[PATCH hci-8.0/hci-8.1] i386: hide la57 at fresh start for named CPU models too #VSTOR-153243

["Denis V. Lunev" <den@openvz.org>]

From: Denis V. Lunev <den@openvz.org>

x-no-la57-on-start acted only on "-cpu host", so nova host-model VMs
still triple-faulted on AMD Turin and Genoa hosts after the update.
libvirt turns host-model into a named model before building the command
line, and with no EPYC-Turin in its cpu_map that is EPYC-Genoa. la57 is
part of that definition and is not passed explicitly, so the guest keeps
it and OVMF boots Windows into its LA57 kernel.

Hide la57 for any CPU model on the same machine types unless la57=on is
given explicitly. libvirt records the filtered la57 as disabled in the
live definition for check='partial', which nova uses for host-model, so
migration, save and snapshots carry it as before.

Intel named models with la57 (Icelake-Server, SapphireRapids,
GraniteRapids) lose it on fresh start too, as "-cpu host" already does.

Fixes: 1c84596876f ("i386: hide la57 at fresh start on vz machine types that show ARCH_CAPABILITIES #VSTOR-152405")
Signed-off-by: Denis V. Lunev <den@openvz.org>
---
Applies unchanged to hci-8.0 and hci-8.1. Build-checked on both, not
yet run on an LA57 host.

 target/i386/cpu.c | 3 +--
 target/i386/cpu.h | 4 ++--
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 8d2ce279a72..e22fafeaef0 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -9116,8 +9116,7 @@ static bool x86_cpu_hide_la57(X86CPU *cpu)
 {
     CPUX86State *env = &cpu->env;
 
-    if (!cpu->no_la57_on_start || !X86_CPU_GET_CLASS(cpu)->max_features ||
-        !kvm_enabled() ||
+    if (!cpu->no_la57_on_start || !kvm_enabled() ||
         !(env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_LA57) ||
         (env->user_features[FEAT_7_0_ECX] & CPUID_7_0_ECX_LA57)) {
         return false;
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 5c1a692aca3..cbea9cf63d9 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2343,8 +2343,8 @@ struct ArchCPU {
     bool svm_features_compat;
 
     /*
-     * Virtuozzo machine types up to vz10.0.0: hide la57 from "-cpu host"
-     * when the VM starts fresh, keep it on incoming migration.
+     * Virtuozzo machine types up to vz10.0.0: hide la57 unless requested
+     * explicitly when the VM starts fresh, keep it on incoming migration.
      */
     bool no_la57_on_start;
 

base-commit: 1c84596876fb77b3e25d56cd4a4fa0c32f1faa32
-- 
2.53.0