From 17eed27b02da88560b4592390952b9a71042ab8b Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Tue, 31 Oct 2017 15:51:16 +0000 Subject: arm64/sve: KVM: Prevent guests from using SVE MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Until KVM has full SVE support, guests must not be allowed to execute SVE instructions. This patch enables the necessary traps, and also ensures that the traps are disabled again on exit from the guest so that the host can still use SVE if it wants to. On guest exit, high bits of the SVE Zn registers may have been clobbered as a side-effect the execution of FPSIMD instructions in the guest. The existing KVM host FPSIMD restore code is not sufficient to restore these bits, so this patch explicitly marks the CPU as not containing cached vector state for any task, thus forcing a reload on the next return to userspace. This is an interim measure, in advance of adding full SVE awareness to KVM. This marking of cached vector state in the CPU as invalid is done using __this_cpu_write(fpsimd_last_state, NULL) in fpsimd.c. Due to the repeated use of this rather obscure operation, it makes sense to factor it out as a separate helper with a clearer name. This patch factors it out as fpsimd_flush_cpu_state(), and ports all callers to use it. As a side effect of this refactoring, a this_cpu_write() in fpsimd_cpu_pm_notifier() is changed to __this_cpu_write(). This should be fine, since cpu_pm_enter() is supposed to be called only with interrupts disabled. Signed-off-by: Dave Martin Reviewed-by: Alex Bennée Reviewed-by: Christoffer Dall Acked-by: Catalin Marinas Acked-by: Marc Zyngier Cc: Ard Biesheuvel Signed-off-by: Will Deacon --- virt/kvm/arm/arm.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'virt') diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index b9f68e4add71..4d3cf9c82f5b 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -652,6 +652,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) */ preempt_disable(); + /* Flush FP/SIMD state that can't survive guest entry/exit */ + kvm_fpsimd_flush_cpu_state(); + kvm_pmu_flush_hwstate(vcpu); kvm_timer_flush_hwstate(vcpu); -- cgit