[PATCH] KVM: riscv: Age all G-stage PTEs in a GFN range

[PATCH] KVM: riscv: Age all G-stage PTEs in a GFN range

[SeungJu Cheon]

kvm_age_gfn() and kvm_test_age_gfn() only operate on the G-stage
leaf covering range->start. They also warn unless the range size is
exactly 4K, 2M, or 1G.

The MM can pass larger ranges when batching the PTEs of a large folio.
For example, a 64K mTHP range triggers the warning and only the first
4K leaf is aged, leaving the Accessed bits of the remaining leaves
unchanged.

This can be reproduced on an rv64 host with Svadu by disabling 2M THP,
enabling 64K mTHP, and running:

access_tracking_perf_test -s anonymous_thp

This results in:

WARNING: arch/riscv/kvm/mmu.c:362 at kvm_age_gfn+0x210/0x370
...
[<ffffffff800c8fc8>] kvm_age_gfn+0x210/0x370
[<ffffffff80095c90>] kvm_mmu_notifier_clear_young+0x250/0x478
[<ffffffff80ae532e>] __mmu_notifier_clear_young+0xde/0x1a0
[<ffffffff80932f76>] walk_pud_range+0x86e/0x1688
[<ffffffff80a18720>] walk_pgd_range+0x518/0x17b0
[<ffffffff80a19aa2>] __walk_page_range+0xea/0x580
[<ffffffff80a1a422>] walk_page_range+0x3a/0x80
[<ffffffff80931dc0>] try_to_inc_max_seq+0x520/0xe68
[<ffffffff80939dc0>] lru_gen_seq_write+0xd08/0x1310

Walk all G-stage leaves in the requested range. Advance by the leaf
size when a mapping is found, or by the size of the non-present region
at the level where the walk stopped. When testing the age, return as
soon as a young leaf is found.

Remove the range-size warning since arbitrary GFN ranges are valid.

Fixes: 9955371cc014 ("RISC-V: KVM: Implement MMU notifiers")
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
---
 arch/riscv/include/asm/kvm_gstage.h |  2 ++
 arch/riscv/kvm/gstage.c             | 34 +++++++++++++++++++++++++++++
 arch/riscv/kvm/mmu.c                | 22 ++++---------------
 3 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_gstage.h b/arch/riscv/include/asm/kvm_gstage.h
index aaf080ba1b77..a03db1a10095 100644
--- a/arch/riscv/include/asm/kvm_gstage.h
+++ b/arch/riscv/include/asm/kvm_gstage.h
@@ -81,6 +81,8 @@ bool kvm_riscv_gstage_unmap_range(struct kvm_gstage *gstage,
 				  gpa_t start, gpa_t size, bool may_block);
 
 bool kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end);
+bool kvm_riscv_gstage_age_range(struct kvm_gstage *gstage, gpa_t start,
+				gpa_t end, bool test_only);
 
 bool kvm_riscv_gstage_wp_pt_masked(struct kvm_gstage *gstage, gfn_t base_gfn,
 				   unsigned long mask);
diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index e5002cb9cbef..f61ba434093c 100644
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -485,6 +485,40 @@ bool kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
 	return flush;
 }
 
+bool kvm_riscv_gstage_age_range(struct kvm_gstage *gstage, gpa_t start,
+				gpa_t end, bool test_only)
+{
+	unsigned long page_size;
+	bool young = false;
+	gpa_t addr = start;
+	pte_t *ptep;
+	u32 level;
+	bool found;
+
+	while (addr < end) {
+		found = kvm_riscv_gstage_get_leaf(gstage, addr, &ptep, &level);
+		if (gstage_level_to_page_size(gstage, level, &page_size))
+			break;
+
+		if (found) {
+			if (test_only) {
+				if (pte_young(ptep_get(ptep)))
+					return true;
+			} else {
+				young |= ptep_test_and_clear_young(NULL, 0, ptep);
+			}
+		}
+
+		/*
+		 * Advance past this leaf, or past the non-present region at
+		 * the level where the walk stopped.
+		 */
+		addr = ALIGN_DOWN(addr, page_size) + page_size;
+	}
+
+	return young;
+}
+
 static inline void clear_huge_mask(unsigned long *mask, unsigned long page_size,
 				   gfn_t base_gfn, gpa_t addr)
 {
diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 3e955d808743..342f606399e5 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -351,42 +351,28 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
 
 bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 {
-	pte_t *ptep;
-	u32 ptep_level = 0;
-	u64 size = (range->end - range->start) << PAGE_SHIFT;
 	struct kvm_gstage gstage;
 
 	if (!kvm->arch.pgd)
 		return false;
 
-	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
-
 	kvm_riscv_gstage_init(&gstage, kvm);
-	if (!kvm_riscv_gstage_get_leaf(&gstage, range->start << PAGE_SHIFT,
-				       &ptep, &ptep_level))
-		return false;
 
-	return ptep_test_and_clear_young(NULL, 0, ptep);
+	return kvm_riscv_gstage_age_range(&gstage, range->start << PAGE_SHIFT,
+					  range->end << PAGE_SHIFT, false);
 }
 
 bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 {
-	pte_t *ptep;
-	u32 ptep_level = 0;
-	u64 size = (range->end - range->start) << PAGE_SHIFT;
 	struct kvm_gstage gstage;
 
 	if (!kvm->arch.pgd)
 		return false;
 
-	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
-
 	kvm_riscv_gstage_init(&gstage, kvm);
-	if (!kvm_riscv_gstage_get_leaf(&gstage, range->start << PAGE_SHIFT,
-				       &ptep, &ptep_level))
-		return false;
 
-	return pte_young(ptep_get(ptep));
+	return kvm_riscv_gstage_age_range(&gstage, range->start << PAGE_SHIFT,
+					  range->end << PAGE_SHIFT, true);
 }
 
 static bool fault_supports_gstage_huge_mapping(struct kvm_memory_slot *memslot,

base-commit: 41e81f7e3ef96594fb840445343c0ee7723aa550
-- 
2.52.0