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@xxxxxxxxxx>
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)
--
Gleb.
--
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