On Tue, Jan 06, 2009 at 04:29:59PM +0200, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> On Tue, Jan 06, 2009 at 12:41:40PM +0200, Avi Kivity wrote:
>>
>>> Alexander Graf wrote:
>>>
>>>> Avi Kivity wrote:
>>>>
>>>>> From: Avi Kivity <[email protected]>
>>>>>
>>>>> Don't allow a vcpu with cr4.pge cleared to use a shadow page created with
>>>>> cr4.pge set; this might cause a cr3 switch not to sync ptes that have the
>>>>> global bit set (the global bit has no effect if !cr4.pge).
>>>>>
>>>>> This can only occur on smp with different cr4.pge settings for different
>>>>> vcpus (since a cr4 change will resync the shadow ptes), but there's no
>>>>> cost to being correct here.
>>>>>
>>>>> Signed-off-by: Avi Kivity <[email protected]>
>>>>>
>>>>> diff --git a/arch/x86/include/asm/kvm_host.h
>>>>> b/arch/x86/include/asm/kvm_host.h
>>>>> index f49bfd0..ab8ef1d 100644
>>>>> --- a/arch/x86/include/asm/kvm_host.h
>>>>> +++ b/arch/x86/include/asm/kvm_host.h
>>>>> @@ -183,6 +183,7 @@ union kvm_mmu_page_role {
>>>>> unsigned metaphysical:1;
>>>>> unsigned access:3;
>>>>> unsigned invalid:1;
>>>>> + unsigned cr4_pge:1;
>>>>> };
>>>>> };
>>>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>>>> index c4da7fb..aa4575c 100644
>>>>> --- a/arch/x86/kvm/x86.c
>>>>> +++ b/arch/x86/kvm/x86.c
>>>>> @@ -363,6 +363,7 @@ void kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long
>>>>> cr4)
>>>>> }
>>>>> kvm_x86_ops->set_cr4(vcpu, cr4);
>>>>> vcpu->arch.cr4 = cr4;
>>>>> + vcpu->arch.mmu.base_role.cr4_pge = !!(cr4 & X86_CR4_PGE);
>>>>>
>>>> This line broke VMware ESX bootup using NPT on one VCPU for me. If I
>>>> comment it out and apply my patches to actually make ESX run, it boots
>>>> again.
>>>>
>>> I think this might be the problem:
>>>
>>>
>>>> static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
>>>> bool can_unsync)
>>>> {
>>>> struct kvm_mmu_page *shadow;
>>>>
>>>> shadow = kvm_mmu_lookup_page(vcpu->kvm, gfn);
>>>> if (shadow) {
>>>> if (shadow->role.level != PT_PAGE_TABLE_LEVEL)
>>>> return 1;
>>>> if (shadow->unsync)
>>>> return 0;
>>>> if (can_unsync && oos_shadow)
>>>> return kvm_unsync_page(vcpu, shadow);
>>>> return 1;
>>>> }
>>>> return 0;
>>>> }
>>>>
>>>>
>>> lookup_page() is not deterministic if there are multiple shadows for
>>> a page, and the patch increases multiple shadows.
>>>
>>> Marcelo, shouldn't there be a for_each in there?
>>>
>>
>> static int kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) {
>>
>> unsigned index;
>> struct hlist_head *bucket;
>> struct kvm_mmu_page *s;
>> struct hlist_node *node, *n;
>>
>> index = kvm_page_table_hashfn(sp->gfn);
>> bucket = &vcpu->kvm->arch.mmu_page_hash[index];
>> /* don't unsync if pagetable is shadowed with multiple roles */
>> hlist_for_each_entry_safe(s, node, n, bucket, hash_link) {
>> if (s->gfn != sp->gfn || s->role.metaphysical)
>> continue;
>> if (s->role.word != sp->role.word)
>> return 1;
>> }
>>
>> This one?
>>
>
> Yes...
>
> Looks like kvm_unsync_page can be folded into mmu_need_write_protect
> (after which we can drop lookup_page(), which is not a good API). But
> that's after we solve the current problem.
>
> Looks like the addition of a second role for non-pge mode confuses the
> mmu. After the second page is created, mmu_need_write_protect() will
> return 1, but previously existing sptes can still be writable?
>
> Looks like we need to call rmap_write_protect() when the new page is
> created.
kvm_mmu_get_page:
hlist_for_each_entry_safe(sp, node, tmp, bucket, hash_link)
if (sp->gfn == gfn) {
if (sp->unsync)
if (kvm_sync_page(vcpu, sp))
continue;
So rmap_write_protect is called when the new page is created. Looking
at it now.
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