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authorAndrew Jones <drjones@redhat.com>2019-08-22 13:03:05 +0200
committerMarc Zyngier <maz@kernel.org>2019-08-22 13:19:56 +0100
commit2113c5f62b7423e4a72b890bd479704aa85c81ba (patch)
tree348406b3194e49fb49bba929fcaae8f2ba1bca13
parent16e604a437c89751dc626c9e90cf88ba93c5be64 (diff)
KVM: arm/arm64: Only skip MMIO insn once
If after an MMIO exit to userspace a VCPU is immediately run with an immediate_exit request, such as when a signal is delivered or an MMIO emulation completion is needed, then the VCPU completes the MMIO emulation and immediately returns to userspace. As the exit_reason does not get changed from KVM_EXIT_MMIO in these cases we have to be careful not to complete the MMIO emulation again, when the VCPU is eventually run again, because the emulation does an instruction skip (and doing too many skips would be a waste of guest code :-) We need to use additional VCPU state to track if the emulation is complete. As luck would have it, we already have 'mmio_needed', which even appears to be used in this way by other architectures already. Fixes: 0d640732dbeb ("arm64: KVM: Skip MMIO insn after emulation") Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
-rw-r--r--virt/kvm/arm/mmio.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c
index a8a6a0c883f1..6af5c91337f2 100644
--- a/virt/kvm/arm/mmio.c
+++ b/virt/kvm/arm/mmio.c
@@ -86,6 +86,12 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
unsigned int len;
int mask;
+ /* Detect an already handled MMIO return */
+ if (unlikely(!vcpu->mmio_needed))
+ return 0;
+
+ vcpu->mmio_needed = 0;
+
if (!run->mmio.is_write) {
len = run->mmio.len;
if (len > sizeof(unsigned long))
@@ -188,6 +194,7 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
run->mmio.is_write = is_write;
run->mmio.phys_addr = fault_ipa;
run->mmio.len = len;
+ vcpu->mmio_needed = 1;
if (!ret) {
/* We handled the access successfully in the kernel. */