From: Alex Williamson <alex.williamson@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: kvm <kvm@vger.kernel.org>, Avi Kivity <avi@redhat.com>
Subject: Re: KVM: MMU: only write protect mappings at pagetable level
Date: Wed, 22 Dec 2010 10:48:56 -0700 [thread overview]
Message-ID: <1293040136.2928.0.camel@x201> (raw)
In-Reply-To: <20101222110157.GA4266@amt.cnet>
On Wed, 2010-12-22 at 09:01 -0200, Marcelo Tosatti wrote:
> If a pagetable contains a writeable large spte, all of its sptes will be
> write protected, including non-leaf ones, leading to endless pagefaults.
>
> Do not write protect pages above PT_PAGE_TABLE_LEVEL, as the spte fault
> paths assume non-leaf sptes are writable.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index c3853d5..c716ff8 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3442,6 +3442,9 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
> if (!test_bit(slot, sp->slot_bitmap))
> continue;
>
> + if (sp->role.level != PT_PAGE_TABLE_LEVEL)
> + continue;
> +
> pt = sp->spt;
> for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
> /* avoid RMW */
Works for me.
Tested-by: Alex Williamson <alex.williamson@redhat.com>
prev parent reply other threads:[~2010-12-22 17:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-22 11:01 KVM: MMU: only write protect mappings at pagetable level Marcelo Tosatti
2010-12-22 11:07 ` Avi Kivity
2010-12-22 11:12 ` Marcelo Tosatti
2010-12-22 13:01 ` Avi Kivity
2010-12-22 13:06 ` Marcelo Tosatti
2010-12-22 14:06 ` Avi Kivity
2010-12-22 17:48 ` Alex Williamson [this message]
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