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Subject[PATCH v6 09/24] arm64: kvm: Unmask PMR before entering guest
Date
Interrupts masked by ICC_PMR_EL1 will not be signaled to the CPU. This
means that hypervisor will not receive masked interrupts while running a
guest.

Avoid this by making sure ICC_PMR_EL1 is unmasked when we enter a guest.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
---
arch/arm64/include/asm/kvm_host.h | 12 ++++++++++++
arch/arm64/kvm/hyp/switch.c | 16 ++++++++++++++++
2 files changed, 28 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 52fbc82..31c7e9a 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -24,6 +24,7 @@

#include <linux/types.h>
#include <linux/kvm_types.h>
+#include <asm/arch_gicv3.h>
#include <asm/cpufeature.h>
#include <asm/daifflags.h>
#include <asm/fpsimd.h>
@@ -471,6 +472,17 @@ static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
static inline void kvm_arm_vhe_guest_enter(void)
{
local_daif_mask();
+
+ /*
+ * Having IRQs masked via PMR when entering the guest means the GIC
+ * will not signal the CPU of interrupts of lower priority, and the
+ * only way to get out will be via guest exceptions.
+ * Naturally, we want to avoid this.
+ */
+ if (system_supports_irq_prio_masking()) {
+ gic_write_pmr(GIC_PRIO_IRQON);
+ dsb(sy);
+ }
}

static inline void kvm_arm_vhe_guest_exit(void)
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 7cc175c..e5ea193 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -22,6 +22,7 @@

#include <kvm/arm_psci.h>

+#include <asm/arch_gicv3.h>
#include <asm/cpufeature.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
@@ -537,6 +538,17 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
struct kvm_cpu_context *guest_ctxt;
u64 exit_code;

+ /*
+ * Having IRQs masked via PMR when entering the guest means the GIC
+ * will not signal the CPU of interrupts of lower priority, and the
+ * only way to get out will be via guest exceptions.
+ * Naturally, we want to avoid this.
+ */
+ if (system_supports_irq_prio_masking()) {
+ gic_write_pmr(GIC_PRIO_IRQON);
+ dsb(sy);
+ }
+
vcpu = kern_hyp_va(vcpu);

host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
@@ -589,6 +601,10 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
*/
__debug_switch_to_host(vcpu);

+ /* Returning to host will clear PSR.I, remask PMR if needed */
+ if (system_supports_irq_prio_masking())
+ gic_write_pmr(GIC_PRIO_IRQOFF);
+
return exit_code;
}

--
1.9.1
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