save_area *sev_es_host_save_area(struct svm_cpu_data *sd)
 {
-	return page_address(sd->save_area) + 0x400;
+	return &sd->save_area->host_sev_es_save;
 }
 
 static inline void kvm_cpu_svm_disable(void)
@@ -696,7 +696,7 @@ static void svm_cpu_uninit(int cpu)
 		return;
 
 	kfree(sd->sev_vmcbs);
-	__free_page(sd->save_area);
+	__free_page(__sme_pa_to_page(sd->save_area_pa));
 	sd->save_area_pa = 0;
 	sd->save_area = NULL;
 }
@@ -704,23 +704,24 @@ static void svm_cpu_uninit(int cpu)
 static int svm_cpu_init(int cpu)
 {
 	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
+	struct page *save_area_page;
 	int ret = -ENOMEM;
 
 	memset(sd, 0, sizeof(struct svm_cpu_data));
-	sd->save_area = snp_safe_alloc_page_node(cpu_to_node(cpu), GFP_KERNEL);
-	if (!sd->save_area)
+	save_area_page = snp_safe_alloc_page_node(cpu_to_node(cpu), GFP_KERNEL);
+	if (!save_area_page)
 		return ret;
 
 	ret = sev_cpu_init(sd);
 	if (ret)
 		goto free_save_area;
 
-	sd->save_area_pa = __sme_page_pa(sd->save_area);
+	sd->save_area = page_address(save_area_page);
+	sd->save_area_pa = __sme_page_pa(save_area_page);
 	return 0;
 
 free_save_area:
-	__free_page(sd->save_area);
-	sd->save_area = NULL;
+	__free_page(save_area_page);
 	return ret;
 
 }
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 2b095acdb97f..43fa6a16eb19 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -335,7 +335,7 @@ struct svm_cpu_data {
 	u32 next_asid;
 	u32 min_asid;
 
-	struct page *save_area;
+	struct vmcb *save_area;
 	unsigned long save_area_pa;
 
 	struct vmcb *current_vmcb;
-- 
2.46.0.rc2.264.g509ed76dc8-goog

Re: [PATCH 0/3] KVM: SVM: Clean up SEV-ES save area management

[Sean Christopherson]

On Fri, 02 Aug 2024 13:45:08 -0700, Sean Christopherson wrote:
> Clean up KVM's handling of the SEV-ES host save area, and opportunistically
> add a helper to dedup code for converting an SME-tweaked PA back into its
> struct page.
> 
> Sean Christopherson (3):
>   KVM: SVM: Add a helper to convert a SME-aware PA back to a struct page
>   KVM: SVM: Add host SEV-ES save area structure into VMCB via a union
>   KVM: SVM: Track the per-CPU host save area as a VMCB pointer
> 
> [...]

Applied to kvm-x86 svm, thanks!

[1/3] KVM: SVM: Add a helper to convert a SME-aware PA back to a struct page
      https://github.com/kvm-x86/linux/commit/48547fe75ea7
[2/3] KVM: SVM: Add host SEV-ES save area structure into VMCB via a union
      https://github.com/kvm-x86/linux/commit/1b5ef14dc656
[3/3] KVM: SVM: Track the per-CPU host save area as a VMCB pointer
      https://github.com/kvm-x86/linux/commit/32071fa355e7

--
https://github.com/kvm-x86/linux/tree/next