On Wed, Sep 29, 2021 at 07:15:53PM +0200, Thomas Gleixner wrote:
> On Wed, Sep 29 2021 at 09:59, Andy Lutomirski wrote:
> > On 9/29/21 05:28, Thomas Gleixner wrote:
> >> Looking at that patch again, none of this muck in fpu__pasid_write() is
> >> required at all. The whole exception fixup is:
> >>
> >> if (!user_mode(regs))
> >> return false;
> >>
> >> if (!current->mm->pasid)
> >> return false;
> >>
> >> if (current->pasid_activated)
> >> return false;
> >
> > <-- preemption or BH here: kaboom.
>
> Sigh, this had obviously to run in the early portion of #GP, i.e. before
> enabling interrupts.
Like this? Obviously with some comment about why this is being done.
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index a58800973aed..a848a59291e7 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -536,6 +536,12 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
unsigned long gp_addr;
int ret;
+ if (user_mode(regs) && current->mm->pasid && !current->pasid_activated)
{
+ current->pasid_activated = 1;
+ wrmsrl(MSR_IA32_PASID, current->mm->pasid |
MSR_IA32_PASID_VALID);
+ return;
+ }
+
cond_local_irq_enable(regs);
if (static_cpu_has(X86_FEATURE_UMIP)) {
-Tony
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