linux-kernel - Re: [PATCH v12 56/84] KVM: RISC-V: Mark "struct page" pfns dirty iff a stage-2 PTE is installed

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Message-ID: <20240731-0456655970f6ae99f907de43@orel>
Date: Wed, 31 Jul 2024 10:11:34 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Tianrui Zhao <zhaotianrui@...ngson.cn>, 
	Bibo Mao <maobibo@...ngson.cn>, Huacai Chen <chenhuacai@...nel.org>, 
	Michael Ellerman <mpe@...erman.id.au>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, loongarch@...ts.linux.dev, 
	linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	David Matlack <dmatlack@...gle.com>, David Stevens <stevensd@...omium.org>
Subject: Re: [PATCH v12 56/84] KVM: RISC-V: Mark "struct page" pfns dirty iff
 a stage-2 PTE is installed

On Fri, Jul 26, 2024 at 04:52:05PM GMT, Sean Christopherson wrote:
> Don't mark pages dirty if KVM bails from the page fault handler without
> installing a stage-2 mapping, i.e. if the page is guaranteed to not be
> written by the guest.
> 
> In addition to being a (very) minor fix, this paves the way for converting
> RISC-V to use kvm_release_faultin_page().
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/riscv/kvm/mmu.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index b63650f9b966..06aa5a0d056d 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -669,7 +669,6 @@ int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu,
>  		goto out_unlock;
>  
>  	if (writable) {
> -		kvm_set_pfn_dirty(hfn);
>  		mark_page_dirty(kvm, gfn);
>  		ret = gstage_map_page(kvm, pcache, gpa, hfn << PAGE_SHIFT,
>  				      vma_pagesize, false, true);
> @@ -682,6 +681,9 @@ int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu,
>  		kvm_err("Failed to map in G-stage\n");
>  
>  out_unlock:
> +	if ((!ret || ret == -EEXIST) && writable)
> +		kvm_set_pfn_dirty(hfn);
> +
>  	spin_unlock(&kvm->mmu_lock);
>  	kvm_set_pfn_accessed(hfn);
>  	kvm_release_pfn_clean(hfn);
> -- 
> 2.46.0.rc1.232.g9752f9e123-goog
>

Reviewed-by: Andrew Jones <ajones@...tanamicro.com>