linux-kernel - Re: [PATCH 09/13] KVM: x86: save/load state on SMM switch

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Message-ID: <jpgiobxuz8g.fsf@redhat.com>
Date:	Tue, 12 May 2015 19:56:15 -0400
From:	Bandan Das <bsd@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	rkrcmar@...hat.com, guangrong.xiao@...ux.intel.com,
	Yang Zhang <yang.z.zhang@...el.com>, wanpeng.li@...ux.intel.com
Subject: Re: [PATCH 09/13] KVM: x86: save/load state on SMM switch

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 06/05/2015 19:55, Bandan Das wrote:
>> Valid point. But I would say cryptic names will always be better then
>> hex offsets. It's a one time pain in the neck to get the defines
>> right.
>> 
>> I found this header -
>> ftp://ftp.xskernel.org/soft/linux-src/bochs-20080511/cpu/smm.h
>> 
>> Maybe we can pick it up ? I can sanity check the list and
>> make sure the offsets are correct if you prefer.
>
> Thanks, I like that header. :)  No need to sanity check yourself.
>
> I'll have to adjust to define both 32-bit and 64-bit offsets.  Ok to use
> just SMRAM32_OFS_xyz and SMRAM64_OFS_xyz?  No need for LO32 and HI32, in
> particular.
Agreed, that sounds like the right thing to do.

> The one problem is that I am doing math on the offsets in some places.
> It would suck to save/restore 16 registers manually.  Any suggestions?
> I will probably send v1 for review without the offsets.

I think it's ok just to replace the offset number with a name.
If you are concerned about readability, we could probably wrap the
"for loops" in the math calculations with a more serious sounding macro
eg. "#define foreach_smm_offset(val, start_offset, jump, count)" :)

> Paolo
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