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From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Peter Shier <pshier@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH] KVM: arm64: Don't miss pending interrupts for suspended vCPU
Date: Thu, 17 Feb 2022 10:12:42 +0000	[thread overview]
Message-ID: <20220217101242.3013716-1-oupton@google.com> (raw)

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callback hook"), these callbacks were gutted and superseded by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;
 }
-- 
2.35.1.265.g69c8d7142f-goog

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	James Morse <james.morse@arm.com>,
	 Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	 linux-arm-kernel@lists.infradead.org,
	Peter Shier <pshier@google.com>,
	 Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	 Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	 Oliver Upton <oupton@google.com>
Subject: [PATCH] KVM: arm64: Don't miss pending interrupts for suspended vCPU
Date: Thu, 17 Feb 2022 10:12:42 +0000	[thread overview]
Message-ID: <20220217101242.3013716-1-oupton@google.com> (raw)

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;
 }
-- 
2.35.1.265.g69c8d7142f-goog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Oliver Upton <oupton@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Peter Shier <pshier@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Oliver Upton <oupton@google.com>
Subject: [PATCH] KVM: arm64: Don't miss pending interrupts for suspended vCPU
Date: Thu, 17 Feb 2022 10:12:42 +0000	[thread overview]
Message-ID: <20220217101242.3013716-1-oupton@google.com> (raw)

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;
 }
-- 
2.35.1.265.g69c8d7142f-goog


             reply	other threads:[~2022-02-17 10:12 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-17 10:12 Oliver Upton [this message]
2022-02-17 10:12 ` [PATCH] KVM: arm64: Don't miss pending interrupts for suspended vCPU Oliver Upton
2022-02-17 10:12 ` Oliver Upton
2022-02-17 13:40 ` Marc Zyngier
2022-02-17 13:40   ` Marc Zyngier
2022-02-17 13:40   ` Marc Zyngier
2022-02-17 16:30 ` Marc Zyngier
2022-02-17 16:30   ` Marc Zyngier
2022-02-17 16:30   ` Marc Zyngier

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