x86/pv: Rework arch_local_irq_restore() to not use popf

POPF is a rather expensive operation, so don't use it for restoring
irq flags. Instead, test whether interrupts are enabled in the flags
parameter and enable interrupts via STI in that case.

This results in the restore_fl paravirt op to be no longer needed.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210120135555.32594-7-jgross@suse.com

1 files changed, 2 insertions, 5 deletions

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 0169365f1403..de87087d3bde 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -168,16 +168,13 @@ struct pv_cpu_ops {
 struct pv_irq_ops {
 #ifdef CONFIG_PARAVIRT_XXL
 	/*
-	 * Get/set interrupt state.  save_fl and restore_fl are only
-	 * expected to use X86_EFLAGS_IF; all other bits
-	 * returned from save_fl are undefined, and may be ignored by
-	 * restore_fl.
+	 * Get/set interrupt state.  save_fl is expected to use X86_EFLAGS_IF;
+	 * all other bits returned from save_fl are undefined.
 	 *
 	 * NOTE: These functions callers expect the callee to preserve
 	 * more registers than the standard C calling convention.
 	 */
 	struct paravirt_callee_save save_fl;
-	struct paravirt_callee_save restore_fl;
 	struct paravirt_callee_save irq_disable;
 	struct paravirt_callee_save irq_enable;