| Message ID | 20200915170442.131635-1-alexandru.elisei@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Do not flush memslot if FWB is supported | expand |
On Tue, 15 Sep 2020 18:04:42 +0100, Alexandru Elisei wrote: > As a result of a KVM_SET_USER_MEMORY_REGION ioctl, KVM flushes the > dcache for the memslot being changed to ensure a consistent view of memory > between the host and the guest: the host runs with caches enabled, and > it is possible for the data written by the hypervisor to still be in the > caches, but the guest is running with stage 1 disabled, meaning data > accesses are to Device-nGnRnE memory, bypassing the caches entirely. > > [...] Applied to next, thanks! [1/1] KVM: arm64: Do not flush memslot if FWB is supported commit: ada329e6b5b406f33fae665e62caff7814409906 Cheers, M.
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 9a636b8064f1..c29105c6e975 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -2537,7 +2537,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, spin_lock(&kvm->mmu_lock); if (ret) unmap_stage2_range(&kvm->arch.mmu, mem->guest_phys_addr, mem->memory_size); - else + else if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) stage2_flush_memslot(kvm, memslot); spin_unlock(&kvm->mmu_lock); out:
As a result of a KVM_SET_USER_MEMORY_REGION ioctl, KVM flushes the dcache for the memslot being changed to ensure a consistent view of memory between the host and the guest: the host runs with caches enabled, and it is possible for the data written by the hypervisor to still be in the caches, but the guest is running with stage 1 disabled, meaning data accesses are to Device-nGnRnE memory, bypassing the caches entirely. Flushing the dcache is not necessary when KVM enables FWB, because it forces the guest to uses cacheable memory accesses. The current behaviour does not change, as the dcache flush helpers execute the cache operation only if FWB is not enabled, but walking the stage 2 table is avoided. Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> --- arch/arm64/kvm/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)