On Wed, Sep 29, 2021 at 06:07:22PM +0000, Fenghua Yu wrote:
> Add
> +#ifdef CONFIG_IOMMU_SUPPORT
> because mm->pasid and current-pasid_activated are defined only if
> CONFIG_IOMMU_SUPPORT is defined.
>
> > + if (user_mode(regs) && current->mm->pasid && !current->pasid_activated)
> > {
>
> Maybe need to add "&& cpu_feature_enabled(X86_FEATURE_ENQCMD)" because
> the IA32_PASID MSR is only used when ENQCMD is enabled?
>
> > + current->pasid_activated = 1;
> > + wrmsrl(MSR_IA32_PASID, current->mm->pasid |
> > MSR_IA32_PASID_VALID);
> > + return;
> > + }
> > +
>
> +endif
New version that addresses those issues. Has ugly #ifdef in C
code :-( If that's unacceptable, then could create some stub
functions, or add a call to __try_fixup_pasid() that's in a
file in the iommu code that is only built when CONFIG_IOMMU_SUPPORT
is set. But either of those move the details far away from the
#GP handler so make extra work for anyone trying to follow along
with what is happening here.
-Tony
---
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)) {
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