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Dave Martin 2955bcc8c3 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: e6b673b741 ("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>

2018-06-21 09:14:44 +01:00

hyp

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2018-06-12 11:34:04 -07:00

debug.c

KVM: arm64: Repurpose vcpu_arch.debug_flags for general-purpose flags

2018-05-25 12:28:13 +01:00

fpsimd.c

KVM: arm64: Avoid mistaken attempts to save SVE state for vcpus

2018-06-21 09:14:44 +01:00

guest.c

arm/arm64: KVM: Add PSCI version selection API