Re: [PATCH v2] MdeModulePkg/NonDiscoverablePciDeviceDxe: Allow partial FreeBuffer

["Ard Biesheuvel" <ardb@kernel.org>]

On Tue, 2 Aug 2022 at 17:32, Jeff Brasen <jbrasen@nvidia.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Ard Biesheuvel <ardb@kernel.org>
> > Sent: Friday, July 29, 2022 9:48 AM
> > To: Jeff Brasen <jbrasen@nvidia.com>
> > Cc: devel@edk2.groups.io; hao.a.wu@intel.com; ray.ni@intel.com;
> > quic_llindhol@quicinc.com; ardb+tianocore@kernel.org
> > Subject: Re: [PATCH v2] MdeModulePkg/NonDiscoverablePciDeviceDxe:
> > Allow partial FreeBuffer
> >
> > External email: Use caution opening links or attachments
> >
> >
> > On Thu, 28 Jul 2022 at 13:25, Jeff Brasen <jbrasen@nvidia.com> wrote:
> > >
> > >
> > > Adding Leif/Ard to CC incase they have any comments on this patch.
> > >
> >
> > This generally looks ok to me. I just wonder if it wouldn't be simpler to reuse
> > the existing allocation descriptor if it is not being freed entirely. Given the
> > [presumably] the most common case is to allocate and then free some pages
> > at the end, lowering the page count on the existing descriptor would cover
> > most cases, and we'd only need to allocate new ones if pages are being freed
> > at the start or in the middle.
>
> There is often freeing at the beginning as well as this is being used to create a 64K aligned section of memory in the case. So it over allocates and the free's some at the beginning and the end. I could probably make it detect and use that but figured this code would support all cases and required less case specific detection.
>

Ah interesting. Would it help if the allocate routine aligned
allocations to their size?