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Subject[RFC PATCH 5/7] kvm: arm64: Modify stage2 young mechanism to support hw DBM
Date
Making page table entries young (set AF bit) should be atomic to
avoid cover dirty info that is set by hardware.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
---
arch/arm64/include/asm/kvm_mmu.h | 32 ++++++++++++++++++++++----------
virt/kvm/arm/mmu.c | 10 +++++-----
2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 8df078f0ee67..a4620d87e456 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -235,6 +235,18 @@ static inline void kvm_set_s2pte_readonly(pte_t *ptep)
} while (pteval != old_pteval);
}

+static inline void kvm_set_s2pte_young(pte_t *ptep)
+{
+ pteval_t old_pteval, pteval;
+
+ pteval = READ_ONCE(pte_val(*ptep));
+ do {
+ old_pteval = pteval;
+ pteval |= PTE_AF;
+ pteval = cmpxchg_relaxed(&pte_val(*ptep), old_pteval, pteval);
+ } while (pteval != old_pteval);
+}
+
static inline bool kvm_s2pte_readonly(pte_t *ptep)
{
return (READ_ONCE(pte_val(*ptep)) & PTE_S2_RDWR) == PTE_S2_RDONLY;
@@ -250,6 +262,11 @@ static inline void kvm_set_s2pmd_readonly(pmd_t *pmdp)
kvm_set_s2pte_readonly((pte_t *)pmdp);
}

+static inline void kvm_set_s2pmd_young(pmd_t *pmdp)
+{
+ kvm_set_s2pte_young((pte_t *)pmdp);
+}
+
static inline bool kvm_s2pmd_readonly(pmd_t *pmdp)
{
return kvm_s2pte_readonly((pte_t *)pmdp);
@@ -265,6 +282,11 @@ static inline void kvm_set_s2pud_readonly(pud_t *pudp)
kvm_set_s2pte_readonly((pte_t *)pudp);
}

+static inline void kvm_set_s2pud_young(pud_t *pudp)
+{
+ kvm_set_s2pte_young((pte_t *)pudp);
+}
+
static inline bool kvm_s2pud_readonly(pud_t *pudp)
{
return kvm_s2pte_readonly((pte_t *)pudp);
@@ -275,16 +297,6 @@ static inline bool kvm_s2pud_exec(pud_t *pudp)
return !(READ_ONCE(pud_val(*pudp)) & PUD_S2_XN);
}

-static inline pud_t kvm_s2pud_mkyoung(pud_t pud)
-{
- return pud_mkyoung(pud);
-}
-
-static inline bool kvm_s2pud_young(pud_t pud)
-{
- return pud_young(pud);
-}
-
#ifdef CONFIG_ARM64_HW_AFDBM
static inline bool kvm_hw_dbm_enabled(void)
{
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 779859b85d6d..e1d9e4b98cb6 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1888,15 +1888,15 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
goto out;

if (pud) { /* HugeTLB */
- *pud = kvm_s2pud_mkyoung(*pud);
+ kvm_set_s2pud_young(pud);
pfn = kvm_pud_pfn(*pud);
pfn_valid = true;
} else if (pmd) { /* THP, HugeTLB */
- *pmd = pmd_mkyoung(*pmd);
+ kvm_set_s2pmd_young(pmd);
pfn = pmd_pfn(*pmd);
pfn_valid = true;
- } else {
- *pte = pte_mkyoung(*pte); /* Just a page... */
+ } else { /* Just a page... */
+ kvm_set_s2pte_young(pte);
pfn = pte_pfn(*pte);
pfn_valid = true;
}
@@ -2141,7 +2141,7 @@ static int kvm_test_age_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *
return 0;

if (pud)
- return kvm_s2pud_young(*pud);
+ return pud_young(*pud);
else if (pmd)
return pmd_young(*pmd);
else
--
2.19.1
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