| Message ID | 20190910102742.47729-3-xiaoyao.li@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: CPUID: emulation flow adjustment and one minor refinement when updating maxphyaddr | expand |
On Tue, Sep 10, 2019 at 3:42 AM Xiaoyao Li <xiaoyao.li@intel.com> wrote: > > Since both of maxphyaddr updating and virtual address width checking > need to query the cpuid leaf 0x80000008. We can put them together. > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> > --- > arch/x86/kvm/cpuid.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 67fa44ab87af..fd0a66079001 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -118,6 +118,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > best->ebx = xstate_required_size(vcpu->arch.xcr0, true); > > /* > + * Update physical address width and check virtual address width. > * The existing code assumes virtual address is 48-bit or 57-bit in the > * canonical address checks; exit if it is ever changed. > */ > @@ -127,7 +128,10 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0) > return -EINVAL; > + > + vcpu->arch.maxphyaddr = best->eax & 0xff; > } > + vcpu->arch.maxphyaddr = 36; Perhaps I'm missing something, but it looks to me like you always set vcpu->arch.maxphyaddr to 36, regardless of what may be enumerated by leaf 0x80000008. Is there really much of an advantage to open-coding cpuid_query_maxphyaddr() here? > best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0); > if (kvm_hlt_in_guest(vcpu->kvm) && best && > @@ -144,8 +148,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > } > } > > - /* Update physical-address width */ > - vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); > kvm_mmu_reset_context(vcpu); > > kvm_pmu_refresh(vcpu); > -- > 2.19.1 >
On Tue, 2019-09-10 at 10:13 -0700, Jim Mattson wrote: > On Tue, Sep 10, 2019 at 3:42 AM Xiaoyao Li <xiaoyao.li@intel.com> wrote: > > > > Since both of maxphyaddr updating and virtual address width checking > > need to query the cpuid leaf 0x80000008. We can put them together. > > > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> > > --- > > arch/x86/kvm/cpuid.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > > index 67fa44ab87af..fd0a66079001 100644 > > --- a/arch/x86/kvm/cpuid.c > > +++ b/arch/x86/kvm/cpuid.c > > @@ -118,6 +118,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > best->ebx = xstate_required_size(vcpu->arch.xcr0, true); > > > > /* > > + * Update physical address width and check virtual address width. > > * The existing code assumes virtual address is 48-bit or 57-bit in > > the > > * canonical address checks; exit if it is ever changed. > > */ > > @@ -127,7 +128,10 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > > > if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0) > > return -EINVAL; > > + > > + vcpu->arch.maxphyaddr = best->eax & 0xff; > > } > > + vcpu->arch.maxphyaddr = 36; > > Perhaps I'm missing something, but it looks to me like you always set > vcpu->arch.maxphyaddr to 36, regardless of what may be enumerated by > leaf 0x80000008. Oh, I made a stupid mistake. It should be included in the else case. > > Is there really much of an advantage to open-coding > cpuid_query_maxphyaddr() here? Indeed not so much. It can avoid two more kvm_find_cpuid_entry() calling that we don't handle leaf 0x80000008 twice in two place. > > best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0); > > if (kvm_hlt_in_guest(vcpu->kvm) && best && > > @@ -144,8 +148,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > } > > } > > > > - /* Update physical-address width */ > > - vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); > > kvm_mmu_reset_context(vcpu); > > > > kvm_pmu_refresh(vcpu); > > -- > > 2.19.1 > >
On Tue, Sep 10, 2019 at 3:52 PM Xiaoyao Li <xiaoyao.li@intel.com> wrote: > > On Tue, 2019-09-10 at 10:13 -0700, Jim Mattson wrote: > > On Tue, Sep 10, 2019 at 3:42 AM Xiaoyao Li <xiaoyao.li@intel.com> wrote: > > > > > > Since both of maxphyaddr updating and virtual address width checking > > > need to query the cpuid leaf 0x80000008. We can put them together. > > > > > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> > > > --- > > > arch/x86/kvm/cpuid.c | 6 ++++-- > > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > > > index 67fa44ab87af..fd0a66079001 100644 > > > --- a/arch/x86/kvm/cpuid.c > > > +++ b/arch/x86/kvm/cpuid.c > > > @@ -118,6 +118,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > > best->ebx = xstate_required_size(vcpu->arch.xcr0, true); > > > > > > /* > > > + * Update physical address width and check virtual address width. > > > * The existing code assumes virtual address is 48-bit or 57-bit in > > > the > > > * canonical address checks; exit if it is ever changed. > > > */ > > > @@ -127,7 +128,10 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > > > > > if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0) > > > return -EINVAL; > > > + > > > + vcpu->arch.maxphyaddr = best->eax & 0xff; > > > } > > > + vcpu->arch.maxphyaddr = 36; > > > > Perhaps I'm missing something, but it looks to me like you always set > > vcpu->arch.maxphyaddr to 36, regardless of what may be enumerated by > > leaf 0x80000008. > > Oh, I made a stupid mistake. It should be included in the else case. > > > > > Is there really much of an advantage to open-coding > > cpuid_query_maxphyaddr() here? > > Indeed not so much. > It can avoid two more kvm_find_cpuid_entry() calling that we don't handle leaf > 0x80000008 twice in two place. I'm inclined to leave things as they are. As your previous attempt demonstrates, having the same logic replicated in multiple places is prone to error. I can't imagine that this would be a performance-sensitive path. > > > best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0); > > > if (kvm_hlt_in_guest(vcpu->kvm) && best && > > > @@ -144,8 +148,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) > > > } > > > } > > > > > > - /* Update physical-address width */ > > > - vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); > > > kvm_mmu_reset_context(vcpu); > > > > > > kvm_pmu_refresh(vcpu); > > > -- > > > 2.19.1 > > > >
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 67fa44ab87af..fd0a66079001 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -118,6 +118,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) best->ebx = xstate_required_size(vcpu->arch.xcr0, true); /* + * Update physical address width and check virtual address width. * The existing code assumes virtual address is 48-bit or 57-bit in the * canonical address checks; exit if it is ever changed. */ @@ -127,7 +128,10 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) if (vaddr_bits != 48 && vaddr_bits != 57 && vaddr_bits != 0) return -EINVAL; + + vcpu->arch.maxphyaddr = best->eax & 0xff; } + vcpu->arch.maxphyaddr = 36; best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0); if (kvm_hlt_in_guest(vcpu->kvm) && best && @@ -144,8 +148,6 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) } } - /* Update physical-address width */ - vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); kvm_mmu_reset_context(vcpu); kvm_pmu_refresh(vcpu);
Since both of maxphyaddr updating and virtual address width checking need to query the cpuid leaf 0x80000008. We can put them together. Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> --- arch/x86/kvm/cpuid.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)