2019-01-31 16:14:11

by Yu Zhang

Subject: [PATCH] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

Previously, commit 7dcd57552008 ("x86/kvm/mmu: check if tdp/shadow
MMU reconfiguration is needed") offered some optimization to avoid
the unnecessary reconfiguration. Yet one scenario is broken - when
cpuid changes VM's maximum physical address width, reconfiguration
is needed to reset the reserved bits. Also, the TDP may need to
reset its shadow_root_level when this value is changed.

To fix this, a new field, maxphyaddr, is introduced in the extended
role structure to keep track of the configured guest physical address
width.

Signed-off-by: Yu Zhang <[email protected]>
---
Cc: Paolo Bonzini <[email protected]>
Cc: "Radim Krčmář" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu.c | 1 +
2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4660ce9..be87f71 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -299,6 +299,7 @@ struct kvm_mmu_memory_cache {
unsigned int cr4_smap:1;
unsigned int cr4_smep:1;
unsigned int cr4_la57:1;
+ unsigned int maxphyaddr:6;
};
};

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ce770b4..2b74505 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4769,6 +4769,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
ext.cr4_pse = !!is_pse(vcpu);
ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
+ ext.maxphyaddr = cpuid_maxphyaddr(vcpu);

ext.valid = 1;

--
1.9.1

2019-02-20 07:11:42

by Yu Zhang

Subject: Re: [PATCH] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

Hi Paolo, any comments on this patch? And the other one(kvm: x86: Return
LA57 feature based on hardware capability )? :-)

On Fri, Feb 01, 2019 at 12:09:23AM +0800, Yu Zhang wrote:
> Previously, commit 7dcd57552008 ("x86/kvm/mmu: check if tdp/shadow
> MMU reconfiguration is needed") offered some optimization to avoid
> the unnecessary reconfiguration. Yet one scenario is broken - when
> cpuid changes VM's maximum physical address width, reconfiguration
> is needed to reset the reserved bits. Also, the TDP may need to
> reset its shadow_root_level when this value is changed.
>
> To fix this, a new field, maxphyaddr, is introduced in the extended
> role structure to keep track of the configured guest physical address
> width.
>
> Signed-off-by: Yu Zhang <[email protected]>
> ---
> Cc: Paolo Bonzini <[email protected]>
> Cc: "Radim Krčmář" <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: [email protected]
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/mmu.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 4660ce9..be87f71 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -299,6 +299,7 @@ struct kvm_mmu_memory_cache {
> unsigned int cr4_smap:1;
> unsigned int cr4_smep:1;
> unsigned int cr4_la57:1;
> + unsigned int maxphyaddr:6;
> };
> };
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ce770b4..2b74505 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4769,6 +4769,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
> ext.cr4_pse = !!is_pse(vcpu);
> ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
> ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
> + ext.maxphyaddr = cpuid_maxphyaddr(vcpu);
>
> ext.valid = 1;
>
> --
> 1.9.1
>

Thanks
Yu

2019-02-20 14:07:18

by Vitaly Kuznetsov

Subject: Re: [PATCH] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

Yu Zhang <[email protected]> writes:

> Previously, commit 7dcd57552008 ("x86/kvm/mmu: check if tdp/shadow
> MMU reconfiguration is needed") offered some optimization to avoid
> the unnecessary reconfiguration. Yet one scenario is broken - when
> cpuid changes VM's maximum physical address width, reconfiguration
> is needed to reset the reserved bits. Also, the TDP may need to
> reset its shadow_root_level when this value is changed.
>
> To fix this, a new field, maxphyaddr, is introduced in the extended
> role structure to keep track of the configured guest physical address
> width.
>
> Signed-off-by: Yu Zhang <[email protected]>
> ---
> Cc: Paolo Bonzini <[email protected]>
> Cc: "Radim Krčmář" <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: [email protected]
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/mmu.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 4660ce9..be87f71 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -299,6 +299,7 @@ struct kvm_mmu_memory_cache {
> unsigned int cr4_smap:1;
> unsigned int cr4_smep:1;
> unsigned int cr4_la57:1;
> + unsigned int maxphyaddr:6;
> };
> };
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ce770b4..2b74505 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4769,6 +4769,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
> ext.cr4_pse = !!is_pse(vcpu);
> ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
> ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
> + ext.maxphyaddr = cpuid_maxphyaddr(vcpu);
>
> ext.valid = 1;

It seems that we can now drop 'valid' from role_ext as maxphyaddr can't
be 0.

Reviewed-by: Vitaly Kuznetsov <[email protected]>

--
Vitaly

2019-02-21 07:06:59

by Yu Zhang

Subject: Re: [PATCH] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

On Wed, Feb 20, 2019 at 03:06:10PM +0100, Vitaly Kuznetsov wrote:
> Yu Zhang <[email protected]> writes:
>
> > Previously, commit 7dcd57552008 ("x86/kvm/mmu: check if tdp/shadow
> > MMU reconfiguration is needed") offered some optimization to avoid
> > the unnecessary reconfiguration. Yet one scenario is broken - when
> > cpuid changes VM's maximum physical address width, reconfiguration
> > is needed to reset the reserved bits. Also, the TDP may need to
> > reset its shadow_root_level when this value is changed.
> >
> > To fix this, a new field, maxphyaddr, is introduced in the extended
> > role structure to keep track of the configured guest physical address
> > width.
> >
> > Signed-off-by: Yu Zhang <[email protected]>
> > ---
> > Cc: Paolo Bonzini <[email protected]>
> > Cc: "Radim Krčmář" <[email protected]>
> > Cc: Thomas Gleixner <[email protected]>
> > Cc: Ingo Molnar <[email protected]>
> > Cc: Borislav Petkov <[email protected]>
> > Cc: "H. Peter Anvin" <[email protected]>
> > Cc: [email protected]
> > ---
> > arch/x86/include/asm/kvm_host.h | 1 +
> > arch/x86/kvm/mmu.c | 1 +
> > 2 files changed, 2 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 4660ce9..be87f71 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -299,6 +299,7 @@ struct kvm_mmu_memory_cache {
> > unsigned int cr4_smap:1;
> > unsigned int cr4_smep:1;
> > unsigned int cr4_la57:1;
> > + unsigned int maxphyaddr:6;
> > };
> > };
> >
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index ce770b4..2b74505 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -4769,6 +4769,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
> > ext.cr4_pse = !!is_pse(vcpu);
> > ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
> > ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
> > + ext.maxphyaddr = cpuid_maxphyaddr(vcpu);
> >
> > ext.valid = 1;
>
> It seems that we can now drop 'valid' from role_ext as maxphyaddr can't
> be 0.

Thanks, Vitaly. Yes, we can drop this field. :)

>
> Reviewed-by: Vitaly Kuznetsov <[email protected]>
>
> --
> Vitaly
>

B.R.
Yu

2019-02-22 18:25:10

by Paolo Bonzini

Subject: Re: [PATCH] KVM: MMU: record maximum physical address width in kvm_mmu_extended_role

On 20/02/19 08:06, Yu Zhang wrote:
> Hi Paolo, any comments on this patch? And the other one(kvm: x86: Return
> LA57 feature based on hardware capability )? :-)

Queued both, thanks.

Paolo

> On Fri, Feb 01, 2019 at 12:09:23AM +0800, Yu Zhang wrote:
>> Previously, commit 7dcd57552008 ("x86/kvm/mmu: check if tdp/shadow
>> MMU reconfiguration is needed") offered some optimization to avoid
>> the unnecessary reconfiguration. Yet one scenario is broken - when
>> cpuid changes VM's maximum physical address width, reconfiguration
>> is needed to reset the reserved bits. Also, the TDP may need to
>> reset its shadow_root_level when this value is changed.
>>
>> To fix this, a new field, maxphyaddr, is introduced in the extended
>> role structure to keep track of the configured guest physical address
>> width.
>>
>> Signed-off-by: Yu Zhang <[email protected]>
>> ---
>> Cc: Paolo Bonzini <[email protected]>
>> Cc: "Radim Krčmář" <[email protected]>
>> Cc: Thomas Gleixner <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: Borislav Petkov <[email protected]>
>> Cc: "H. Peter Anvin" <[email protected]>
>> Cc: [email protected]
>> ---
>> arch/x86/include/asm/kvm_host.h | 1 +
>> arch/x86/kvm/mmu.c | 1 +
>> 2 files changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 4660ce9..be87f71 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -299,6 +299,7 @@ struct kvm_mmu_memory_cache {
>> unsigned int cr4_smap:1;
>> unsigned int cr4_smep:1;
>> unsigned int cr4_la57:1;
>> + unsigned int maxphyaddr:6;
>> };
>> };
>>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index ce770b4..2b74505 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -4769,6 +4769,7 @@ static union kvm_mmu_extended_role kvm_calc_mmu_role_ext(struct kvm_vcpu *vcpu)
>> ext.cr4_pse = !!is_pse(vcpu);
>> ext.cr4_pke = !!kvm_read_cr4_bits(vcpu, X86_CR4_PKE);
>> ext.cr4_la57 = !!kvm_read_cr4_bits(vcpu, X86_CR4_LA57);
>> + ext.maxphyaddr = cpuid_maxphyaddr(vcpu);
>>
>> ext.valid = 1;
>>
>> --
>> 1.9.1
>>
>
> Thanks
> Yu
>