Re: [Xen-devel] [PATCH v4 11/39] altp2m: Move (MAX|INVALID)_ALTP2M to xen/p2m-common.h

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.08.17 at 11:49, <proskurin@xxxxxxxxxxxxx> wrote:
> On 08/31/2017 10:04 AM, Jan Beulich wrote:
>>>>> On 30.08.17 at 20:32, <proskurin@xxxxxxxxxxxxx> wrote:
>>> We move the macros (MAX|INVALID)_ALTP2M out of x86-related code to
>>> common code, as the following patches will make use of them on ARM.
>> But both seem not impossible to be require arch-specific values.
> 
> Right. The general idea at this point is to move as much of altp2m
> functionality/configuration as possible into a common place. Yet, if you
> believe that, e.g., the number of altp2m views could/should diverge
> between both architectures, I will gladly move the defines back into
> arch-related parts. However, we need to consider that while x86/Intel
> supports up to 512 entries for EPT pointers as part of the VMCS, we are
> quite flexible on ARM: we manage the views entirely in software and
> hence on ARM we can easily keep up with Intel's specification. This
> allows us to hold parts of the altp2m configuration in a unified place.
> Or do you believe this is not the right way to go?

Well, you've basically answered this yourself: Why would you
want to constrain ARM just because of VMX restrictions? Requiring
all architectures to surface the same constants (regardless of
actual values) is all you need to be able to commonize code.

Jan


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