Re: [PATCH] MdeModulePkg: Correct high-memory use in NvmExpressDxe

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

On Thu, 24 Feb 2022 at 12:58, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Thu, 24 Feb 2022 at 12:48, Tomas Pilar <quic_tpilar@quicinc.com> wrote:
> >
> > Delay and move the allocation and mapping of memory that backs the DMA
> > engine in NvmExpress devices to NvmeInit() to ensure that
> > the allocation only happens after the
> > EFI_PCI_IO_ATTRIBUTE_DUAL_ADDRESS_CYCLE attribute is set
> > on the PciIo controller.
> >
> > This ensures that the DMA-backing memory is not forcibly allocated
> > below 4G in system address map. Otherwise the allocation fails on
> > platforms that do not have any memory below the 4G mark and the drive
> > initialisation fails.
> >
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> > Cc: Leif Lindholm <leif@nuviainc.com>
> > Signed-off-by: Tomas Pilar <quic_tpilar@quicinc.com>
>
> NvmeControllerInit () can be called multiple times, no? So you should
> probably make sure that the buffer is not allocated and mapped again
> if one already exists.
>

Alternatively, you could move all PCI attribute handling into the
start() hook. Other drivers keep it there as well, and it seems like a
more natural place for it (given the fact that NvmeControllerInit() is
also called on a host controller reset)