linux-kernel - [PATCH 3/6] arm64: Provide dcache_inval_poc

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Message-Id: <20251221075925.65445-1-21cnbao@gmail.com>
Date: Sun, 21 Dec 2025 15:59:25 +0800
From: Barry Song <21cnbao@...il.com>
To: robin.murphy@....com
Cc: 21cnbao@...il.com,
	ada.coupriediaz@....com,
	anshuman.khandual@....com,
	ardb@...nel.org,
	catalin.marinas@....com,
	iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	m.szyprowski@...sung.com,
	maz@...nel.org,
	ryan.roberts@....com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	will@...nel.org,
	zhengtangquan@...o.com
Subject: [PATCH 3/6] arm64: Provide dcache_inval_poc_nosync helper

On Fri, Dec 19, 2025 at 8:50 PM Robin Murphy <robin.murphy@....com> wrote:
[...]
> > diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
> > index 4a7c7e03785d..8c1043c9b9e5 100644
> > --- a/arch/arm64/mm/cache.S
> > +++ b/arch/arm64/mm/cache.S
> > @@ -132,17 +132,7 @@ alternative_else_nop_endif
> >       ret
> >   SYM_FUNC_END(dcache_clean_pou)
> >  
> > -/*
> > - *   dcache_inval_poc(start, end)
> > - *
> > - *   Ensure that any D-cache lines for the interval [start, end)
> > - *   are invalidated. Any partial lines at the ends of the interval are
> > - *   also cleaned to PoC to prevent data loss.
> > - *
> > - *   - start   - kernel start address of region
> > - *   - end     - kernel end address of region
> > - */
> > -SYM_FUNC_START(__pi_dcache_inval_poc)
> > +.macro _dcache_inval_poc_impl, do_sync
> >       dcache_line_size x2, x3
> >       sub     x3, x2, #1
> >       tst     x1, x3                          // end cache line aligned?
> > @@ -158,11 +148,42 @@ SYM_FUNC_START(__pi_dcache_inval_poc)
> >   3:  add     x0, x0, x2
> >       cmp     x0, x1
> >       b.lo    2b
> > +.if \do_sync
> >       dsb     sy
> > +.endif
>
> Similarly, don't bother with complication like this, just put the DSB in
> the one place it needs to be.
>

Thanks, Robin — great suggestion. I assume it can be:

diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
index 4a7c7e03785d..99a093d3aecb 100644
--- a/arch/arm64/mm/cache.S
+++ b/arch/arm64/mm/cache.S
@@ -132,17 +132,7 @@ alternative_else_nop_endif
 	ret
 SYM_FUNC_END(dcache_clean_pou)
 
-/*
- *	dcache_inval_poc(start, end)
- *
- * 	Ensure that any D-cache lines for the interval [start, end)
- * 	are invalidated. Any partial lines at the ends of the interval are
- *	also cleaned to PoC to prevent data loss.
- *
- *	- start   - kernel start address of region
- *	- end     - kernel end address of region
- */
-SYM_FUNC_START(__pi_dcache_inval_poc)
+.macro raw_dcache_inval_poc_macro
 	dcache_line_size x2, x3
 	sub	x3, x2, #1
 	tst	x1, x3				// end cache line aligned?
@@ -158,11 +148,41 @@ SYM_FUNC_START(__pi_dcache_inval_poc)
 3:	add	x0, x0, x2
 	cmp	x0, x1
 	b.lo	2b
+.endm
+
+/*
+ *	dcache_inval_poc(start, end)
+ *
+ * 	Ensure that any D-cache lines for the interval [start, end)
+ * 	are invalidated. Any partial lines at the ends of the interval are
+ *	also cleaned to PoC to prevent data loss.
+ *
+ *	- start   - kernel start address of region
+ *	- end     - kernel end address of region
+ */
+SYM_FUNC_START(__pi_dcache_inval_poc)
+	raw_dcache_inval_poc_macro
 	dsb	sy
 	ret
 SYM_FUNC_END(__pi_dcache_inval_poc)
 SYM_FUNC_ALIAS(dcache_inval_poc, __pi_dcache_inval_poc)
 
+/*
+ *	dcache_inval_poc_nosync(start, end)
+ *
+ * 	Issue the instructions of D-cache lines for the interval [start, end)
+ * 	for invalidation. Not necessarily cleaned to PoC till an explicit dsb
+ *	sy is issued later
+ *
+ *	- start   - kernel start address of region
+ *	- end     - kernel end address of region
+ */
+SYM_FUNC_START(__pi_dcache_inval_poc_nosync)
+	raw_dcache_inval_poc_macro
+	ret
+SYM_FUNC_END(__pi_dcache_inval_poc_nosync)
+SYM_FUNC_ALIAS(dcache_inval_poc_nosync, __pi_dcache_inval_poc_nosync)
+
 /*
  *	dcache_clean_poc(start, end)
  *
-- 

Does it look good to you?

Thanks
Barry