linux-kernel - [PATCH 06/12] KVM: arm64: Set DBM bit of PTEs during write protecting

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Date:   Tue, 16 Jun 2020 17:35:47 +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>,
        <liangpeng10@...wei.com>, <zhengxiang9@...wei.com>,
        <wanghaibin.wang@...wei.com>, Keqian Zhu <zhukeqian1@...wei.com>
Subject: [PATCH 06/12] KVM: arm64: Set DBM bit of PTEs during write protecting

During write protecting PTEs, if hardware dirty log is enabled,
set the DBM bit of PTEs when they are *already writable*. This
ensures some mechanisms that rely on "write fault", such as CoW,
are not broken.

Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
Signed-off-by: Peng Liang <liangpeng10@...wei.com>
---
 arch/arm64/kvm/mmu.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f08b0fbca0a0..742c7943176f 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1536,19 +1536,24 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 
 /**
  * stage2_wp_ptes - write protect PMD range
+ * @kvm:	kvm instance for the VM
  * @pmd:	pointer to pmd entry
  * @addr:	range start address
  * @end:	range end address
  */
-static void stage2_wp_ptes(pmd_t *pmd, phys_addr_t addr, phys_addr_t end)
+static void stage2_wp_ptes(struct kvm *kvm, pmd_t *pmd,
+			   phys_addr_t addr, phys_addr_t end)
 {
 	pte_t *pte;
 
 	pte = pte_offset_kernel(pmd, addr);
 	do {
-		if (!pte_none(*pte)) {
-			if (!kvm_s2pte_readonly(pte))
-				kvm_set_s2pte_readonly(pte);
+		if (!pte_none(*pte) && !kvm_s2pte_readonly(pte)) {
+#ifdef CONFIG_ARM64_HW_AFDBM
+			if (kvm->arch.hw_dirty_log && !kvm_s2pte_dbm(pte))
+				kvm_set_s2pte_dbm(pte);
+#endif
+			kvm_set_s2pte_readonly(pte);
 		}
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }
@@ -1575,7 +1580,7 @@ static void stage2_wp_pmds(struct kvm *kvm, pud_t *pud,
 				if (!kvm_s2pmd_readonly(pmd))
 					kvm_set_s2pmd_readonly(pmd);
 			} else {
-				stage2_wp_ptes(pmd, addr, next);
+				stage2_wp_ptes(kvm, pmd, addr, next);
 			}
 		}
 	} while (pmd++, addr = next, addr != end);
-- 
2.19.1