From fd4021529faa931818186b6e83bd46f5de7517eb Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 10 Aug 2026 12:21:50 +0800 Subject: [PATCH] LoongArch: KVM: Fix PC double advance in kernel MMIO read fast path 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: 80edf90831a2 ("LoongArch: KVM: Add sign extension with kernel MMIO read emulation") Reviewed-by: Bibo Mao Reviewed-by: Tao Cui Signed-off-by: Zeng Chi Signed-off-by: Huacai Chen --- 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; }