Re: [edk2-devel] [PATCH V3 0/4] Add New Memory Attributes

["Laszlo Ersek" <lersek@redhat.com>]

On 11/20/23 05:59, Dhaval Sharma wrote:
> Did you mean to add it as a memory type by itself like
> EFI_MEMORY_TYPE_INFORMATION?

Yes, a new enum constant for EFI_MEMORY_TYPE.

(It wasn't a "loaded question", just wanted to understand the reasoning.)

> My interpretation of Memory Type is that it is more of SW usability
> construct while Memory Attr is more of HW behavioural construct.
> Together they define how a memory region can be used.

I guess it's hard to tell apart. The SPM definition (visible in the
context below, from your earlier email) does seem like a software
usability construct ("avoid allocating for ...").

But, I truly don't know. I guess I was only trying to gauge if I could
be a useful reviewer for this series; probably not.

Thanks!
Laszlo

> 
> On Fri, Nov 17, 2023 at 1:55 PM Laszlo Ersek <lersek@redhat.com
> <mailto:lersek@redhat.com>> wrote:
> 
>     On 11/17/23 09:07, Dhaval Sharma wrote:
>     > Hi,
>     > I wanted to revisit this thread and I am maintaining the context as
>     > there are a lot of details already mentioned here
>     regarding EFI_MEMORY_SP.
>     > Other than what has been addressed here, we also would like to have an
>     > option in edk2 to *avoid* using this type of memory for its own
>     > purposes. This seems like one of the motivations for original request
>     > and is being honored by OS today but not edk2 as it does not have any
>     > specific implementation today which takes this attribute into
>     consideration.
>     > I would like to add PCD based implementation which informs edk2 NOT to
>     > use this memory for its own purposes and leave it alone (as still
>     > available memory to OS).
>     >
>     > Specific-purpose memory (SPM). The memory is earmarked for
>     > specific purposes such as for specific device drivers or applications.
>     > The SPM attribute serves as a hint to the OS to avoid allocating this
>     > memory for core OS data or code that can not be relocated.
>     > Prolonged use of this memory for purposes other than the intended
>     > purpose may result in suboptimal platform performance.
>     >
>     > Some more context:
>     > https://lwn.net/Articles/784971/ <https://lwn.net/Articles/784971/>
> 
>     Why was EFI_MEMORY_SP introduced as a memory attribute, rather than its
>     own memory type?
> 
>     Laszlo
> 
> 
> 
> -- 
> Thanks!
> =D



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