| Message ID | 20220217101242.3013716-1-oupton@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Don't miss pending interrupts for suspended vCPU | expand |
On 2022-02-17 10:12, Oliver Upton wrote: > In order to properly emulate the WFI instruction, KVM reads back > ICH_VMCR_EL2 and enables doorbells for GICv4. These preparations are > necessary in order to recognize pending interrupts in > kvm_arch_vcpu_runnable() and return to the guest. Until recently, this > work was done by kvm_arch_vcpu_{blocking,unblocking}(). Since commit > 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch > callback hook"), these callbacks were gutted and superseded by > kvm_vcpu_wfi(). > > It is important to note that KVM implements PSCI CPU_SUSPEND calls as > a WFI within the guest. However, the implementation calls directly into > kvm_vcpu_halt(), which skips the needed work done in kvm_vcpu_wfi() > to detect pending interrupts. Fix the issue by calling the WFI helper. > > Fixes: 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out > arch callback hook") > Signed-off-by: Oliver Upton <oupton@google.com> > --- > arch/arm64/kvm/psci.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c > index 3eae32876897..2ce60fecd861 100644 > --- a/arch/arm64/kvm/psci.c > +++ b/arch/arm64/kvm/psci.c > @@ -46,8 +46,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct > kvm_vcpu *vcpu) > * specification (ARM DEN 0022A). This means all suspend states > * for KVM will preserve the register state. > */ > - kvm_vcpu_halt(vcpu); > - kvm_clear_request(KVM_REQ_UNHALT, vcpu); > + kvm_vcpu_wfi(vcpu); > > return PSCI_RET_SUCCESS; > } Thanks for picking this up, I kept forgetting about fixing it. I'll merge it once I'm back home. M.
On Thu, 17 Feb 2022 10:12:42 +0000, Oliver Upton wrote: > In order to properly emulate the WFI instruction, KVM reads back > ICH_VMCR_EL2 and enables doorbells for GICv4. These preparations are > necessary in order to recognize pending interrupts in > kvm_arch_vcpu_runnable() and return to the guest. Until recently, this > work was done by kvm_arch_vcpu_{blocking,unblocking}(). Since commit > 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch > callback hook"), these callbacks were gutted and superseded by > kvm_vcpu_wfi(). > > [...] Applied to fixes, thanks! [1/1] KVM: arm64: Don't miss pending interrupts for suspended vCPU commit: a867e9d0cc15039a6ef72e17e2603303dcd1783f
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c index 3eae32876897..2ce60fecd861 100644 --- a/arch/arm64/kvm/psci.c +++ b/arch/arm64/kvm/psci.c @@ -46,8 +46,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu) * specification (ARM DEN 0022A). This means all suspend states * for KVM will preserve the register state. */ - kvm_vcpu_halt(vcpu); - kvm_clear_request(KVM_REQ_UNHALT, vcpu); + kvm_vcpu_wfi(vcpu); return PSCI_RET_SUCCESS; }
In order to properly emulate the WFI instruction, KVM reads back ICH_VMCR_EL2 and enables doorbells for GICv4. These preparations are necessary in order to recognize pending interrupts in kvm_arch_vcpu_runnable() and return to the guest. Until recently, this work was done by kvm_arch_vcpu_{blocking,unblocking}(). Since commit 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch callback hook"), these callbacks were gutted and superseded by kvm_vcpu_wfi(). It is important to note that KVM implements PSCI CPU_SUSPEND calls as a WFI within the guest. However, the implementation calls directly into kvm_vcpu_halt(), which skips the needed work done in kvm_vcpu_wfi() to detect pending interrupts. Fix the issue by calling the WFI helper. Fixes: 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch callback hook") Signed-off-by: Oliver Upton <oupton@google.com> --- arch/arm64/kvm/psci.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)