Re: [PATCH] powerpc: Allow flush_(inval_)dcache_range to work across ranges >4GB

Greg Kroah-Hartman [off-list ref] writes:

On Thu, Aug 15, 2019 at 02:55:42PM +1000, Alastair D'Silva wrote:

quoted

From: Alastair D'Silva <redacted>

Heads Up: This patch cannot be submitted to Linus's tree, as the affected
assembler functions have already been converted to C.

That was done in upstream commit:

22e9c88d486a ("powerpc/64: reuse PPC32 static inline flush_dcache_range()")

Which is a larger change that we don't want to backport. This patch is a
minimal fix for stable trees.

quoted

When calling flush_(inval_)dcache_range with a size >4GB, we were masking
off the upper 32 bits, so we would incorrectly flush a range smaller
than intended.

This patch replaces the 32 bit shifts with 64 bit ones, so that
the full size is accounted for.

Signed-off-by: Alastair D'Silva <redacted>
---
 arch/powerpc/kernel/misc_64.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Acked-by: Michael Ellerman <mpe@ellerman.id.au>

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

Hi Greg,

This is "option 3", submit the patch directly, and the patch "deviates
from the original upstream patch" because the upstream patch was a
wholesale conversion from asm to C.

This patch applies cleanly to v4.14 and v4.19.

The change log should have mentioned which upstream patch it is not a
backport of, is there anything else we should have done differently to
avoid the formletter bot :)

cheers