linux-kernel - [PATCH 2/2] x86/context-tracking: Remove exception_enter/exit() from KVM_PV_REASON_PAGE_NOT

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Date:   Fri, 27 Dec 2019 17:36:12 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Andy Lutomirski <luto@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: [PATCH 2/2] 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 useless.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: Wanpeng Li <wanpengli@...cent.com>
Cc: Jim Mattson <jmattson@...gle.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kernel/kvm.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 32ef1ee733b7..81045aabb6f4 100644
--- a/arch/x86/kernel/kvm.c
+++ b/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();
-- 
2.23.0