x86/context-tracking: Remove exception_enter/exit() from KVM_PV_REASON_PAGE_NOT_PRESENT async page fault

This is a leftover. Page faults, just like most other exceptions,
are protected inside user_exit() / user_enter() calls in x86 entry code
when we fault from userspace. So this pair of calls is now superfluous.

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Frederic Weisbecker

arch/x86/kernel/kvm.c

@@ -245,17 +245,13 @@ NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
 dotraplinkage void
 do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 {
-	enum ctx_state prev_state;
-
 	switch (kvm_read_and_reset_pf_reason()) {
 	default:
 		do_page_fault(regs, error_code, address);
 		break;
 	case KVM_PV_REASON_PAGE_NOT_PRESENT:
 		/* page is swapped out by the host. */
-		prev_state = exception_enter();
 		kvm_async_pf_task_wait((u32)address, !user_mode(regs));
-		exception_exit(prev_state);
 		break;
 	case KVM_PV_REASON_PAGE_READY:
 		rcu_irq_enter();