On Thu, Nov 20, 2025 at 08:46:12AM +0100, Ard Biesheuvel wrote:
> On Thu, 20 Nov 2025 at 08:03, Gerd Hoffmann via groups.io
> <[email protected]> wrote:
> >
> > On Wed, Nov 19, 2025 at 08:07:59PM +0100, Ard Biesheuvel wrote:
> > > On Wed, 19 Nov 2025 at 13:51, Gerd Hoffmann via groups.io
> > > <[email protected]> wrote:
> > > >
> > > > > > https://github.com/tianocore/edk2/pull/11770
> > > > >
> > > > > That patch did not apply cleanly on current edk2 master[46548b1].
> > > >
> > > > Just pull the branch 
> > > > (https://github.com/kraxel/edk2/tree/devel/vc-no-cmp).
> > > >
> > > > > +  CopyMem (&Hdr, FwVolHeader, sizeof (Hdr));
> > > >
> > > > > Invalid MMIO opcode (A5)
> > > >
> > > > String move instruction.  So we are trading one unsupported for another
> > > > unsupported.  Pushed an incremental fix to the branch, avoiding
> > > > CopyMem() too.
> > >
> > > Can we use MMIO accessors here instead? Any plain access might be
> > > reordered/combined to produce another unsupported opcode, no?
> >
> > I don't think so, the header can be in rom or ram too.
> 
> But on x86, MmioReadXX() can surely be used on ROM and RAM as well?

Yes, could work, given that only x86 does this dance (for historical
reasons) and arm/riscv just use VirtNorFlashDxe.  I'll try.

take care,
  Gerd



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