Re: [Xen-devel] [PATCH] Speculative mitigation facilities report wrong status

[Jin Nan Wang <jnwang@xxxxxxxx>]

Hi folks,

On 7/31/19 5:44 PM, Andrew Cooper wrote:
> The check for reporting MD_CLEAR must stay as X86_FEATURE_MD_CLEAR,
> because this is a property in microcode which no controls, and nothing
> further to virtualise at Xen's level.

There are two solution, which one would you like?

solution1: make sure set X86_FEATURE_SC_VERW_PV/HVM, under
X86_FEATURE_MD_CLEAR exist.

~ 1084     if ( opt_md_clear_pv && boot_cpu_has(X86_FEATURE_MD_CLEAR))
  1085         setup_force_cpu_cap(X86_FEATURE_SC_VERW_PV);
~ 1086     if ( opt_md_clear_pv || opt_md_clear_hvm &&
boot_cpu_has(X86_FEATURE_MD_CLEAR))
  1087         setup_force_cpu_cap(X86_FEATURE_SC_VERW_IDLE);
~ 1088     if ( opt_md_clear_hvm && !(caps & ARCH_CAPS_SKIP_L1DFL) &&
!opt_l1d_flush && boot_cpu_has(X86_FEATURE_MD_CLEAR))
  1089         setup_force_cpu_cap(X86_FEATURE_SC_VERW_HVM);


Solution2:

   365 #ifdef CONFIG_HVM
   366     printk("  Support for HVM VMs:%s%s%s%s%s\n",
   367            (boot_cpu_has(X86_FEATURE_SC_MSR_HVM) ||
   368             boot_cpu_has(X86_FEATURE_SC_RSB_HVM) ||
~  369             (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
boot_cpu_has(X86_FEATURE_SC_VERW_HVM)) ||
   370             opt_eager_fpu)                           ?
""               : " None",
   371            boot_cpu_has(X86_FEATURE_SC_MSR_HVM)      ? "
MSR_SPEC_CTRL" : "",
   372            boot_cpu_has(X86_FEATURE_SC_RSB_HVM)      ? "
RSB"           : "",
   373            opt_eager_fpu                             ? "
EAGER_FPU"     : "",
~  374            (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
boot_cpu_has(X86_FEATURE_SC_VERW_HVM))     ? " MD_CLEAR"      : "");
   375
   376 #endif
   377 #ifdef CONFIG_PV
   378     printk("  Support for PV VMs:%s%s%s%s%s\n",
   379            (boot_cpu_has(X86_FEATURE_SC_MSR_PV) ||
   380             boot_cpu_has(X86_FEATURE_SC_RSB_PV) ||
~  381             (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
boot_cpu_has(X86_FEATURE_SC_VERW_PV)) ||
   382             opt_eager_fpu)                           ?
""               : " None",
   383            boot_cpu_has(X86_FEATURE_SC_MSR_PV)       ? "
MSR_SPEC_CTRL" : "",
   384            boot_cpu_has(X86_FEATURE_SC_RSB_PV)       ? "
RSB"           : "",
   385            opt_eager_fpu                             ? "
EAGER_FPU"     : "",
~  386            (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
boot_cpu_has(X86_FEATURE_SC_VERW_PV))      ? " MD_CLEAR"      : "");

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