[PATCH 1/2] LoongArch: KVM: Fix PC double advance in kernel MMIO read fast path

From: Zeng Chi <[email protected]>

In the in-kernel MMIO read fast path of kvm_emu_mmio_read(),
kvm_complete_mmio_read() already advances the guest PC via update_pc().
The explicit update_pc() call right after it advances the PC a second
time, so PC moves forward by 8 instead of 4 and the instruction
following the MMIO read is silently skipped.

The user space MMIO read completion path in kvm_arch_vcpu_ioctl_run()
calls kvm_complete_mmio_read() only once, and the MMIO write fast path
advances the PC exactly once as well.

Remove the redundant update_pc() so the kernel MMIO read fast path
advances the PC by a single instruction.

Fixes: 80edf90831a2 ("LoongArch: KVM: Add sign extension with kernel MMIO read emulation")
Cc: [email protected]
Signed-off-by: Zeng Chi <[email protected]>
---
 arch/loongarch/kvm/exit.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index 8572b63478bb..482ba17bcd3d 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -481,7 +481,6 @@ int kvm_emu_mmio_read(struct kvm_vcpu *vcpu, larch_inst inst)
 		srcu_read_unlock(&vcpu->kvm->srcu, idx);
 		if (!ret) {
 			kvm_complete_mmio_read(vcpu, run);
-			update_pc(&vcpu->arch);
 			vcpu->mmio_needed = 0;
 			return EMULATE_DONE;
 		}
-- 
2.25.1


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