linux-kernel - [RFC PATCH 5/7] kvm: arm64: Modify stage2 young mechanism to support hw DBM

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Date:   Mon, 25 May 2020 19:24:04 +0800
From:   Keqian Zhu <zhukeqian1@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>
CC:     Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Will Deacon <will@...nel.org>,
        "Suzuki K Poulose" <suzuki.poulose@....com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Mark Brown <broonie@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexios Zavras <alexios.zavras@...el.com>,
        <wanghaibin.wang@...wei.com>, <zhengxiang9@...wei.com>,
        Keqian Zhu <zhukeqian1@...wei.com>
Subject: [RFC PATCH 5/7] kvm: arm64: Modify stage2 young mechanism to support hw DBM

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@...wei.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