| Message ID | 20230329151747.2938509-1-tudor.ambarus@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [for,stable/linux-5.15.y] KVM: VMX: Move preemption timer <=> hrtimer dance to common x86 | expand |
On 3/29/23 17:17, Tudor Ambarus wrote: > From: Sean Christopherson<seanjc@google.com> > > commit 98c25ead5eda5e9d41abe57839ad3e8caf19500c upstream. > > Handle the switch to/from the hypervisor/software timer when a vCPU is > blocking in common x86 instead of in VMX. Even though VMX is the only > user of a hypervisor timer, the logic and all functions involved are > generic x86 (unless future CPUs do something completely different and > implement a hypervisor timer that runs regardless of mode). > > Handling the switch in common x86 will allow for the elimination of the > pre/post_blocks hooks, and also lets KVM switch back to the hypervisor > timer if and only if it was in use (without additional params). Add a > comment explaining why the switch cannot be deferred to kvm_sched_out() > or kvm_vcpu_block(). > > Signed-off-by: Sean Christopherson<seanjc@google.com> > Reviewed-by: Maxim Levitsky<mlevitsk@redhat.com> > Message-Id:<20211208015236.1616697-8-seanjc@google.com> > Signed-off-by: Paolo Bonzini<pbonzini@redhat.com> > [ta: Fix conflicts in vmx_pre_block and vmx_post_block as per Paolo's > suggestion. Add Reported-by and Link tags.] > Reported-by:syzbot+b6a74be92b5063a0f1ff@syzkaller.appspotmail.com > Link:https://syzkaller.appspot.com/bug?id=489beb3d76ef14cc6cd18125782dc6f86051a605 > Tested-by: Tudor Ambarus<tudor.ambarus@linaro.org> > Signed-off-by: Tudor Ambarus<tudor.ambarus@linaro.org> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
On Wed, Mar 29, 2023 at 03:17:47PM +0000, Tudor Ambarus wrote: > From: Sean Christopherson <seanjc@google.com> > > commit 98c25ead5eda5e9d41abe57839ad3e8caf19500c upstream. > > Handle the switch to/from the hypervisor/software timer when a vCPU is > blocking in common x86 instead of in VMX. Even though VMX is the only > user of a hypervisor timer, the logic and all functions involved are > generic x86 (unless future CPUs do something completely different and > implement a hypervisor timer that runs regardless of mode). > > Handling the switch in common x86 will allow for the elimination of the > pre/post_blocks hooks, and also lets KVM switch back to the hypervisor > timer if and only if it was in use (without additional params). Add a > comment explaining why the switch cannot be deferred to kvm_sched_out() > or kvm_vcpu_block(). > > Signed-off-by: Sean Christopherson <seanjc@google.com> > Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> > Message-Id: <20211208015236.1616697-8-seanjc@google.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > [ta: Fix conflicts in vmx_pre_block and vmx_post_block as per Paolo's > suggestion. Add Reported-by and Link tags.] > Reported-by: syzbot+b6a74be92b5063a0f1ff@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?id=489beb3d76ef14cc6cd18125782dc6f86051a605 > Tested-by: Tudor Ambarus <tudor.ambarus@linaro.org> > Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org> > --- > arch/x86/kvm/vmx/vmx.c | 6 ------ > arch/x86/kvm/x86.c | 21 +++++++++++++++++++++ > 2 files changed, 21 insertions(+), 6 deletions(-) Now queued up, thanks. greg k-h
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 9ce45554d637..c95c3675e8d5 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7597,17 +7597,11 @@ static int vmx_pre_block(struct kvm_vcpu *vcpu) if (pi_pre_block(vcpu)) return 1; - if (kvm_lapic_hv_timer_in_use(vcpu)) - kvm_lapic_switch_to_sw_timer(vcpu); - return 0; } static void vmx_post_block(struct kvm_vcpu *vcpu) { - if (kvm_x86_ops.set_hv_timer) - kvm_lapic_switch_to_hv_timer(vcpu); - pi_post_block(vcpu); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0622256cd768..5cb4af42ba64 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10043,12 +10043,28 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu) { + bool hv_timer; + if (!kvm_arch_vcpu_runnable(vcpu) && (!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) { + /* + * Switch to the software timer before halt-polling/blocking as + * the guest's timer may be a break event for the vCPU, and the + * hypervisor timer runs only when the CPU is in guest mode. + * Switch before halt-polling so that KVM recognizes an expired + * timer before blocking. + */ + hv_timer = kvm_lapic_hv_timer_in_use(vcpu); + if (hv_timer) + kvm_lapic_switch_to_sw_timer(vcpu); + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx); kvm_vcpu_block(vcpu); vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); + if (hv_timer) + kvm_lapic_switch_to_hv_timer(vcpu); + if (kvm_x86_ops.post_block) static_call(kvm_x86_post_block)(vcpu); @@ -10287,6 +10303,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) r = -EINTR; goto out; } + /* + * It should be impossible for the hypervisor timer to be in + * use before KVM has ever run the vCPU. + */ + WARN_ON_ONCE(kvm_lapic_hv_timer_in_use(vcpu)); kvm_vcpu_block(vcpu); if (kvm_apic_accept_events(vcpu) < 0) { r = 0;