From: Marcelo Tosatti <mtosatti@redhat.com>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH 1/4] KVM: MMU: don't drop spte if overwrite it from W to RO
Date: Tue, 16 Nov 2010 18:24:15 -0200 [thread overview]
Message-ID: <20101116202414.GA24156@amt.cnet> (raw)
In-Reply-To: <4CDD173E.8010706@cn.fujitsu.com>
On Fri, Nov 12, 2010 at 06:30:22PM +0800, Xiao Guangrong wrote:
> We just need flush tlb if overwrite a writable spte with a read-only one
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> ---
> arch/x86/kvm/mmu.c | 19 +++++++++----------
> 1 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 4b6d54c..1a93ab4 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2044,6 +2044,15 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> if (pte_access & ACC_WRITE_MASK)
> mark_page_dirty(vcpu->kvm, gfn);
>
> + /*
> + * If we overwrite a writable spte with a read-only one,
> + * flush remote TLBs. Otherwise rmap_write_protect will
> + * find a read-only spte, even though the writable spte
> + * might be cached on a CPU's TLB.
> + */
> + else if (is_writable_pte(*sptep))
> + ret = 1;
> +
The return value of set_spte indicates whether the gfn being mapped to
was write protected, not if a TLB flush is necessary.
> set_pte:
> update_spte(sptep, spte);
> done:
> @@ -2084,16 +2093,6 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> spte_to_pfn(*sptep), pfn);
> drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);
> kvm_flush_remote_tlbs(vcpu->kvm);
> - /*
> - * If we overwrite a writable spte with a read-only one,
> - * drop it and flush remote TLBs. Otherwise rmap_write_protect
> - * will find a read-only spte, even though the writable spte
> - * might be cached on a CPU's TLB.
> - */
> - } else if (is_writable_pte(*sptep) &&
> - (!(pte_access & ACC_WRITE_MASK) || !dirty)) {
> - drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);
> - kvm_flush_remote_tlbs(vcpu->kvm);
> } else
> was_rmapped = 1;
And here, flush will only happen if overwrite is RW->RO.
next prev parent reply other threads:[~2010-11-16 20:29 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-12 10:30 [PATCH 1/4] KVM: MMU: don't drop spte if overwrite it from W to RO Xiao Guangrong
2010-11-12 10:33 ` [PATCH 2/4] KVM: MMU: rename 'reset_host_protection' to 'host_writeable' Xiao Guangrong
2010-11-12 10:37 ` Xiao Guangrong
2010-11-12 10:34 ` [PATCH 3/4] KVM: MMU: notrap it if gpte's reserved is set Xiao Guangrong
2010-11-14 10:56 ` Avi Kivity
2010-11-15 5:41 ` Xiao Guangrong
2010-11-15 9:17 ` Avi Kivity
2010-11-17 1:45 ` Xiao Guangrong
2010-11-12 10:35 ` [PATCH 4/4] KVM: MMU: cleanup update_pte, pte_prefetch and sync_page functions Xiao Guangrong
2010-11-16 20:52 ` Marcelo Tosatti
2010-11-17 1:58 ` Xiao Guangrong
2010-11-14 10:52 ` [PATCH 1/4] KVM: MMU: don't drop spte if overwrite it from W to RO Avi Kivity
2010-11-15 5:34 ` Xiao Guangrong
2010-11-16 20:24 ` Marcelo Tosatti [this message]
2010-11-17 1:42 ` Xiao Guangrong
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