RE: Re: [????] Re: [PATCH] x86/bugs: Fix GDS mitigation check for CPUs without ARCH_CAP_GDS_CTRL

RE: Re: [????] Re: [PATCH] x86/bugs: Fix GDS mitigation check for CPUs without ARCH_CAP_GDS_CTRL

[Li,Rongqing]

> 
> How is that a problem? That is how it was originally implemented.
> 
> Infact, the following checks are required for the correct behavior:


You are right, I will resend this patch

Thanks

-Li

> 
>          if (mcu_ctrl & GDS_MITG_LOCKED) {
>                  if (gds_mitigation == GDS_MITIGATION_OFF)
>                          pr_warn("Mitigation locked. Disable failed.\n");
> 	...
>                  gds_mitigation = GDS_MITIGATION_FULL_LOCKED;
>          }
> 
> If the GDS microcode mitigation is locked before the kernel boot, MSR write for
> OFF will not take effect anyways. And you report OFF when the mitigation is
> locked to ON. While also triggering below WARN_ON_ONCE():
> 
> update_gds_msr()
> {
> ...
>          /*
>           * Check to make sure that the WRMSR value was not ignored.
> Writes to
>           * GDS_MITG_DIS will be ignored if this processor is locked but the
> boot
>           * processor was not.
>           */
>          rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl_after);
>          WARN_ON_ONCE(mcu_ctrl != mcu_ctrl_after);