From mboxrd@z Thu Jan  1 00:00:00 1970
From: Haozhong Zhang <haozhong.zhang@intel.com>
Subject: Re: [PATCH v2 07/14] svm: Remove redundant TSC scaling
 in svm_set_tsc_offset()
Date: Tue, 8 Dec 2015 09:54:37 +0800
Message-ID: <20151208015437.GG3547@hz-desktop.sh.intel.com>
References: <1449435529-12989-1-git-send-email-haozhong.zhang@intel.com>
	<1449435529-12989-8-git-send-email-haozhong.zhang@intel.com>
	<5665CF13.8060707@oracle.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Content-Disposition: inline
In-Reply-To: <5665CF13.8060707@oracle.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Keir Fraser <keir@xen.org>, Jan Beulich <jbeulich@suse.com>, Jun Nakajima <jun.nakajima@intel.com>, Andrew Cooper <andrew.cooper3@citrix.com>, xen-devel@lists.xen.org, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
List-Id: xen-devel@lists.xenproject.org

On 12/07/15 13:25, Boris Ostrovsky wrote:
> On 12/06/2015 03:58 PM, Haozhong Zhang wrote:
> >Now every caller passes an already scaled offset to
> >svm_set_tsc_offset(), so it's not necessary to recalculate a scaled TSC
> >offset in svm_set_tsc_offset().
> >
> >Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> >---
> >  xen/arch/x86/hvm/svm/svm.c | 15 ++-------------
> >  1 file changed, 2 insertions(+), 13 deletions(-)
> >
> >diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> >index 9d5f2c3..3d22dfa 100644
> >--- a/xen/arch/x86/hvm/svm/svm.c
> >+++ b/xen/arch/x86/hvm/svm/svm.c
> >@@ -826,19 +826,7 @@ static void svm_set_tsc_offset(struct vcpu *v, u64 offset, u64 at_tsc)
> >      struct vmcb_struct *n1vmcb, *n2vmcb;
> >      uint64_t n2_tsc_offset = 0;
> >      struct domain *d = v->domain;
> >-    uint64_t host_tsc, guest_tsc;
> >-
> >-    guest_tsc = hvm_get_guest_tsc_fixed(v, at_tsc);
> >-
> >-    /* Re-adjust the offset value when TSC_RATIO is available */
> >-    if ( cpu_has_tsc_ratio && !d->arch.vtsc )
> >-    {
> >-        if ( at_tsc )
> >-            host_tsc = at_tsc;
> >-        else
> >-            host_tsc = rdtsc();
> >-        offset = svm_get_tsc_offset(host_tsc, guest_tsc, vcpu_tsc_ratio(v));
> >-    }
> >+    uint64_t guest_tsc;
> 
> You could declare it at the first use site below.
>

will move to the first use site.

Haozhong

> Other than that,
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> 
> >      if ( !nestedhvm_enabled(d) ) {
> >          vmcb_set_tsc_offset(vmcb, offset);
> >@@ -854,6 +842,7 @@ static void svm_set_tsc_offset(struct vcpu *v, u64 offset, u64 at_tsc)
> >          n2_tsc_offset = vmcb_get_tsc_offset(n2vmcb) -
> >              vmcb_get_tsc_offset(n1vmcb);
> >          if ( svm->ns_tscratio != DEFAULT_TSC_RATIO ) {
> >+            guest_tsc = hvm_get_guest_tsc_fixed(v, at_tsc);
> >              n2_tsc_offset = svm_get_tsc_offset(guest_tsc,
> >                  guest_tsc + n2_tsc_offset, svm->ns_tscratio);
> >          }
>