Re: [edk2-devel] [PATCH v2] MdeModulePkg/NonDiscoverablePciDeviceDxe: Allow partial FreeBuffer

["Jeff Brasen" <jbrasen@nvidia.com>]

MdeModulePkg maintainers, Any comments on this?

> -----Original Message-----
> From: Ard Biesheuvel <ardb@kernel.org>
> Sent: Wednesday, September 21, 2022 10:32 AM
> To: devel@edk2.groups.io; Jeff Brasen <jbrasen@nvidia.com>
> Cc: hao.a.wu@intel.com; ray.ni@intel.com; quic_llindhol@quicinc.com;
> ardb+tianocore@kernel.org
> Subject: Re: [edk2-devel] [PATCH v2]
> MdeModulePkg/NonDiscoverablePciDeviceDxe: Allow partial FreeBuffer
> 
> External email: Use caution opening links or attachments
> 
> 
> On Wed, 21 Sept 2022 at 18:27, Jeff Brasen via groups.io
> <jbrasen=nvidia.com@groups.io> wrote:
> >
> > Anything else needed to get this merged?
> >
> 
> That is up to the MdeModulePkg maintainers.
> 
> > > -----Original Message-----
> > > From: Ard Biesheuvel <ardb@kernel.org>
> > > Sent: Thursday, September 8, 2022 9:55 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: [edk2-devel] [PATCH v2]
> > > MdeModulePkg/NonDiscoverablePciDeviceDxe: Allow partial FreeBuffer
> > >
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > On Thu, 8 Sept 2022 at 17:39, Jeff Brasen <jbrasen@nvidia.com> wrote:
> > > >
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Ard Biesheuvel <ardb@kernel.org>
> > > > > Sent: Monday, August 15, 2022 8:42 AM
> > > > > To: devel@edk2.groups.io; Jeff Brasen <jbrasen@nvidia.com>
> > > > > Cc: hao.a.wu@intel.com; ray.ni@intel.com;
> > > > > quic_llindhol@quicinc.com;
> > > > > ardb+tianocore@kernel.org
> > > > > Subject: Re: [edk2-devel] [PATCH v2]
> > > > > MdeModulePkg/NonDiscoverablePciDeviceDxe: Allow partial
> > > > > FreeBuffer
> > > > >
> > > > > External email: Use caution opening links or attachments
> > > > >
> > > > >
> > > > > On Fri, 5 Aug 2022 at 18:56, Jeff Brasen via groups.io
> > > > > <jbrasen=nvidia.com@groups.io> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Ard Biesheuvel <ardb@kernel.org>
> > > > > > > Sent: Tuesday, August 2, 2022 10:51 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 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?
> > > > > >
> > > > > > The PciIo->AllocateBuffer function doesn't support passing the
> > > > > > request in so
> > > > > we would need to know that info beforehand. The current calling
> > > > > in the XHCI driver does a free at the beginning and then the end
> > > > > of the buffer so we could the existing allocation tracker but
> > > > > figured it would be better to correct the function just in case
> > > > > someone called it to free
> > > in the middle.
> > > > > >
> > > > >
> > > > > What I was wondering is whether such allocations are themselves
> > > > > multiples of 64k. This is perhaps orthogonal to the issue this
> > > > > patch addresses, as we'' still need to deal with partial free
> > > > > calls regardless. But I was curious whether XHCI in particular,
> > > > > and perhaps more generally, we could streamline this by aligning
> > > > > all allocations
> > > to a log2 upper bound of their sizes.
> > > >
> > > > Xhci code
> > >
> (https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Bus/Pci/
> > > Xhci
> > > Dxe/UsbHcMem.c#L604) in allocation requested is greater the
> > > EFI_PAGE_SIZE allocates number of requested pages plus pages for the
> > > alignment and then frees pages at the beginning and end of the
> > > allocation.  I am not sure we really could change this without adding an
> alignment field to the PciIo protocol.
> > > >
> > > > Is there anything else you would like to change on this patch?
> > > >
> > >
> > > No. Thanks for the clarification.
> > >
> > > Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> >
> >
> > 
> >
> >