diff mbox

KVM: emulator: drop unneeded call to get_segment()

Message ID 20120725124942.GN26120@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Gleb Natapov July 25, 2012, 12:49 p.m. UTC 
setup_syscalls_segments() calls get_segment() and than overwrites all
but one of the structure fields and this one should also be overwritten
anyway, so we can drop call to get_segment() and avoid a couple of vmreads
on vmx. Also drop zeroing ss/cs structures since most of the fields are
set anyway. Just set those that were not set explicitly.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
--
			Gleb.
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Comments

Avi Kivity July 26, 2012, 9:21 a.m. UTC | #1 
On 07/25/2012 03:49 PM, Gleb Natapov wrote:
> setup_syscalls_segments() calls get_segment() and than overwrites all
> but one of the structure fields and this one should also be overwritten
> anyway, so we can drop call to get_segment() and avoid a couple of vmreads
> on vmx. Also drop zeroing ss/cs structures since most of the fields are
> set anyway. Just set those that were not set explicitly.
> 

Applied, thanks.
diff mbox

Patch

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 85b611e..a3d4546 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2038,12 +2038,6 @@  static void
 setup_syscalls_segments(struct x86_emulate_ctxt *ctxt,
 			struct desc_struct *cs, struct desc_struct *ss)
 {
-	u16 selector;
-
-	memset(cs, 0, sizeof(struct desc_struct));
-	ctxt->ops->get_segment(ctxt, &selector, cs, NULL, VCPU_SREG_CS);
-	memset(ss, 0, sizeof(struct desc_struct));
-
 	cs->l = 0;		/* will be adjusted later */
 	set_desc_base(cs, 0);	/* flat segment */
 	cs->g = 1;		/* 4kb granularity */
@@ -2053,6 +2047,7 @@  setup_syscalls_segments(struct x86_emulate_ctxt *ctxt,
 	cs->dpl = 0;		/* will be adjusted later */
 	cs->p = 1;
 	cs->d = 1;
+	cs->avl = 0;
 
 	set_desc_base(ss, 0);	/* flat segment */
 	set_desc_limit(ss, 0xfffff);	/* 4GB limit */
@@ -2062,6 +2057,8 @@  setup_syscalls_segments(struct x86_emulate_ctxt *ctxt,
 	ss->d = 1;		/* 32bit stack segment */
 	ss->dpl = 0;
 	ss->p = 1;
+	ss->l = 0;
+	ss->avl = 0;
 }
 
 static bool vendor_intel(struct x86_emulate_ctxt *ctxt)