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

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

On 11/3/26 10:27 PM, Denis V. Lunev wrote:
> 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

Ack
Applied to hci-8.0 and hci-dev