From: Sean Christopherson <[email protected]>
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 <[email protected]>
Reviewed-by: Maxim Levitsky <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
[ta: Fix conflicts in vmx_pre_block and vmx_post_block as per Paolo's
suggestion. Add Reported-by and Link tags.]
Reported-by: [email protected]
Link: https://syzkaller.appspot.com/bug?id=489beb3d76ef14cc6cd18125782dc6f86051a605
Tested-by: Tudor Ambarus <[email protected]>
Signed-off-by: Tudor Ambarus <[email protected]>
---
arch/x86/kvm/vmx/vmx.c | 6 ------
arch/x86/kvm/x86.c | 21 +++++++++++++++++++++
2 files changed, 21 insertions(+), 6 deletions(-)
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;
--
2.40.0.348.gf938b09366-goog
On 3/29/23 17:17, Tudor Ambarus wrote:
> From: Sean Christopherson<[email protected]>
>
> 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<[email protected]>
> Reviewed-by: Maxim Levitsky<[email protected]>
> Message-Id:<[email protected]>
> Signed-off-by: Paolo Bonzini<[email protected]>
> [ta: Fix conflicts in vmx_pre_block and vmx_post_block as per Paolo's
> suggestion. Add Reported-by and Link tags.]
> Reported-by:[email protected]
> Link:https://syzkaller.appspot.com/bug?id=489beb3d76ef14cc6cd18125782dc6f86051a605
> Tested-by: Tudor Ambarus<[email protected]>
> Signed-off-by: Tudor Ambarus<[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
On Wed, Mar 29, 2023 at 03:17:47PM +0000, Tudor Ambarus wrote:
> From: Sean Christopherson <[email protected]>
>
> 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 <[email protected]>
> Reviewed-by: Maxim Levitsky <[email protected]>
> Message-Id: <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
> [ta: Fix conflicts in vmx_pre_block and vmx_post_block as per Paolo's
> suggestion. Add Reported-by and Link tags.]
> Reported-by: [email protected]
> Link: https://syzkaller.appspot.com/bug?id=489beb3d76ef14cc6cd18125782dc6f86051a605
> Tested-by: Tudor Ambarus <[email protected]>
> Signed-off-by: Tudor Ambarus <[email protected]>
> ---
> 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