KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)

Hygon Family 18h CPUs are derived from AMD Family 17h (Zen1) silicon and
share the same erratum #1235: hardware may read a stale IsRunning=1 bit
during ICR write emulation and silently fail to generate an
AVIC_IPI_FAILURE_TARGET_NOT_RUNNING VM-Exit on the sending vCPU.

The absence of the VM-Exit causes KVM to miss the required wakeup of
blocking target vCPUs, leading to hung vCPUs and unbounded delays in
guest execution.

Extend the existing AMD Family 17h erratum #1235 workaround to also cover
Hygon Family 18h.  With IPI virtualization disabled, KVM never sets
IsRunning=1 in the Physical ID table, so every non-self IPI generates a
VM-Exit and is correctly emulated.

Fixes: 8de4a1c ("KVM: SVM: Disable (x2)AVIC IPI virtualization if CPU has erratum #1235")
Cc: <stable@vger.kernel.org>
Signed-off-by: Tina Zhang <zhang_wei@open-hieco.net>
Message-ID: <20260522040014.3380201-1-zhang_wei@open-hieco.net>

Author: Tina Zhang

arch/x86/kvm/svm/avic.c

@@ -1300,12 +1300,14 @@ bool __init avic_hardware_setup(void)
 	}
 
 	/*
-	 * Disable IPI virtualization for AMD Family 17h CPUs (Zen1 and Zen2)
-	 * due to erratum 1235, which results in missed VM-Exits on the sender
-	 * and thus missed wake events for blocking vCPUs due to the CPU
-	 * failing to see a software update to clear IsRunning.
+	 * Disable IPI virtualization for AMD Family 17h (Zen1 and Zen2) and
+	 * Hygon Family 18h (derived from AMD Zen1) CPUs due to erratum 1235,
+	 * which results in missed VM-Exits on the sender and thus missed wake
+	 * events for blocking vCPUs due to the CPU failing to see a software
+	 * update to clear IsRunning.
 	 */
-	enable_ipiv = enable_ipiv && boot_cpu_data.x86 != 0x17;
+	if (boot_cpu_data.x86 == 0x17 || boot_cpu_data.x86 == 0x18)
+		enable_ipiv = false;
 
 	amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);