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From: Paolo Bonzini <pbonzini@redhat.com>
To: Bandan Das <bsd@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, david@redhat.com
Subject: Re: [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits
Date: Tue, 11 Apr 2017 19:54:29 -0400 (EDT)	[thread overview]
Message-ID: <317734077.12913155.1491954869446.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <jpgefwyldqj.fsf@linux.bootlegged.copy>



----- Original Message -----
> From: "Bandan Das" <bsd@redhat.com>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, david@redhat.com
> Sent: Wednesday, April 12, 2017 7:35:16 AM
> Subject: Re: [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits
> 
> Paolo Bonzini <pbonzini@redhat.com> writes:
> ...
> >  	accessed_dirty = have_ad ? PT_GUEST_ACCESSED_MASK : 0;
> > +
> > +	/*
> > +	 * FIXME: on Intel processors, loads of the PDPTE registers for PAE
> > paging
> > +	 * by the MOV to CR instruction are treated as reads and do not cause the
> > +	 * processor to set the dirty flag in tany EPT paging-structure entry.
> > +	 */
> 
> Minor typo: "in any EPT paging-structure entry".
> 
> > +	nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK;
> > +
> >  	pt_access = pte_access = ACC_ALL;
> >  	++walker->level;
> >  
> > @@ -338,7 +337,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker
> > *walker,
> >  		walker->pte_gpa[walker->level - 1] = pte_gpa;
> >  
> >  		real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
> > -					      PFERR_USER_MASK|PFERR_WRITE_MASK,
> > +					      nested_access,
> >  					      &walker->fault);
> 
> I can't seem to understand the significance of this change (or for that
> matter what was before this change).
> 
> mmu->translate_gpa() just returns gfn_to_gpa(table_gfn), right ?

For EPT it is, you're right it's fishy.  The "nested_access" should be
computed in translate_nested_gpa, which is where kvm->arch.nested_mmu
(non-EPT) requests to access kvm->arch.mmu (EPT).

In practice we need to define a new function
vcpu->arch.mmu.gva_to_gpa_nested that computes the nested_access
and calls cpu->arch.mmu.gva_to_gpa.

Thanks,

Paolo

  reply	other threads:[~2017-04-11 23:54 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-30  9:55 [PATCH v2 0/6] KVM: nVMX: nested EPT improvements and A/D bits, RDRAND and RDSEED exits Paolo Bonzini
2017-03-30  9:55 ` [PATCH 1/6] KVM: nVMX: we support 1GB EPT pages Paolo Bonzini
2017-03-30  9:55 ` [PATCH 2/6] KVM: VMX: remove bogus check for invalid EPT violation Paolo Bonzini
2017-03-30 16:30   ` Jim Mattson
2017-04-03 11:17   ` David Hildenbrand
2017-04-12 20:00   ` David Hildenbrand
2017-03-30  9:55 ` [PATCH 3/6] kvm: x86: MMU support for EPT accessed/dirty bits Paolo Bonzini
2017-03-31 13:52   ` Radim Krčmář
2017-03-30  9:55 ` [PATCH 4/6] kvm: nVMX: support " Paolo Bonzini
2017-03-31 16:24   ` Radim Krčmář
2017-03-31 16:26     ` Paolo Bonzini
2017-04-11 23:35   ` Bandan Das
2017-04-11 23:54     ` Paolo Bonzini [this message]
2017-04-12 23:02       ` Bandan Das
2017-04-14  5:17         ` Paolo Bonzini
2017-03-30  9:55 ` [PATCH 5/6] KVM: VMX: add missing exit reasons Paolo Bonzini
2017-03-30  9:55 ` [PATCH 6/6] KVM: nVMX: support RDRAND and RDSEED exiting Paolo Bonzini
2017-03-30 16:54   ` Jim Mattson
2017-03-31 11:13 ` [PATCH v2 0/6] KVM: nVMX: nested EPT improvements and A/D bits, RDRAND and RDSEED exits Paolo Bonzini
  -- strict thread matches above, loose matches on Subject: below --
2017-03-08 18:03 [PATCH " Paolo Bonzini
2017-03-08 18:03 ` [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits Paolo Bonzini

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