Re: [PATCH] VT-x: extend LBR Broadwell errata coverage

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 20/05/2020 13:52, Jan Beulich wrote:
> For lbr_tsx_fixup_check() simply name a few more specific errata numbers.
>
> For bdf93_fixup_check(), however, more models are affected. Oddly enough
> despite being the same model and stepping, the erratum is listed for Xeon
> E3 but not its Core counterpart. With this it's of course also uncertain
> whether the absence of the erratum for Xeon D is actually meaningful.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2870,8 +2870,10 @@ static void __init lbr_tsx_fixup_check(v
>      case 0x45: /* HSM182 - 4th gen Core */
>      case 0x46: /* HSM182, HSD172 - 4th gen Core (GT3) */
>      case 0x3d: /* BDM127 - 5th gen Core */
> -    case 0x47: /* BDD117 - 5th gen Core (GT3) */
> -    case 0x4f: /* BDF85  - Xeon E5-2600 v4 */
> +    case 0x47: /* BDD117 - 5th gen Core (GT3)
> +                  BDW117 - Xeon E3-1200 v4 */
> +    case 0x4f: /* BDF85  - Xeon E5-2600 v4
> +                  BDX88  - Xeon E7-x800 v4 */

After cross referencing with Roger's errata patch, BDH75, and ...

>      case 0x56: /* BDE105 - Xeon D-1500 */
>          break;
>      default:
> @@ -2895,15 +2897,26 @@ static void __init lbr_tsx_fixup_check(v
>  static void __init bdf93_fixup_check(void)
>  {
>      /*
> -     * Broadwell erratum BDF93:
> +     * Broadwell erratum BDF93 et al:
>       *
>       * Reads from MSR_LER_TO_LIP (MSR 1DEH) may return values for bits[63:61]
>       * that are not equal to bit[47].  Attempting to context switch this 
> value
>       * may cause a #GP.  Software should sign extend the MSR.
>       */
> -    if ( boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
> -         boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model == 0x4f )
> +    if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
> +         boot_cpu_data.x86 != 6 )
> +        return;
> +
> +    switch ( boot_cpu_data.x86_model )
> +    {
> +    case 0x3d: /* BDM131 - 5th gen Core */
> +    case 0x47: /* BDD??? - 5th gen Core (H-Processor line)
> +                  BDW120 - Xeon E3-1200 v4 */
> +    case 0x4f: /* BDF93  - Xeon E5-2600 v4
> +                  BDX93  - Xeon E7-x800 v4 */

BDH80, which is "Intel® Core™ i7 Processor Family for LGA2011-v3
Socket", so high end desktop, despite being electrically compatible with
the E5 servers.

~Andrew

>          bdf93_fixup_needed = true;
> +        break;
> +    }
>  }
>  
>  static int is_last_branch_msr(u32 ecx)