KVM: x86 emulator: drop unneeded call to get_segment() (99245b50) · Commits · 戴 / test

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>

arch/x86/kvm/emulate.c

+3 −6

Original line number	Diff line number	Diff line
		@@ -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)

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