Messages in this thread | | | Subject | Re: [PATCH 2/7] KVM: X86: Synchronize the shadow pagetable before link it | From | Lai Jiangshan <> | Date | Fri, 3 Sep 2021 08:44:53 +0800 |
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On 2021/9/3 07:54, Sean Christopherson wrote: > > trace_get_page: > diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h > index 50ade6450ace..5b13918a55c2 100644 > --- a/arch/x86/kvm/mmu/paging_tmpl.h > +++ b/arch/x86/kvm/mmu/paging_tmpl.h > @@ -704,6 +704,10 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, > access = gw->pt_access[it.level - 2]; > sp = kvm_mmu_get_page(vcpu, table_gfn, fault->addr, > it.level-1, false, access); > + if (sp->unsync_children) { > + kvm_make_all_cpus_request(KVM_REQ_MMU_SYNC, vcpu); > + return RET_PF_RETRY;
Making KVM_REQ_MMU_SYNC be able remotely is good idea. But if the sp is not linked, the @sp might not be synced even we tried many times. So we should continue to link it.
But if we continue to link it, KVM_REQ_MMU_SYNC should be extended to sync all roots (current root and prev_roots). And maybe add a KVM_REQ_MMU_SYNC_CURRENT for current root syncing.
It is not going to be a simple. I have a new way to sync pages and also fix the problem, but that include several non-fix patches.
We need to fix this problem in the simplest way. In my patch mmu_sync_children() has a @root argument. I think we can disallow releasing the lock when @root is false. Is it OK?
> + } > } > > /* > -- >
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