On 02/03/2017 23:07, Stefano Stabellini wrote:
On Thu, 2 Mar 2017, Edgar E. Iglesias wrote:
On Thu, Mar 02, 2017 at 02:39:55PM -0800, Stefano Stabellini wrote:
On Thu, 2 Mar 2017, Julien Grall wrote:
Hi Stefano,
On 02/03/17 19:12, Stefano Stabellini wrote:
On Thu, 2 Mar 2017, Julien Grall wrote:
On 02/03/17 08:53, Edgar E. Iglesias wrote:
On Thu, Mar 02, 2017 at 09:38:37AM +0100, Edgar E. Iglesias wrote:
On Wed, Mar 01, 2017 at 05:05:21PM -0800, Stefano Stabellini wrote:
Julien, from looking at the two diffs, this is simpler and nicer, but if
you look at xen/include/asm-arm/page.h, my patch made
clean_dcache_va_range consistent with invalidate_dcache_va_range. For
consistency, I would prefer to deal with the two functions the same way.
Although it is not a spec requirement, I also think that it is a good
idea to issue cache flushes from cacheline aligned addresses, like
invalidate_dcache_va_range does and Linux does, to make more obvious
what is going on.
invalid_dcache_va_range is split because the cache instruction differs for the
start and end if unaligned. For them you want to use clean & invalidate rather
than invalidate.
If you look at the implementation of other cache helpers in Linux (see
dcache_by_line_op in arch/arm64/include/asm/assembler.h), they will only align
start & end.
I don't think so, unless I am reading dcache_by_line_op wrong.
Also, the invalid_dcache_va_range is using modulo which I would rather avoid.
The modulo in this case will not be optimized by the compiler because
cacheline_bytes is not a constant.
That is a good point. What if I replace the modulo op with
p & (cacheline_bytes - 1)
in invalidate_dcache_va_range, then add the similar code to
clean_dcache_va_range and clean_and_invalidate_dcache_va_range?
Yeah, if there was some kind of generic ALIGN or ROUND_DOWN macro we could do:
--- a/xen/include/asm-arm/page.h
+++ b/xen/include/asm-arm/page.h
@@ -325,7 +325,9 @@ static inline int clean_dcache_va_range(const void *p,
unsigned long size)
{
const void *end;
dsb(sy); /* So the CPU issues all writes to the range */
- for ( end = p + size; p < end; p += cacheline_bytes )
+
+ p = (void *)ALIGN((uintptr_t)p, cacheline_bytes);
+ end = (void *)ROUNDUP((uintptr_t)p + size, cacheline_bytes);
Even simpler:
end = p + size;
p = (void *)ALIGN((uintptr_t)p, cacheline_bytes);
We don't have any ALIGN macro in Xen and the way we use the term align
in xen is very similar to ROUNDUP.
However a simple p = (void *)((uintptr_t)p & ~(cacheline_bytes - 1))
should work here.
Cheers,
--
Julien Grall
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