Re: [Xen-devel] [PATCH v2 for-4.11] x86/pv: Hide more EFER bits from PV guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.05.18 at 12:00, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/pv/emul-priv-op.c
> +++ b/xen/arch/x86/pv/emul-priv-op.c
> @@ -867,9 +867,16 @@ static int read_msr(unsigned int reg, uint64_t *val,
>          return X86EMUL_OKAY;
>  
>      case MSR_EFER:
> -        *val = read_efer();
> +        /* Hide unknown bits, and unconditionally hide SVME from guests. */
> +        *val = read_efer() & EFER_KNOWN_MASK & ~EFER_SVME;
> +        /*
> +         * Hide the 64-bit features from 32-bit guests.  SCE has
> +         * vendor-dependent behaviour.
> +         */
>          if ( is_pv_32bit_domain(currd) )
> -            *val &= ~(EFER_LME | EFER_LMA | EFER_LMSLE);
> +            *val &= ~(EFER_LME | EFER_LMA | EFER_LMSLE |
> +                      (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
> +                       ? EFER_SCE : 0));
>          return X86EMUL_OKAY;

Ideally this would check the domain's x86_vendor, but that would require
wiring up emulation afaict, so fwiw
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



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