From: myrslint <qemu.haziness...@passinbox.com>
Addresses this issue: https://gitlab.com/qemu-project/qemu/-/issues/2943
Most Intel CPUs in current use have self-snoop. The few added lines of
code also check for availability of the quirk disablement option so if
some CPU does not have this feature no change of behavior will occur.
---
accel/kvm/kvm-all.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 890d5ea9f8..c3d06ae2f8 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2682,6 +2682,32 @@ static int kvm_init(AccelState *as, MachineState *ms)
s->vmfd = ret;
+/* if target platform has no notion of this or kernel version does
+ * not have it there is no use for compiling this in */
+#ifdef KVM_X86_QUIRK_IGNORE_GUEST_PAT
+ /* first check for modifiable quirks bitmask */
+ ret = kvm_check_extension(s, KVM_CAP_DISABLE_QUIRKS2);
+ /* next make sure disabling it is allowed */
+ if (ret & KVM_X86_QUIRK_IGNORE_GUEST_PAT) {
+ struct kvm_enable_cap *cap;
+ cap = calloc(1, sizeof(struct kvm_enable_cap));
+ if (cap) {
+ cap->cap = KVM_CAP_DISABLE_QUIRKS2;
+ cap->args[0] = KVM_X86_QUIRK_IGNORE_GUEST_PAT;
+ /* if intel cpu does not support self-snoop this is a nop */
+ ret = kvm_vm_ioctl(s, KVM_ENABLE_CAP, cap);
+ if (ret < 0) {
+ error_printf("KVM_X86_QUIRK_IGNORE_GUEST_PAT available and "
+ "modifiable but we failed to disable it\n");
+ }
+ free(cap);
+ } else {
+ error_printf("KVM_X86_QUIRK_IGNORE_GUEST_PAT: could not "
+ "allocate memory\n");
+ }
+ }
+#endif
+
s->nr_as = kvm_vm_check_extension(s, KVM_CAP_MULTI_ADDRESS_SPACE);
if (s->nr_as <= 1) {
s->nr_as = 1;
--
2.49.1
