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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: 8383741ab2e7 ("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 d52d165d67c5aa26c8c89909003c94a66492d23d)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I32c7098260a44f1453bbb7f5678c6a8a5d366ee7
This commit is contained in:
Marc Zyngier
2022-05-28 12:38:11 +01:00
committed by Lee Jones
parent a11aae86d8
commit 61f4b98fe0
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;
}