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authorDave Martin <Dave.Martin@arm.com>2018-06-15 16:47:26 +0100
committerMarc Zyngier <marc.zyngier@arm.com>2018-06-21 09:14:44 +0100
commit2955bcc8c309bb8f2c773db4798649aa802a491f (patch)
treeaf509ec9869a2ab5c5453369728a8559b752aa99 /arch/arm64
parentb3eb56b629d1095dde56fa37f4d7bcd5f783c8b2 (diff)
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>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kvm/fpsimd.c6
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);
}