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From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	David Brazdil <dbrazdil@google.com>,
	Eric Auger <eric.auger@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Qian Cai <qcai@redhat.com>,
	Shannon Zhao <shannon.zhao@linux.alibaba.com>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	kernel-team@android.com, kvmarm@lists.cs.columbia.edu,
	kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: [PATCH 01/18] KVM: arm64: Don't access PMCR_EL0 when no PMU is available
Date: Thu,  7 Jan 2021 11:20:44 +0000	[thread overview]
Message-ID: <20210107112101.2297944-2-maz@kernel.org> (raw)
In-Reply-To: <20210107112101.2297944-1-maz@kernel.org>

We reset the guest's view of PMCR_EL0 unconditionally, based on
the host's view of this register. It is however legal for an
implementation not to provide any PMU, resulting in an UNDEF.

The obvious fix is to skip the reset of this shadow register
when no PMU is available, sidestepping the issue entirely.
If no PMU is available, the guest is not able to request
a virtual PMU anyway, so not doing nothing is the right thing
to do!

It is unlikely that this bug can hit any HW implementation
though, as they all provide a PMU. It has been found using nested
virt with the host KVM not implementing the PMU itself.

Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register")
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201210083059.1277162-1-maz@kernel.org
---
 arch/arm64/kvm/sys_regs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3313dedfa505..d46e7f706cb0 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -594,6 +594,10 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 {
 	u64 pmcr, val;
 
+	/* No PMU available, PMCR_EL0 may UNDEF... */
+	if (!kvm_arm_support_pmu_v3())
+		return;
+
 	pmcr = read_sysreg(pmcr_el0);
 	/*
 	 * Writable bits of PMCR_EL0 (ARMV8_PMU_PMCR_MASK) are reset to UNKNOWN
-- 
2.29.2


WARNING: multiple messages have this Message-ID
From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kernel-team@android.com, kvm@vger.kernel.org,
	Qian Cai <qcai@redhat.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Shannon Zhao <shannon.zhao@linux.alibaba.com>,
	linux-arm-kernel@lists.infradead.org,
	Nathan Chancellor <natechancellor@gmail.com>,
	kvmarm@lists.cs.columbia.edu
Subject: [PATCH 01/18] KVM: arm64: Don't access PMCR_EL0 when no PMU is available
Date: Thu,  7 Jan 2021 11:20:44 +0000	[thread overview]
Message-ID: <20210107112101.2297944-2-maz@kernel.org> (raw)
In-Reply-To: <20210107112101.2297944-1-maz@kernel.org>

We reset the guest's view of PMCR_EL0 unconditionally, based on
the host's view of this register. It is however legal for an
implementation not to provide any PMU, resulting in an UNDEF.

The obvious fix is to skip the reset of this shadow register
when no PMU is available, sidestepping the issue entirely.
If no PMU is available, the guest is not able to request
a virtual PMU anyway, so not doing nothing is the right thing
to do!

It is unlikely that this bug can hit any HW implementation
though, as they all provide a PMU. It has been found using nested
virt with the host KVM not implementing the PMU itself.

Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register")
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201210083059.1277162-1-maz@kernel.org
---
 arch/arm64/kvm/sys_regs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3313dedfa505..d46e7f706cb0 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -594,6 +594,10 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 {
 	u64 pmcr, val;
 
+	/* No PMU available, PMCR_EL0 may UNDEF... */
+	if (!kvm_arm_support_pmu_v3())
+		return;
+
 	pmcr = read_sysreg(pmcr_el0);
 	/*
 	 * Writable bits of PMCR_EL0 (ARMV8_PMU_PMCR_MASK) are reset to UNKNOWN
-- 
2.29.2

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

WARNING: multiple messages have this Message-ID
From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	kernel-team@android.com, kvm@vger.kernel.org,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Qian Cai <qcai@redhat.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Shannon Zhao <shannon.zhao@linux.alibaba.com>,
	Eric Auger <eric.auger@redhat.com>,
	James Morse <james.morse@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Nathan Chancellor <natechancellor@gmail.com>,
	David Brazdil <dbrazdil@google.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	Julien Thierry <julien.thierry.kdev@gmail.com>
Subject: [PATCH 01/18] KVM: arm64: Don't access PMCR_EL0 when no PMU is available
Date: Thu,  7 Jan 2021 11:20:44 +0000	[thread overview]
Message-ID: <20210107112101.2297944-2-maz@kernel.org> (raw)
In-Reply-To: <20210107112101.2297944-1-maz@kernel.org>

We reset the guest's view of PMCR_EL0 unconditionally, based on
the host's view of this register. It is however legal for an
implementation not to provide any PMU, resulting in an UNDEF.

The obvious fix is to skip the reset of this shadow register
when no PMU is available, sidestepping the issue entirely.
If no PMU is available, the guest is not able to request
a virtual PMU anyway, so not doing nothing is the right thing
to do!

It is unlikely that this bug can hit any HW implementation
though, as they all provide a PMU. It has been found using nested
virt with the host KVM not implementing the PMU itself.

Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register")
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201210083059.1277162-1-maz@kernel.org
---
 arch/arm64/kvm/sys_regs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3313dedfa505..d46e7f706cb0 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -594,6 +594,10 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 {
 	u64 pmcr, val;
 
+	/* No PMU available, PMCR_EL0 may UNDEF... */
+	if (!kvm_arm_support_pmu_v3())
+		return;
+
 	pmcr = read_sysreg(pmcr_el0);
 	/*
 	 * Writable bits of PMCR_EL0 (ARMV8_PMU_PMCR_MASK) are reset to UNKNOWN
-- 
2.29.2


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

  reply	other threads:[~2021-01-07 11:22 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-07 11:20 [GIT PULL] KVM/arm64 fixes for 5.11, take #1 Marc Zyngier
2021-01-07 11:20 ` Marc Zyngier
2021-01-07 11:20 ` Marc Zyngier
2021-01-07 11:20 ` Marc Zyngier [this message]
2021-01-07 11:20   ` [PATCH 01/18] KVM: arm64: Don't access PMCR_EL0 when no PMU is available Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 02/18] KVM: arm64: Prevent use of invalid PSCI v0.1 function IDs Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 03/18] KVM: arm64: Use lm_alias in nVHE-only VA conversion Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 04/18] KVM: arm64: Skip computing hyp VA layout for VHE Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 05/18] KVM: arm64: Minor cleanup of hyp variables used in host Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 06/18] KVM: arm64: Remove unused includes in psci-relay.c Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 07/18] KVM: arm64: Move skip_host_instruction to adjust_pc.h Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 08/18] KVM: arm64: Declutter host PSCI 0.1 handling Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 09/18] KVM: Documentation: Add arm64 KVM_RUN error codes Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 10/18] KVM: arm64: arch_timer: Remove VGIC initialization check Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 11/18] KVM: arm64: Move double-checked lock to kvm_vgic_map_resources() Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 12/18] KVM: arm64: Update comment in kvm_vgic_map_resources() Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 13/18] KVM: arm64: Remove redundant call to kvm_pmu_vcpu_reset() Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 14/18] KVM: arm64: Consolidate dist->ready setting into kvm_vgic_map_resources() Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 15/18] KVM: arm64: Fix hyp_cpu_pm_{init,exit} __init annotation Marc Zyngier
2021-01-07 11:20   ` [PATCH 15/18] KVM: arm64: Fix hyp_cpu_pm_{init, exit} " Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20 ` [PATCH 16/18] KVM: arm64: Remove spurious semicolon in reg_to_encoding() Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:20   ` Marc Zyngier
2021-01-07 11:21 ` [PATCH 17/18] KVM: arm64: Replace KVM_ARM_PMU with HW_PERF_EVENTS Marc Zyngier
2021-01-07 11:21   ` Marc Zyngier
2021-01-07 11:21   ` Marc Zyngier
2021-01-07 11:21 ` [PATCH 18/18] arm64: cpufeature: remove non-exist CONFIG_KVM_ARM_HOST Marc Zyngier
2021-01-07 11:21   ` Marc Zyngier
2021-01-07 11:21   ` Marc Zyngier
2021-01-07 18:19 ` [GIT PULL] KVM/arm64 fixes for 5.11, take #1 Paolo Bonzini
2021-01-07 18:19   ` Paolo Bonzini
2021-01-07 18:19   ` Paolo Bonzini
2021-01-07 23:09 ` Paolo Bonzini
2021-01-07 23:09   ` Paolo Bonzini
2021-01-07 23:09   ` Paolo Bonzini
2021-01-08  8:22   ` Marc Zyngier
2021-01-08  8:22     ` Marc Zyngier
2021-01-08  8:22     ` Marc Zyngier
2021-01-08 10:03     ` Paolo Bonzini
2021-01-08 10:03       ` Paolo Bonzini
2021-01-08 10:03       ` Paolo Bonzini

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