linux-kernel - Re: [PATCH V2 02/10] KVM: X86: Synchronize the shadow pagetable before link it

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Message-ID: <40f67a70-5076-3806-1ec7-a4ac50d13774@redhat.com>
Date:   Thu, 23 Sep 2021 16:36:24 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     Lai Jiangshan <laijs@...ux.alibaba.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH V2 02/10] KVM: X86: Synchronize the shadow pagetable
 before link it

On 18/09/21 02:56, Lai Jiangshan wrote:
> +			 * It also makes KVM_REQ_MMU_SYNC request if the @sp
> +			 * is linked on a different addr to expedite it.
> +			 */
> +			if (sp->unsync_children &&
> +			    mmu_sync_children(vcpu, sp, false)) {
> +				kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
> +				return RET_PF_RETRY;
> +			}
>   		}

I think we can put the sync in mmu_sync_children:

-			if (!can_yield)
+			if (!can_yield) {
+				/*
+				 * Some progress has been made so the caller
+				 * can simply retry, but we can expedite the
+				 * process by forcing a sync to happen.
+				 */
+				kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
  				return -EINTR;
+			}

Paolo