From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v2 07/14] svm: Remove redundant TSC scaling
 in svm_set_tsc_offset()
Date: Mon, 7 Dec 2015 13:25:23 -0500
Message-ID: <5665CF13.8060707@oracle.com>
References: <1449435529-12989-1-git-send-email-haozhong.zhang@intel.com>
	<1449435529-12989-8-git-send-email-haozhong.zhang@intel.com>
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To: Haozhong Zhang <haozhong.zhang@intel.com>, xen-devel@lists.xen.org
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>, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
List-Id: xen-devel@lists.xenproject.org

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.

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);
>           }