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| author | Dave Martin <Dave.Martin@arm.com> | 2018-06-15 18:47:26 +0300 |
|---|---|---|
| committer | Marc Zyngier <marc.zyngier@arm.com> | 2018-06-21 11:14:44 +0300 |
| commit | 2955bcc8c309bb8f2c773db4798649aa802a491f (patch) | |
| tree | af509ec9869a2ab5c5453369728a8559b752aa99 | |
| parent | b3eb56b629d1095dde56fa37f4d7bcd5f783c8b2 (diff) | |
| download | linux-2955bcc8c309bb8f2c773db4798649aa802a491f.tar.xz | |
KVM: arm64: Avoid mistaken attempts to save SVE state for vcpus
Commit e6b673b ("KVM: arm64: Optimise FPSIMD handling to reduce
guest/host thrashing") uses fpsimd_save() to save the FPSIMD state
for a vcpu when scheduling the vcpu out. However, currently
current's value of TIF_SVE is restored before calling fpsimd_save()
which means that fpsimd_save() may erroneously attempt to save SVE
state from the vcpu. This enables current's vector state to be
polluted with guest data. current->thread.sve_state may be
unallocated or not large enough, so this can also trigger a NULL
dereference or buffer overrun.
Instead of this, TIF_SVE should be configured properly for the
guest when calling fpsimd_save() with the vcpu context loaded.
This patch ensures this by delaying restoration of current's
TIF_SVE until after the call to fpsimd_save().
Fixes: e6b673b741ea ("KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
| -rw-r--r-- | arch/arm64/kvm/fpsimd.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 98d19d1afa50..aac7808ce216 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -103,9 +103,6 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) local_irq_save(flags); - update_thread_flag(TIF_SVE, - vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE); - if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { /* Clean guest FP state to memory and invalidate cpu view */ fpsimd_save(); @@ -124,5 +121,8 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0); } + update_thread_flag(TIF_SVE, + vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE); + local_irq_restore(flags); } |