From mboxrd@z Thu Jan  1 00:00:00 1970
From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Subject: Re: [PATCH 8/8] x86/AMD: Clean up context_update() in
	AMD VPMU code
Date: Thu, 11 Apr 2013 14:48:13 -0500
Message-ID: <5167137D.6000300@amd.com>
References: <1365528379-2516-1-git-send-email-boris.ostrovsky@oracle.com>
	<1365528379-2516-9-git-send-email-boris.ostrovsky@oracle.com>
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To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: jacob.shin@amd.com, haitao.shan@intel.com, jun.nakajima@intel.com, dietmar.hahn@ts.fujitsu.com, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

Boris,

I have a couple questions.  After patched, here is the final code:

static int amd_vpmu_do_rdmsr(unsigned int msr, uint64_t *msr_content)
{
     struct vcpu *v = current;
     struct vpmu_struct *vpmu = vcpu_vpmu(v);

     if ( vpmu_is_set(vpmu, VPMU_STOPPED) )
     {
         context_load(v);
         vpmu_reset(vpmu, VPMU_STOPPED);
     }

     if ( !vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
         context_read(msr, msr_content);
     else
         rdmsrl(msr, *msr_content);

     return 1;
}

1. Why do you need to call context_load() here since you checking if the 
we are in VPMU_CONTEXT_LOADED and get the appropriate copy before 
returning the msr_content?
2. If you have already called context_load() above, shouldn't you have 
to call "vpmu_set(vpmu, VPMU_CONTEXT_LOADED)" as well?  But then, you 
wouldn't be needing the latter logic, isn't it?

Suravee