linux-kernel - [PATCH] x86: svm: use kvm_fast_pio

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Message-ID: <20150228000134.11870.31357.stgit@joelvmguard2.amd.com>
Date:	Fri, 27 Feb 2015 18:01:34 -0600
From:	Joel Schopp <joel.schopp@....com>
To:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, <kvm@...r.kernel.org>
CC:	David Kaplan <David.Kaplan@....com>,
	David Kaplan <david.kaplan@....com>, <rkrcmar@...hat.com>,
	Joerg Roedel <joro@...tes.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	<linux-kernel@...r.kernel.org>, <--bcc=ssg.sos.patches@....com>,
	Borislav Petkov <bp@...en8.de>
Subject: [PATCH] x86: svm: use kvm_fast_pio_in()

From: David Kaplan <David.Kaplan@....com>

We can make the in instruction go faster the same way the out instruction is
already.

Signed-off-by: David Kaplan <David.Kaplan@....com>
[extracted from larger unlrelated patch, forward ported, tested]
Signed-off-by: Joel Schopp <joel.schopp@....com>
---
 arch/x86/kvm/svm.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d319e0c..f8c906b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1899,7 +1899,7 @@ static int io_interception(struct vcpu_svm *svm)
 	++svm->vcpu.stat.io_exits;
 	string = (io_info & SVM_IOIO_STR_MASK) != 0;
 	in = (io_info & SVM_IOIO_TYPE_MASK) != 0;
-	if (string || in)
+	if (string)
 		return emulate_instruction(vcpu, 0) == EMULATE_DONE;
 
 	port = io_info >> 16;
@@ -1907,6 +1907,8 @@ static int io_interception(struct vcpu_svm *svm)
 	svm->next_rip = svm->vmcb->control.exit_info_2;
 	skip_emulated_instruction(&svm->vcpu);
 
+	if (in)
+		return kvm_fast_pio_in(vcpu, size, port);
 	return kvm_fast_pio_out(vcpu, size, port);
 }
 

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