Re: [edk2-devel] [PATCH 1/1] ArmVirt: don't use unaligned CopyMem () on NOR flash

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

On Mon, 16 Jan 2023 at 12:10, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Mon, 16 Jan 2023 at 10:46, Gerd Hoffmann <kraxel@redhat.com> wrote:
> >
> > Fixes: e5ec3ba409b5 ("OvmfPkg/VirtNorFlashDxe: map flash memory as uncacheable")
> > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
>
> Thanks Gerd.
>
> I'll tweak the fixes line and the commit log a bit:
>
> Commit 789a72328553 reclassified the NOR flash region as EFI_MEMORY_WC
> in the OS visible EFI memory map, and dropped the explicit aligned
> CopyMem() implementation, in the assumption that EFI_MEMORY_WC will be
> honored by the OS, and that the region will be mapped in a way that
> tolerates misaligned accesses. However, Linux today uses device
> attributes for all EFI MMIO regions, in spite of the memory type
> attributes, and so using misaligned accesses is never safe.
>
> So instead, switch to the generic CopyMem() implementation entirely,
> just like we already did for VariableRuntimeDxe.
>
> Fixes: 789a72328553 ("OvmfPkg/VirtNorFlashDxe: use EFI_MEMORY_WC and
> drop AlignedCopyMem()")
>

Merged as #3903.

> > ---
> >  ArmVirtPkg/ArmVirtKvmTool.dsc    | 6 +++++-
> >  ArmVirtPkg/ArmVirtQemu.dsc       | 6 +++++-
> >  ArmVirtPkg/ArmVirtQemuKernel.dsc | 6 +++++-
> >  3 files changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/ArmVirtPkg/ArmVirtKvmTool.dsc b/ArmVirtPkg/ArmVirtKvmTool.dsc
> > index 2ba00bd08ff1..d0afe1b49e25 100644
> > --- a/ArmVirtPkg/ArmVirtKvmTool.dsc
> > +++ b/ArmVirtPkg/ArmVirtKvmTool.dsc
> > @@ -296,7 +296,11 @@ [Components.common]
> >        NULL|ArmVirtPkg/Library/ArmVirtTimerFdtClientLib/ArmVirtTimerFdtClientLib.inf
> >    }
> >
> > -  OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf
> > +  OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf {
> > +    <LibraryClasses>
> > +      # don't use unaligned CopyMem () on the UEFI varstore NOR flash region
> > +      BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf
> > +  }
> >
> >    MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
> >
> > diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
> > index 5dd8b6104cca..0f1c6395488a 100644
> > --- a/ArmVirtPkg/ArmVirtQemu.dsc
> > +++ b/ArmVirtPkg/ArmVirtQemu.dsc
> > @@ -428,7 +428,11 @@ [Components.common]
> >      <LibraryClasses>
> >        NULL|ArmVirtPkg/Library/ArmVirtTimerFdtClientLib/ArmVirtTimerFdtClientLib.inf
> >    }
> > -  OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf
> > +  OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf {
> > +    <LibraryClasses>
> > +      # don't use unaligned CopyMem () on the UEFI varstore NOR flash region
> > +      BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf
> > +  }
> >    MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
> >
> >    #
> > diff --git a/ArmVirtPkg/ArmVirtQemuKernel.dsc b/ArmVirtPkg/ArmVirtQemuKernel.dsc
> > index f5db3ac432f3..807c85d48285 100644
> > --- a/ArmVirtPkg/ArmVirtQemuKernel.dsc
> > +++ b/ArmVirtPkg/ArmVirtQemuKernel.dsc
> > @@ -331,7 +331,11 @@ [Components.common]
> >      <LibraryClasses>
> >        NULL|ArmVirtPkg/Library/ArmVirtTimerFdtClientLib/ArmVirtTimerFdtClientLib.inf
> >    }
> > -  OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf
> > +  OvmfPkg/VirtNorFlashDxe/VirtNorFlashDxe.inf {
> > +    <LibraryClasses>
> > +      # don't use unaligned CopyMem () on the UEFI varstore NOR flash region
> > +      BaseMemoryLib|MdePkg/Library/BaseMemoryLib/BaseMemoryLib.inf
> > +  }
> >    MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
> >
> >    #
> > --
> > 2.39.0
> >
> >
> >
> > 
> >
> >