From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: [PATCH] KVM: emulator: drop unneeded call to get_segment() Date: Wed, 25 Jul 2012 15:49:42 +0300 Message-ID: <20120725124942.GN26120@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: avi@redhat.com, mtosatti@redhat.com To: kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43120 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756172Ab2GYMtn (ORCPT ); Wed, 25 Jul 2012 08:49:43 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q6PCnh20022157 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 25 Jul 2012 08:49:43 -0400 Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: 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 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.