On Wed, Sep 29 2021 at 11:31, Tony Luck wrote:
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index a58800973aed..5a3c87fd65de 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -528,6 +528,32 @@ static enum kernel_gp_hint get_kernel_gp_address(struct
> pt_regs *regs,
>
> #define GPFSTR "general protection fault"
>
> +/*
> + * When a user executes the ENQCMD instruction it will #GP
> + * fault if the IA32_PASID MSR has not been set up with a
> + * valid PASID.
> + * So if the process has been allocated a PASID (mm->pasid)
> + * AND the IA32_PASID MSR has not been initialized, try to
> + * fix this #GP by initializing the IA32_PASID MSR.
> + * If the #GP was for some other reason, it will trigger
> + * again, but this routine will return false and the #GP
> + * will be processed.
> + */
> +static void try_fixup_pasid(void)
> +{
> + if (!cpu_feature_enabled(X86_FEATURE_ENQCMD))
> + return false;
> +
> +#ifdef CONFIG_IOMMU_SUPPORT
> + if (current->mm->pasid && !current->pasid_activated) {
> + current->pasid_activated = 1;
> + wrmsrl(MSR_IA32_PASID, current->mm->pasid);
> + return true;
> + }
> +#endif
> + return false;
> +}
> +
> DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
> {
> char desc[sizeof(GPFSTR) + 50 + 2*sizeof(unsigned long) + 1] = GPFSTR;
> @@ -536,6 +562,9 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
> unsigned long gp_addr;
> int ret;
>
> + if (user_mode(regs) && try_fixup_pasid())
> + return;
> +
> cond_local_irq_enable(regs);
>
> if (static_cpu_has(X86_FEATURE_UMIP)) {
Amen.
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