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From: Jinyu Tang <jinyu.tang@linux.dev>
To: SeungJu Cheon <suunj1331@gmail.com>
Cc: Jinyu Tang <jinyu.tang@linux.dev>,
	anup@brainfault.org, atish.patra@linux.dev, tjytimi@163.com,
	inochiama@gmail.com, pjw@kernel.org, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, alex@ghiti.fr, andrew.jones@linux.dev,
	pbonzini@redhat.com, seanjc@google.com,
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] KVM: riscv: Set Accessed bit in dirty-log write fault fast path
Date: Wed, 21 Oct 2026 19:30:10 +0800	[thread overview]
Message-ID: <20261021113010.2476783-1-jinyu.tang@linux.dev> (raw)
In-Reply-To: <20261016101458.221648-1-suunj1331@gmail.com>

On Fri, Oct 16, 2026 at 07:14:58PM +0900, SeungJu Cheon wrote:
> @@ -591,14 +591,15 @@ static bool kvm_riscv_mmu_dirty_log_write_fault_fast(struct kvm *kvm,
>  			dirty_marked = true;
>  		}
>  
> -		if ((pte_val(old_pte) & (_PAGE_WRITE | _PAGE_DIRTY)) ==
> -		    (_PAGE_WRITE | _PAGE_DIRTY)) {
> +		if ((pte_val(old_pte) &
> +		     (_PAGE_WRITE | _PAGE_DIRTY | _PAGE_ACCESSED)) ==
> +		    (_PAGE_WRITE | _PAGE_DIRTY | _PAGE_ACCESSED)) {
>  			new_pte = old_pte;
>  			ret = true;
>  			break;
>  		}
>  
> -		new_pte = pte_mkdirty(pte_mkwrite_novma(old_pte));
> +		new_pte = pte_mkyoung(pte_mkdirty(pte_mkwrite_novma(old_pte)));

I tested this on QEMU 10.2.1 with Svade enabled and Svadu disabled.
With dirty logging enabled, the test clears A through page-idle tracking,
write-protects the page with KVM_GET_DIRTY_LOG, and resumes the guest
write. The unpatched kernel times out after 10 seconds, while the same
test completes with this patch applied.

Reviewed-by: Jinyu Tang <jinyu.tang@linux.dev>

Thanks,
Jinyu

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Jinyu Tang <jinyu.tang@linux.dev>
To: SeungJu Cheon <suunj1331@gmail.com>
Cc: Jinyu Tang <jinyu.tang@linux.dev>,
	anup@brainfault.org, atish.patra@linux.dev, tjytimi@163.com,
	inochiama@gmail.com, pjw@kernel.org, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, alex@ghiti.fr, andrew.jones@linux.dev,
	pbonzini@redhat.com, seanjc@google.com,
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] KVM: riscv: Set Accessed bit in dirty-log write fault fast path
Date: Wed, 21 Oct 2026 19:30:10 +0800	[thread overview]
Message-ID: <20261021113010.2476783-1-jinyu.tang@linux.dev> (raw)
In-Reply-To: <20261016101458.221648-1-suunj1331@gmail.com>

On Fri, Oct 16, 2026 at 07:14:58PM +0900, SeungJu Cheon wrote:
> @@ -591,14 +591,15 @@ static bool kvm_riscv_mmu_dirty_log_write_fault_fast(struct kvm *kvm,
>  			dirty_marked = true;
>  		}
>  
> -		if ((pte_val(old_pte) & (_PAGE_WRITE | _PAGE_DIRTY)) ==
> -		    (_PAGE_WRITE | _PAGE_DIRTY)) {
> +		if ((pte_val(old_pte) &
> +		     (_PAGE_WRITE | _PAGE_DIRTY | _PAGE_ACCESSED)) ==
> +		    (_PAGE_WRITE | _PAGE_DIRTY | _PAGE_ACCESSED)) {
>  			new_pte = old_pte;
>  			ret = true;
>  			break;
>  		}
>  
> -		new_pte = pte_mkdirty(pte_mkwrite_novma(old_pte));
> +		new_pte = pte_mkyoung(pte_mkdirty(pte_mkwrite_novma(old_pte)));

I tested this on QEMU 10.2.1 with Svade enabled and Svadu disabled.
With dirty logging enabled, the test clears A through page-idle tracking,
write-protects the page with KVM_GET_DIRTY_LOG, and resumes the guest
write. The unpatched kernel times out after 10 seconds, while the same
test completes with this patch applied.

Reviewed-by: Jinyu Tang <jinyu.tang@linux.dev>

Thanks,
Jinyu

-- 
kvm-riscv mailing list
kvm-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kvm-riscv

WARNING: multiple messages have this Message-ID (diff)
From: Jinyu Tang <jinyu.tang@linux.dev>
To: SeungJu Cheon <suunj1331@gmail.com>
Cc: Jinyu Tang <jinyu.tang@linux.dev>,
	anup@brainfault.org, atish.patra@linux.dev, tjytimi@163.com,
	inochiama@gmail.com, pjw@kernel.org, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, alex@ghiti.fr, andrew.jones@linux.dev,
	pbonzini@redhat.com, seanjc@google.com,
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] KVM: riscv: Set Accessed bit in dirty-log write fault fast path
Date: Wed, 21 Oct 2026 19:30:10 +0800	[thread overview]
Message-ID: <20261021113010.2476783-1-jinyu.tang@linux.dev> (raw)
In-Reply-To: <20261016101458.221648-1-suunj1331@gmail.com>

On Fri, Oct 16, 2026 at 07:14:58PM +0900, SeungJu Cheon wrote:
> @@ -591,14 +591,15 @@ static bool kvm_riscv_mmu_dirty_log_write_fault_fast(struct kvm *kvm,
>  			dirty_marked = true;
>  		}
>  
> -		if ((pte_val(old_pte) & (_PAGE_WRITE | _PAGE_DIRTY)) ==
> -		    (_PAGE_WRITE | _PAGE_DIRTY)) {
> +		if ((pte_val(old_pte) &
> +		     (_PAGE_WRITE | _PAGE_DIRTY | _PAGE_ACCESSED)) ==
> +		    (_PAGE_WRITE | _PAGE_DIRTY | _PAGE_ACCESSED)) {
>  			new_pte = old_pte;
>  			ret = true;
>  			break;
>  		}
>  
> -		new_pte = pte_mkdirty(pte_mkwrite_novma(old_pte));
> +		new_pte = pte_mkyoung(pte_mkdirty(pte_mkwrite_novma(old_pte)));

I tested this on QEMU 10.2.1 with Svade enabled and Svadu disabled.
With dirty logging enabled, the test clears A through page-idle tracking,
write-protects the page with KVM_GET_DIRTY_LOG, and resumes the guest
write. The unpatched kernel times out after 10 seconds, while the same
test completes with this patch applied.

Reviewed-by: Jinyu Tang <jinyu.tang@linux.dev>

Thanks,
Jinyu

  parent reply	other threads:[~2026-10-21 11:31 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-16 10:14 [PATCH] KVM: riscv: Set Accessed bit in dirty-log write fault fast path SeungJu Cheon
2026-10-16 10:14 ` SeungJu Cheon
2026-10-16 10:14 ` SeungJu Cheon
2026-10-16 10:26 ` sashiko-bot
2026-10-21 11:30 ` Jinyu Tang [this message]
2026-10-21 11:30   ` Jinyu Tang
2026-10-21 11:30   ` Jinyu Tang

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