On 02/05/20 06:32, Sean Christopherson wrote:
> Make get_dr6() and set_dr6() optional and drop the VMX implementations,
> which are for all intents and purposes nops. This avoids a retpoline on
> VMX when reading/writing DR6, at minimal cost (~1 uop) to SVM.
Can't get_dr6 be killed off completely here, since vcpu->arch.dr6 is the
only value that is ever passed to set_dr6? OTOH no complaint about
adding the if for vmx_set_dr6, since that will also be covered nicely by
DEFINE_STATIC_COND_CALL.
Paolo
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx/vmx.c | 11 -----------
> arch/x86/kvm/x86.c | 6 ++++--
> 2 files changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index de18cd386bb1..e157bdc218ea 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5008,15 +5008,6 @@ static int handle_dr(struct kvm_vcpu *vcpu)
> return kvm_skip_emulated_instruction(vcpu);
> }
>
> -static u64 vmx_get_dr6(struct kvm_vcpu *vcpu)
> -{
> - return vcpu->arch.dr6;
> -}
> -
> -static void vmx_set_dr6(struct kvm_vcpu *vcpu, unsigned long val)
> -{
> -}
> -
> static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu)
> {
> get_debugreg(vcpu->arch.db[0], 0);
> @@ -7799,8 +7790,6 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
> .set_idt = vmx_set_idt,
> .get_gdt = vmx_get_gdt,
> .set_gdt = vmx_set_gdt,
> - .get_dr6 = vmx_get_dr6,
> - .set_dr6 = vmx_set_dr6,
> .set_dr7 = vmx_set_dr7,
> .sync_dirty_debug_regs = vmx_sync_dirty_debug_regs,
> .cache_reg = vmx_cache_reg,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8ec356ac1e6e..eccbfcb6a4e5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1069,7 +1069,8 @@ static void kvm_update_dr0123(struct kvm_vcpu *vcpu)
>
> static void kvm_update_dr6(struct kvm_vcpu *vcpu)
> {
> - if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))
> + if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) &&
> + kvm_x86_ops.set_dr6)
> kvm_x86_ops.set_dr6(vcpu, vcpu->arch.dr6);
> }
>
> @@ -1148,7 +1149,8 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
> case 4:
> /* fall through */
> case 6:
> - if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
> + if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) ||
> + !kvm_x86_ops.get_dr6)
> *val = vcpu->arch.dr6;
> else
> *val = kvm_x86_ops.get_dr6(vcpu);
>
