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

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

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.


> > -----Original Message-----
> > From: Jeff Brasen
> > Sent: Friday, June 17, 2022 9:39 AM
> > To: devel@edk2.groups.io
> > Cc: hao.a.wu@intel.com; ray.ni@intel.com
> > Subject: RE: [PATCH v2] MdeModulePkg/NonDiscoverablePciDeviceDxe:
> > Allow partial FreeBuffer
> >
> > Any thoughts on this patch?
> >
> > > -----Original Message-----
> > > From: Jeff Brasen <jbrasen@nvidia.com>
> > > Sent: Monday, February 14, 2022 11:46 AM
> > > To: devel@edk2.groups.io
> > > Cc: hao.a.wu@intel.com; ray.ni@intel.com; Jeff Brasen
> > > <jbrasen@nvidia.com>
> > > Subject: [PATCH v2] MdeModulePkg/NonDiscoverablePciDeviceDxe: Allow
> > > partial FreeBuffer
> > >
> > > Add support for partial free of non cached buffers.
> > > If a request for less than the full size is requested new allocations
> > > for the remaining head and tail of the buffer are added to the list.
> > > Added verification that Buffer is EFI_PAGE_SIZE aligned.
> > > The XHCI driver does this if the page size for the controller is >4KB.
> > >
> > > Signed-off-by: Jeff Brasen <jbrasen@nvidia.com>
> > > ---
> > >  .../NonDiscoverablePciDeviceIo.c              | 53 ++++++++++++++++++-
> > >  1 file changed, 51 insertions(+), 2 deletions(-)
> > >
> > > diff --git
> > >
> > a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverable
> > > PciDeviceIo.c
> > >
> > b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverable
> > > PciDeviceIo.c
> > > index c1c5c6267c..77809cfedf 100644
> > > ---
> > >
> > a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverable
> > > PciDeviceIo.c
> > > +++
> > >
> > b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverable
> > > Pc
> > > +++ iDeviceIo.c
> > > @@ -960,12 +960,23 @@ NonCoherentPciIoFreeBuffer (
> > >    LIST_ENTRY                                   *Entry;
> > >    EFI_STATUS                                   Status;
> > >    NON_DISCOVERABLE_DEVICE_UNCACHED_ALLOCATION  *Alloc;
> > > +  NON_DISCOVERABLE_DEVICE_UNCACHED_ALLOCATION  *AllocHead;
> > > + NON_DISCOVERABLE_DEVICE_UNCACHED_ALLOCATION  *AllocTail;
> > >    BOOLEAN                                      Found;
> > > +  UINTN                                        StartPages;
> > > +  UINTN                                        EndPages;
> > > +
> > > +  if (HostAddress != ALIGN_POINTER (HostAddress, EFI_PAGE_SIZE)) {
> > > +    ASSERT_EFI_ERROR (EFI_INVALID_PARAMETER);
> > > +    return EFI_INVALID_PARAMETER;
> > > +  }
> > >
> > >    Dev = NON_DISCOVERABLE_PCI_DEVICE_FROM_PCI_IO (This);
> > >
> > >    Found = FALSE;
> > >    Alloc = NULL;
> > > +  AllocHead = NULL;
> > > +  AllocTail = NULL;
> > >
> > >    //
> > >    // Find the uncached allocation list entry associated @@ -976,9
> > > +987,13 @@ NonCoherentPciIoFreeBuffer (
> > >         Entry = Entry->ForwardLink)
> > >    {
> > >      Alloc = BASE_CR (Entry,
> > > NON_DISCOVERABLE_DEVICE_UNCACHED_ALLOCATION, List);
> > > -    if ((Alloc->HostAddress == HostAddress) && (Alloc->NumPages ==
> > Pages))
> > > {
> > > +    StartPages = 0;
> > > +    if (Alloc->HostAddress < HostAddress) {
> > > +      StartPages = (HostAddress - Alloc->HostAddress) / EFI_PAGE_SIZE;
> > > +    }
> > > +    if ((Alloc->HostAddress <= HostAddress) && (Alloc->NumPages >=
> > > + (Pages + StartPages))) {
> > >        //
> > > -      // We are freeing the exact allocation we were given
> > > +      // We are freeing at least part of what we were given
> > >        // before by AllocateBuffer()
> > >        //
> > >        Found = TRUE;
> > > @@ -991,7 +1006,41 @@ NonCoherentPciIoFreeBuffer (
> > >      return EFI_NOT_FOUND;
> > >    }
> > >
> > > +  EndPages = Alloc->NumPages - (Pages + StartPages);
> > > +
> > > +  if (StartPages != 0) {
> > > +    AllocHead = AllocatePool (sizeof *AllocHead);
> > > +    if (AllocHead == NULL) {
> > > +      return EFI_OUT_OF_RESOURCES;
> > > +    }
> > > +
> > > +    AllocHead->HostAddress = Alloc->HostAddress;
> > > +    AllocHead->NumPages = StartPages;
> > > +    AllocHead->Attributes = Alloc->Attributes;  }
> > > +
> > > +  if (EndPages != 0) {
> > > +    AllocTail = AllocatePool (sizeof *AllocTail);
> > > +    if (AllocTail == NULL) {
> > > +      return EFI_OUT_OF_RESOURCES;
> > > +    }
> > > +
> > > +    AllocTail->HostAddress = Alloc->HostAddress + ((Pages +
> > > + StartPages) *
> > > EFI_PAGE_SIZE);
> > > +    AllocTail->NumPages = EndPages;
> > > +    AllocTail->Attributes = Alloc->Attributes;  }
> > > +
> > >    RemoveEntryList (&Alloc->List);
> > > +  //
> > > +  // Record this new sub allocations in the linked list, so we  //
> > > + can restore the memory space attributes later  //  if (AllocHead !=
> > > + NULL) {
> > > +    InsertHeadList (&Dev->UncachedAllocationList, &AllocHead->List);
> > > + } if (AllocTail != NULL) {
> > > +    InsertHeadList (&Dev->UncachedAllocationList, &AllocTail->List);
> > > + }
> > >
> > >    Status = gDS->SetMemorySpaceAttributes (
> > >                    (EFI_PHYSICAL_ADDRESS)(UINTN)HostAddress,
> > > --
> > > 2.17.1
>