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UPSTREAM: KVM: arm64: Always start with clearing SVE flag on load

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On each vcpu load, we set the KVM_ARM64_HOST_SVE_ENABLED
flag if SVE is enabled for EL0 on the host. This is used to restore
the correct state on vpcu put.

However, it appears that nothing ever clears this flag. Once
set, it will stick until the vcpu is destroyed, which has the
potential to spuriously enable SVE for userspace.

We probably never saw the issue because no VMM uses SVE, but
that's still pretty bad. Unconditionally clearing the flag
on vcpu load addresses the issue.

Bug: 254441685
Fixes: 8383741ab2 ("KVM: arm64: Get rid of host SVE tracking/saving")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220528113829.1043361-2-maz@kernel.org
(cherry picked from commit d52d165d67)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ib7f7b912890f91b6b24dc835d170a7ff3f4d827a
This commit is contained in:
Marc Zyngier
2022-05-28 12:38:11 +01:00
committed by Treehugger Robot
parent 7a0652b4ed
commit 5a5d2a512b
1 changed files with 1 additions and 0 deletions
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arch/arm64/kvm/fpsimd.c
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@@ -80,6 +80,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED;
vcpu->arch.flags |= KVM_ARM64_FP_HOST;
vcpu->arch.flags &= ~KVM_ARM64_HOST_SVE_ENABLED;
if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
}