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SubjectRe: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP
On Mon, Sep 20, 2021 at 07:23:45PM +0000, Fenghua Yu wrote:
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index a58800973aed..a25d738ae839 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -61,6 +61,7 @@
> #include <asm/insn.h>
> #include <asm/insn-eval.h>
> #include <asm/vdso.h>
> +#include <asm/iommu.h>
>
> #ifdef CONFIG_X86_64
> #include <asm/x86_init.h>
> @@ -526,6 +527,14 @@ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs,
> return GP_CANONICAL;
> }
>
> +static bool fixup_pasid_exception(void)
> +{
> + if (!cpu_feature_enabled(X86_FEATURE_ENQCMD))
> + return false;
> +
> + return __fixup_pasid_exception();
> +}
> +
> #define GPFSTR "general protection fault"
>
> DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
> @@ -538,6 +547,9 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
>
> cond_local_irq_enable(regs);
>
> + if (user_mode(regs) && fixup_pasid_exception())
> + goto exit;
> +
> if (static_cpu_has(X86_FEATURE_UMIP)) {
> if (user_mode(regs) && fixup_umip_exception(regs))
> goto exit;

So you're eating any random #GP that might or might not be PASID
related. And all that witout a comment... Enlighten?

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