linux-kernel - [PATCH v5 14/27] arm64: kvm: Unmask PMR before entering guest

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Date:   Tue, 28 Aug 2018 16:51:24 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, daniel.thompson@...aro.org,
        joel@...lfernandes.org, marc.zyngier@....com, mark.rutland@....com,
        christoffer.dall@....com, james.morse@....com,
        catalin.marinas@....com, will.deacon@....com,
        Julien Thierry <julien.thierry@....com>,
        kvmarm@...ts.cs.columbia.edu
Subject: [PATCH v5 14/27] arm64: kvm: Unmask PMR before entering guest

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.

Tested-by: Daniel Thompson <daniel.thompson@...aro.org>
Signed-off-by: Julien Thierry <julien.thierry@....com>
Cc: Christoffer Dall <christoffer.dall@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: kvmarm@...ts.cs.columbia.edu
---
 arch/arm64/include/asm/kvm_host.h | 12 ++++++++++++
 arch/arm64/kvm/hyp/switch.c       | 17 +++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f26055f..9689592 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>
@@ -466,6 +467,17 @@ 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 (gic_prio_masking_enabled()) {
+		gic_write_pmr(ICC_PMR_EL1_UNMASKED);
+		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 d496ef5..074ab21 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>
@@ -533,6 +534,19 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
 	struct kvm_cpu_context *host_ctxt;
 	struct kvm_cpu_context *guest_ctxt;
 	u64 exit_code;
+	u32 host_pmr = ICC_PMR_EL1_UNMASKED;
+
+	/*
+	 * 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 (gic_prio_masking_enabled()) {
+		host_pmr = gic_read_pmr();
+		gic_write_pmr(ICC_PMR_EL1_UNMASKED);
+		dsb(sy);
+	}

 	vcpu = kern_hyp_va(vcpu);

@@ -586,6 +600,9 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
 	 */
 	__debug_switch_to_host(vcpu);

+	if (gic_prio_masking_enabled())
+		gic_write_pmr(host_pmr);
+
 	return exit_code;
 }

--
1.9.1