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SubjectRe: [PATCH RFC V3 7/9] x86/entry: Preserve PKRS MSR across exceptions
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On 10/9/20 12:42 PM, ira.weiny@intel.com wrote:
> @@ -341,6 +341,9 @@ noinstr void irqentry_enter(struct pt_regs *regs, irqentry_state_t *state)
> /* Use the combo lockdep/tracing function */
> trace_hardirqs_off();
> instrumentation_end();
> +
> +done:
> + irq_save_pkrs(state);
> }

One nit: This saves *and* sets PKRS. It's not obvious from the call
here that PKRS is altered at this site. Seems like there could be a
better name.

Even if we did:

irq_save_set_pkrs(state, INIT_VAL);

It would probably compile down to the same thing, but be *really*
obvious what's going on.

> void irqentry_exit_cond_resched(void)
> @@ -362,7 +365,12 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t *state)
> /* Check whether this returns to user mode */
> if (user_mode(regs)) {
> irqentry_exit_to_user_mode(regs);
> - } else if (!regs_irqs_disabled(regs)) {
> + return;
> + }
> +
> + irq_restore_pkrs(state);
> +
> + if (!regs_irqs_disabled(regs)) {
> /*
> * If RCU was not watching on entry this needs to be done
> * carefully and needs the same ordering of lockdep/tracing
>

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