linux-kernel - [PATCH v2 1/8] KVM: arm64: Set DBM bit for writable PTEs

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Date:   Thu, 2 Jul 2020 21:55:49 +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>,
        Steven Price <steven.price@....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 v2 1/8] KVM: arm64: Set DBM bit for writable PTEs

DBM bit is used by MMU to differentiate a genuinely non-writable
page from a page that is only temporarily non-writable in order
to mark dirty.

Signed-off-by: Keqian Zhu <zhukeqian1@...wei.com>
Signed-off-by: Peng Liang <liangpeng10@...wei.com>
---
 arch/arm64/include/asm/kvm_mmu.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index b12bfc1f051a..2700442b0f75 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -169,6 +169,10 @@ void kvm_clear_hyp_idmap(void);
 static inline pte_t kvm_s2pte_mkwrite(pte_t pte)
 {
 	pte_val(pte) |= PTE_S2_RDWR;
+
+	if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM))
+		pte_val(pte) |= PTE_DBM;
+
 	return pte;
 }
 
-- 
2.19.1