From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Cc: James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Oliver Upton <oliver.upton@linux.dev>,
Zenghui Yu <yuzenghui@huawei.com>
Subject: [PATCH] KVM: arm64: AArch32: Fix spurious trapping of conditional instructions
Date: Thu, 2 May 2024 18:59:56 +0100 [thread overview]
Message-ID: <20240502175956.3215496-1-maz@kernel.org> (raw)
We recently upgraded the view of ESR_EL2 to 64bit, in keeping with
the requirements of the architecture.
However, the AArch32 emulation code was left unaudited, and the
(already dodgy) code that triages whether a trap is spurious or not
(because the condition code failed) broke in a subtle way:
If ESR_EL2.ISS2 is ever non-zero (unlikely, but hey, this is the ARM
architecture we're talking about), the hack that tests the top bits
of ESR_EL2.EC will break in an interesting way.
Instead, use kvm_vcpu_trap_get_class() to obtain the EC, and list
all the possible ECs that can fail a condition code check.
While we're at it, add SMC32 to the list, as it is explicitly listed
as being allowed to trap despite failing a condition code check (as
described in the HCR_EL2.TSC documentation).
Fixes: 0b12620fddb8 ("KVM: arm64: Treat ESR_EL2 as a 64-bit register")
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/hyp/aarch32.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/hyp/aarch32.c b/arch/arm64/kvm/hyp/aarch32.c
index 8d9670e6615d..449fa58cf3b6 100644
--- a/arch/arm64/kvm/hyp/aarch32.c
+++ b/arch/arm64/kvm/hyp/aarch32.c
@@ -50,9 +50,23 @@ bool kvm_condition_valid32(const struct kvm_vcpu *vcpu)
u32 cpsr_cond;
int cond;
- /* Top two bits non-zero? Unconditional. */
- if (kvm_vcpu_get_esr(vcpu) >> 30)
+ /*
+ * These are the exception classes that could fire with a
+ * conditional instruction.
+ */
+ switch (kvm_vcpu_trap_get_class(vcpu)) {
+ case ESR_ELx_EC_CP15_32:
+ case ESR_ELx_EC_CP15_64:
+ case ESR_ELx_EC_CP14_MR:
+ case ESR_ELx_EC_CP14_LS:
+ case ESR_ELx_EC_FP_ASIMD:
+ case ESR_ELx_EC_CP10_ID:
+ case ESR_ELx_EC_CP14_64:
+ case ESR_ELx_EC_SVC32:
+ break;
+ default:
return true;
+ }
/* Is condition field valid? */
cond = kvm_vcpu_get_condition(vcpu);
--
2.39.2
reply other threads:[~2024-05-02 18:00 UTC|newest]
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