Re: [win-pv-devel] [PATCH] Replace uses of MmAllocatePagesForMdlEx in __AllocatePage

[Ben Chalmers <ben.ch@xxxxxxxxxxx>]

On Mon, 2 Jul 2018 at 11:06, Paul Durrant <Paul.Durrant@xxxxxxxxxx> wrote:

> -    ASSERT(Controller->Mdl->MdlFlags & MDL_MAPPED_TO_SYSTEM_VA);
> +    ASSERT(Controller->Mdl->MdlFlags
> +            & (MDL_MAPPED_TO_SYSTEM_VA
> +                | MDL_SOURCE_IS_NONPAGED_POOL));

Do we need to change these assertions? The intent is only to assert that the MappedSystemVa field is valid, as we're about to use it.

I think we do.

MDL_MAPPED_TO_SYSTEM_VA is not set by the calls in the patch.

However, as memory gets allocated from the nonpaged pool we know it is in the kernel address space

And the macro MMGetSystemAddressForMdlSafe implies that this is the correct choice of flags for reading a valid address from MappedSystemVa

http://www.osronline.com/article.cfm?id=423 provides some supporting information

 

This appears to be a whitespace-only hunk so should be dropped or called out in the commit comment (so folks in future don't go looking for subtleties in it).

Mmm, I think I accidentally transformed some tabs into spaces somewhere along the line.  I'll try again (also removing the blank lines)

Ben 

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