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KVM: arm64: Flush the instruction cache if not unmapping the VM on reboot

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On a system with FWB, we don't need to unmap Stage-2 on reboot,
as even if userspace takes this opportunity to repaint the whole
of memory, FWB ensures that the data side stays consistent even
if the guest uses non-cacheable mappings.

However, the I-side is not necessarily coherent with the D-side
if CTR_EL0.DIC is 0. In this case, invalidate the i-cache to
preserve coherency.

Reported-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Fixes: 892713e97c ("KVM: arm64: Sidestep stage2_unmap_vm() on vcpu reset when S2FWB is supported")
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2020-05-30 17:22:19 +01:00
parent 8f7f4fe756
commit 7ae2f3db61
1 changed files with 10 additions and 4 deletions
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14
arch/arm64/kvm/arm.c
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@ -989,11 +989,17 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
* Ensure a rebooted VM will fault in RAM pages and detect if the
* guest MMU is turned off and flush the caches as needed.
*
* S2FWB enforces all memory accesses to RAM being cacheable, we
* ensure that the cache is always coherent.
* S2FWB enforces all memory accesses to RAM being cacheable,
* ensuring that the data side is always coherent. We still
* need to invalidate the I-cache though, as FWB does *not*
* imply CTR_EL0.DIC.
*/
if (vcpu->arch.has_run_once && !cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
stage2_unmap_vm(vcpu->kvm);
if (vcpu->arch.has_run_once) {
if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
stage2_unmap_vm(vcpu->kvm);
else
__flush_icache_all();
}
vcpu_reset_hcr(vcpu);