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

4 files changed, 0 insertions, 54 deletions

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 6abf3f248197..dc0a337f985b 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1035,8 +1035,6 @@ void __init xen_setup_vcpu_info_placement(void)
 	 */
 	if (xen_have_vcpu_info_placement) {
 		pv_ops.irq.save_fl = __PV_IS_CALLEE_SAVE(xen_save_fl_direct);
-		pv_ops.irq.restore_fl =
-			__PV_IS_CALLEE_SAVE(xen_restore_fl_direct);
 		pv_ops.irq.irq_disable =
 			__PV_IS_CALLEE_SAVE(xen_irq_disable_direct);
 		pv_ops.irq.irq_enable =
diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
index 850c93f346c7..dfa091d79c2e 100644
--- a/arch/x86/xen/irq.c
+++ b/arch/x86/xen/irq.c
@@ -42,28 +42,6 @@ asmlinkage __visible unsigned long xen_save_fl(void)
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
 
-__visible void xen_restore_fl(unsigned long flags)
-{
-	struct vcpu_info *vcpu;
-
-	/* convert from IF type flag */
-	flags = !(flags & X86_EFLAGS_IF);
-
-	/* See xen_irq_enable() for why preemption must be disabled. */
-	preempt_disable();
-	vcpu = this_cpu_read(xen_vcpu);
-	vcpu->evtchn_upcall_mask = flags;
-
-	if (flags == 0) {
-		barrier(); /* unmask then check (avoid races) */
-		if (unlikely(vcpu->evtchn_upcall_pending))
-			xen_force_evtchn_callback();
-		preempt_enable();
-	} else
-		preempt_enable_no_resched();
-}
-PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
-
 asmlinkage __visible void xen_irq_disable(void)
 {
 	/* There's a one instruction preempt window here.  We need to
@@ -118,7 +96,6 @@ static void xen_halt(void)
 
 static const struct pv_irq_ops xen_irq_ops __initconst = {
 	.save_fl = PV_CALLEE_SAVE(xen_save_fl),
-	.restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 	.irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 	.irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 1d738c5957f5..02f31341e435 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -72,34 +72,6 @@ SYM_FUNC_START(xen_save_fl_direct)
 	ret
 SYM_FUNC_END(xen_save_fl_direct)
 
-
-/*
- * In principle the caller should be passing us a value return from
- * xen_save_fl_direct, but for robustness sake we test only the
- * X86_EFLAGS_IF flag rather than the whole byte. After setting the
- * interrupt mask state, it checks for unmasked pending events and
- * enters the hypervisor to get them delivered if so.
- */
-SYM_FUNC_START(xen_restore_fl_direct)
-	FRAME_BEGIN
-	testw $X86_EFLAGS_IF, %di
-	setz PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
-	/*
-	 * Preempt here doesn't matter because that will deal with any
-	 * pending interrupts.  The pending check may end up being run
-	 * on the wrong CPU, but that doesn't hurt.
-	 */
-
-	/* check for unmasked and pending */
-	cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
-	jnz 1f
-	call check_events
-1:
-	FRAME_END
-	ret
-SYM_FUNC_END(xen_restore_fl_direct)
-
-
 /*
  * Force an event check by making a hypercall, but preserve regs
  * before making the call.
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index b2fd80a01a36..8d7ec49a35fb 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -131,7 +131,6 @@ static inline void __init xen_efi_init(struct boot_params *boot_params)
 __visible void xen_irq_enable_direct(void);
 __visible void xen_irq_disable_direct(void);
 __visible unsigned long xen_save_fl_direct(void);
-__visible void xen_restore_fl_direct(unsigned long);
 
 __visible unsigned long xen_read_cr2(void);
 __visible unsigned long xen_read_cr2_direct(void);