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Subject: Re: [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when
 SEV-SNP VM terminates
To:     Sean Christopherson <seanjc@google.com>
References: <20210707183616.5620-1-brijesh.singh@amd.com>
 <20210707183616.5620-26-brijesh.singh@amd.com> <YPHnb5pW9IoTcwWU@google.com>
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From:   Brijesh Singh <brijesh.singh@amd.com>
Message-ID: <1e9ea39d-ed68-ad91-63f8-661245b62dfe@amd.com>
Date:   Tue, 20 Jul 2021 13:23:34 -0500
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On 7/20/21 11:40 AM, Sean Christopherson wrote:
> On Mon, Jul 19, 2021, Brijesh Singh wrote:
>>
>> On 7/19/21 2:03 PM, Sean Christopherson wrote:
>>> On Mon, Jul 19, 2021, Brijesh Singh wrote:
>>> Ah, not firmwrare, gotcha.  But we can still use a helper, e.g. an inner
>>> double-underscore helper, __rmp_make_private().
>>
>> In that case we are basically passing the all the fields defined in the
>> 'struct rmpupdate' as individual arguments.
> 
> Yes, but (a) not _all_ fields, (b) it would allow hiding "struct rmpupdate", and
> (c) this is much friendlier to readers:
> 
> 	__rmp_make_private(pfn, gpa, PG_LEVEL_4K, svm->asid, true);
> 
> than:
> 
> 	rmpupdate(&rmpupdate);
> 

Ok.

> For the former, I can see in a single line of code that KVM is creating a 4k
> private, immutable guest page.  With the latter, I need to go hunt down all code
> that modifies rmpupdate to understand what the code is doing.
> 
>> How about something like this:
>>
>> * core kernel exports the rmpupdate()
>> * the include/linux/sev.h header file defines the helper functions
>>
>>    int rmp_make_private(u64 pfn, u64 gpa, int psize, int asid)
> 
> I think we'll want s/psize/level, i.e. make it more obvious clear that the input
> is PG_LEVEL_*.
> 

ok, I will stick to x86 PG_LEVEL_*

thanks