linux-kernel - Re: [PATCH 2/5] KVM: SVM: Optimize nested svm msrpm merging

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Message-ID: <4B87C835.4080409@redhat.com>
Date:	Fri, 26 Feb 2010 15:10:13 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Alexander Graf <agraf@...e.de>,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] KVM: SVM: Optimize nested svm msrpm merging

On 02/26/2010 03:04 PM, Joerg Roedel wrote:
>
>> I'm still not convinced on this way of doing things. If it's static,
>> make it static. If it's dynamic, make it dynamic. Dynamically
>> generating a static list just sounds plain wrong to me.
>>      
> Stop. I had a static list in the first version of the patch. This list
> was fine except the fact that a developer needs to remember to update
> this list if the list of non-intercepted msrs is expanded. The whole
> reason for a dynamically built list is to take the task of maintaining
> the list away from the developer and remove a possible source of hard to
> find bugs. This is what the current approach does.
>    

The problem was the two lists.  If you had a

static struct svm_direct_access_msrs = {
     u32 index;
     bool longmode_only;
} direct_access_msrs = {
    ...
};

You could generate

static unsigned *msrpm_offsets_longmode, *msrpm_offsets_legacy;

as well as the original bitmaps at module init, no?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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