Re: [Xen-devel] [PATCH 8/8] x86/AMD: Clean up context_update() in AMD VPMU code

[Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>]

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


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