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LoongArch: KVM: Fix PC double advance in kernel MMIO read fast path

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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 bytes 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.

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

Cc: stable@vger.kernel.org
Fixes: 80edf90831 ("LoongArch: KVM: Add sign extension with kernel MMIO read emulation")
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Zeng Chi 2026-08-10 12:21:50 +08:00 committed by Huacai Chen
parent 01c823f14e
commit fd4021529f
1 changed files with 0 additions and 1 deletions
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1
arch/loongarch/kvm/exit.c
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@ -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;
}