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

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

[Yu Zhang]

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 <yu.c.zhang@linux.intel.com>
---
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
---
 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

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

[Yu Zhang]

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 <yu.c.zhang@linux.intel.com>
> ---
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: linux-kernel@vger.kernel.org
> ---
>  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

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

[Vitaly Kuznetsov]

Yu Zhang <yu.c.zhang@linux.intel.com> 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 <yu.c.zhang@linux.intel.com>
> ---
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: linux-kernel@vger.kernel.org
> ---
>  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 <vkuznets@redhat.com>

-- 
Vitaly

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

[Yu Zhang]

On Wed, Feb 20, 2019 at 03:06:10PM +0100, Vitaly Kuznetsov wrote:
> Yu Zhang <yu.c.zhang@linux.intel.com> 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 <yu.c.zhang@linux.intel.com>
> > ---
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: linux-kernel@vger.kernel.org
> > ---
> >  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 <vkuznets@redhat.com>
> 
> -- 
> Vitaly
> 

B.R.
Yu

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

[Paolo Bonzini]

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 <yu.c.zhang@linux.intel.com>
>> ---
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: linux-kernel@vger.kernel.org
>> ---
>>  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
>