From: Avi Kivity <avi@redhat.com>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH 4/4] KVM: MMU: Don't touch unsync sp in kvm_mmu_pte_write()
Date: Mon, 20 Sep 2010 17:24:47 +0200 [thread overview]
Message-ID: <4C977CBF.6030702@redhat.com> (raw)
In-Reply-To: <4C976DF6.1020905@cn.fujitsu.com>
On 09/20/2010 04:21 PM, Xiao Guangrong wrote:
> Gfn may have many shadow pages, when one sp need be synced, we write
> protected sp->gfn and sync this sp but we keep other shadow pages
> asynchronous
>
> So, while gfn happen page fault, let it not touches unsync page, the unsync
> page only updated at invlpg/flush TLB time
>
> @@ -3157,6 +3164,9 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>
> mask.cr0_wp = mask.cr4_pae = mask.nxe = 1;
> for_each_gfn_indirect_valid_sp(vcpu->kvm, sp, gfn, node) {
> + if (sp->unsync)
> + continue;
> +
>
Not sure this is a win. If a gpte is updated from having p=0 to p=1 (or
permissions upgraded), we may not have an invlpg to sync the spte, since
the hardware doesn't require it. With this change, we may get an extra #PF.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2010-09-20 15:24 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-20 14:18 [PATCH 1/4] KVM: MMU: rename 'sp->root_count' to 'sp->active_count' Xiao Guangrong
2010-09-20 14:19 ` [PATCH 2/4] KVM: MMU: support unsync sp out of the protection of 'mmu_lock' Xiao Guangrong
2010-09-20 15:19 ` Avi Kivity
2010-09-23 3:05 ` Xiao Guangrong
2010-09-26 13:02 ` Avi Kivity
2010-09-20 14:20 ` [PATCH 3/4] KVM: MMU: move reserved bits check to FNAME(update_pte) Xiao Guangrong
2010-09-20 14:21 ` [PATCH 4/4] KVM: MMU: Don't touch unsync sp in kvm_mmu_pte_write() Xiao Guangrong
2010-09-20 15:24 ` Avi Kivity [this message]
2010-09-23 2:59 ` Xiao Guangrong
2010-09-26 13:09 ` Avi Kivity
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