| Message ID | 20210919024246.89230-2-jiangshanlai@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: X86: Don't reset mmu context when changing PGE or PCID | expand |
On Sun, Sep 19, 2021, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@linux.alibaba.com> > > X86_CR4_PCIDE doesn't participate in kvm_mmu_role, so the mmu context > doesn't need to be reset. It is only required to flush all the guest > tlb. > > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > --- > arch/x86/kvm/x86.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 86539c1686fa..7494ea0e7922 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -116,6 +116,7 @@ static void enter_smm(struct kvm_vcpu *vcpu); > static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags); > static void store_regs(struct kvm_vcpu *vcpu); > static int sync_regs(struct kvm_vcpu *vcpu); > +static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu); > > static int __set_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); > static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); > @@ -1042,9 +1043,10 @@ EXPORT_SYMBOL_GPL(kvm_is_valid_cr4); > > void kvm_post_set_cr4(struct kvm_vcpu *vcpu, unsigned long old_cr4, unsigned long cr4) > { > - if (((cr4 ^ old_cr4) & KVM_MMU_CR4_ROLE_BITS) || > - (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE))) > + if ((cr4 ^ old_cr4) & KVM_MMU_CR4_ROLE_BITS) > kvm_mmu_reset_context(vcpu); > + else if (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE)) > + kvm_vcpu_flush_tlb_guest(vcpu); Unless there's a corner case I'm missing, I would prefer this to use kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu) instead of calling kvm_vcpu_flush_tlb_guest() directly. The odds of flushes actually being batched is low, it's more to document that kvm_post_set_cr4() _isn't_ special.
On Thu, Oct 14, 2021, Sean Christopherson wrote: > On Sun, Sep 19, 2021, Lai Jiangshan wrote: > > From: Lai Jiangshan <laijs@linux.alibaba.com> > > > > X86_CR4_PCIDE doesn't participate in kvm_mmu_role, so the mmu context > > doesn't need to be reset. It is only required to flush all the guest > > tlb. > > > > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > > --- > > arch/x86/kvm/x86.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 86539c1686fa..7494ea0e7922 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -116,6 +116,7 @@ static void enter_smm(struct kvm_vcpu *vcpu); > > static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags); > > static void store_regs(struct kvm_vcpu *vcpu); > > static int sync_regs(struct kvm_vcpu *vcpu); > > +static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu); > > > > static int __set_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); > > static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); > > @@ -1042,9 +1043,10 @@ EXPORT_SYMBOL_GPL(kvm_is_valid_cr4); > > > > void kvm_post_set_cr4(struct kvm_vcpu *vcpu, unsigned long old_cr4, unsigned long cr4) > > { > > - if (((cr4 ^ old_cr4) & KVM_MMU_CR4_ROLE_BITS) || > > - (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE))) > > + if ((cr4 ^ old_cr4) & KVM_MMU_CR4_ROLE_BITS) > > kvm_mmu_reset_context(vcpu); > > + else if (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE)) > > + kvm_vcpu_flush_tlb_guest(vcpu); > > Unless there's a corner case I'm missing, I would prefer this to use > kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu) instead of calling > kvm_vcpu_flush_tlb_guest() directly. The odds of flushes actually being batched > is low, it's more to document that kvm_post_set_cr4() _isn't_ special. Forgot to say, with the change to KVM_REQ_TLB_FLUSH_GUEST: Reviewed-by: Sean Christopherson <seanjc@google.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 86539c1686fa..7494ea0e7922 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -116,6 +116,7 @@ static void enter_smm(struct kvm_vcpu *vcpu); static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags); static void store_regs(struct kvm_vcpu *vcpu); static int sync_regs(struct kvm_vcpu *vcpu); +static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu); static int __set_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2); @@ -1042,9 +1043,10 @@ EXPORT_SYMBOL_GPL(kvm_is_valid_cr4); void kvm_post_set_cr4(struct kvm_vcpu *vcpu, unsigned long old_cr4, unsigned long cr4) { - if (((cr4 ^ old_cr4) & KVM_MMU_CR4_ROLE_BITS) || - (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE))) + if ((cr4 ^ old_cr4) & KVM_MMU_CR4_ROLE_BITS) kvm_mmu_reset_context(vcpu); + else if (!(cr4 & X86_CR4_PCIDE) && (old_cr4 & X86_CR4_PCIDE)) + kvm_vcpu_flush_tlb_guest(vcpu); } EXPORT_SYMBOL_GPL(kvm_post_set_cr4);