linux-kernel - [PATCH v6 03/21] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support

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Message-Id: <20210518094725.7701-4-will@kernel.org>
Date:   Tue, 18 May 2021 10:47:07 +0100
From:   Will Deacon <will@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Qais Yousef <qais.yousef@....com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Quentin Perret <qperret@...gle.com>, Tejun Heo <tj@...nel.org>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, kernel-team@...roid.com
Subject: [PATCH v6 03/21] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support

If a vCPU is caught running 32-bit code on a system with mismatched
support at EL0, then we should kill it.

Acked-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Will Deacon <will@...nel.org>
---
 arch/arm64/kvm/arm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 1cb39c0803a4..5bdba97a7654 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -692,6 +692,15 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 	}
 }
 
+static bool vcpu_mode_is_bad_32bit(struct kvm_vcpu *vcpu)
+{
+	if (likely(!vcpu_mode_is_32bit(vcpu)))
+		return false;
+
+	return !system_supports_32bit_el0() ||
+		static_branch_unlikely(&arm64_mismatched_32bit_el0);
+}
+
 /**
  * kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
  * @vcpu:	The VCPU pointer
@@ -875,7 +884,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		 * with the asymmetric AArch32 case), return to userspace with
 		 * a fatal error.
 		 */
-		if (!system_supports_32bit_el0() && vcpu_mode_is_32bit(vcpu)) {
+		if (vcpu_mode_is_bad_32bit(vcpu)) {
 			/*
 			 * As we have caught the guest red-handed, decide that
 			 * it isn't fit for purpose anymore by making the vcpu
-- 
2.31.1.751.gd2f1c929bd-goog