[PATCH v1 25/28] x86/hvm: avic: account for AMD erratum 1235

[dmukhin@xxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx>

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' bit.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/arch/x86/hvm/svm/svm.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 77f8278c598b..fd06ccfaab3f 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2536,6 +2536,21 @@ static void __init svm_avic_start(void)
      * x2APIC to guests when SVM AVIC is enabled.
      */
     svm_function_table.caps.x2apic = false;
+
+    /*
+     * 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' bit.
+     */
+    if ( boot_cpu_data.x86 == 0x17 || boot_cpu_data.x86 == 0x18 )
+    {
+        svm_avic_features &= ~AVIC_HW_ISRUNNING;
+
+        printk(XENLOG_WARNING
+               "SVM: AVIC IPI acceleration disabled (erratum 1235)\n");
+    }
 }
 
 const struct hvm_function_table * __init start_svm(void)
-- 
2.55.0