From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH v5 2/6] x86: allow reading MSR_IA32_TSC with
 XENPF_resource_op
Date: Thu, 22 Jan 2015 11:20:15 +0000
Message-ID: <54C0EAFF0200007800058100@mail.emea.novell.com>
References: <1421839164-26037-1-git-send-email-chao.p.peng@linux.intel.com>
	<1421839164-26037-3-git-send-email-chao.p.peng@linux.intel.com>
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To: Chao Peng <chao.p.peng@linux.intel.com>
Cc: wei.liu2@citrix.com, Ian.Campbell@citrix.com, stefano.stabellini@eu.citrix.com, Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org, will.auld@intel.com, keir@xen.org
List-Id: xen-devel@lists.xenproject.org

>>> On 21.01.15 at 12:19, <chao.p.peng@linux.intel.com> wrote:
> --- a/xen/arch/x86/platform_hypercall.c
> +++ b/xen/arch/x86/platform_hypercall.c
> @@ -61,7 +61,7 @@ long cpu_down_helper(void *data);
>  long core_parking_helper(void *data);
>  uint32_t get_cur_idle_nums(void);
>  
> -#define RESOURCE_ACCESS_MAX_ENTRIES 2
> +#define RESOURCE_ACCESS_MAX_ENTRIES 3

See my comment on an earlier version.

> @@ -75,6 +75,7 @@ static bool_t allow_access_msr(unsigned int msr)
>      /* MSR for CMT, refer to chapter 17.14 of Intel SDM. */
>      case MSR_IA32_CMT_EVTSEL:
>      case MSR_IA32_CMT_CTR:
> +    case MSR_IA32_TSC:
>          return 1;
>      }
>  
> @@ -143,10 +144,18 @@ static void resource_access(void *info)
>          switch ( entry->u.cmd )
>          {
>          case XEN_RESOURCE_OP_MSR_READ:
> -            ret = rdmsr_safe(entry->idx, entry->val);
> +            if ( entry->idx == MSR_IA32_TSC ) {

Coding style. unlikely()?

> +                entry->val = NOW();
> +                ret = 0;
> +            }
> +            else
> +                ret = rdmsr_safe(entry->idx, entry->val);
>              break;
>          case XEN_RESOURCE_OP_MSR_WRITE:
> -            ret = wrmsr_safe(entry->idx, entry->val);
> +            if ( entry->idx == MSR_IA32_TSC )

unlikely()?

Jan