Re: [PATCH v2] powerpc: Allow flush_(inval_)dcache_range to work across ranges >4GB

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Le 26/08/2019 à 18:50, Greg Kroah-Hartman a écrit :
On Wed, Aug 21, 2019 at 10:19:27AM +1000, Alastair D'Silva wrote:
From: Alastair D'Silva <alastair@xxxxxxxxxxx>

The upstream commit:
22e9c88d486a ("powerpc/64: reuse PPC32 static inline flush_dcache_range()")
has a similar effect, but since it is a rewrite of the assembler to C, is
too invasive for stable. This patch is a minimal fix to address the issue in
assembler.

This patch applies cleanly to v5.2, v4.19 & v4.14.

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.

Changelog:
v2
   - Add related upstream commit

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

diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 1ad4089dd110..d4d096f80f4b 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S
@@ -130,7 +130,7 @@ _GLOBAL_TOC(flush_dcache_range)
  	subf	r8,r6,r4		/* compute length */
  	add	r8,r8,r5		/* ensure we get enough */
  	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)	/* Get log-2 of dcache block size */
-	srw.	r8,r8,r9		/* compute line count */
+	srd.	r8,r8,r9		/* compute line count */
  	beqlr				/* nothing to do? */
  	mtctr	r8
  0:	dcbst	0,r6
@@ -148,7 +148,7 @@ _GLOBAL(flush_inval_dcache_range)
  	subf	r8,r6,r4		/* compute length */
  	add	r8,r8,r5		/* ensure we get enough */
  	lwz	r9,DCACHEL1LOGBLOCKSIZE(r10)/* Get log-2 of dcache block size */
-	srw.	r8,r8,r9		/* compute line count */
+	srd.	r8,r8,r9		/* compute line count */
  	beqlr				/* nothing to do? */
  	sync
  	isync

I need an ack from the powerpc maintainer(s) before I can take this.

I think you already got an ack (on v1). See https://patchwork.ozlabs.org/patch/1147403/#2239663

Christophe



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