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KVM: x86 emulator: drop unneeded call to get_segment() 

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>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Gleb Natapov 2012-07-25 15:49:42 +03:00 committed by Avi Kivity
parent f23b070e66
commit 99245b507d
1 changed files with 3 additions and 6 deletions
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9
arch/x86/kvm/emulate.c
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@ -2035,12 +2035,6 @@ 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 */
@ -2050,6 +2044,7 @@ 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 */
@ -2059,6 +2054,8 @@ 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)