[Xen-devel] [PATCH v1 1/1] xen/arm: Map mmio-sram nodes as cached memory

["Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx>]

From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxxx>

Relax the mapping of mmio-sram nodes that do not set the
no-memory-wc property to cached normal memory.

Rationale:
Allthough on chip memories are relatively fast compared to
off-chip memories, large OCMs are still significantly slower
than L1 caches. Depending on the memory, either cached or
uncached may make most sense.

Also, dom0 may like to use the memory in a cache-coherent way
to avoid SW managed coherency.

By mapping it cached at S2, we let dom0 select cacheability
via S1 mappings.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxxxxx>
---
 xen/arch/arm/domain_build.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 07b868d..3a7c1ee 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -56,8 +56,20 @@ static const struct dt_device_match dev_map_attrs[] 
__initconst =
         .data = (void *) (uintptr_t) p2m_mmio_direct_dev,
     },
     {
+        /*
+         * Allthough on chip memories are relatively fast compared to
+         * off-chip memories, large OCMs are still significantly slower
+         * than L1 caches. Depending on the memory, either cached or
+         * uncached may make most sense.
+         *
+         * Also, dom0 may like to use the memory in a cache-coherent
+         * way to avoid SW managed coherency.
+         *
+         * By mapping it cached at S2, we let dom0 select cacheability
+         * via S1 mappings.
+         */
         __DT_MATCH_COMPATIBLE("mmio-sram"),
-        .data = (void *) (uintptr_t) p2m_mmio_direct_nc,
+        .data = (void *) (uintptr_t) p2m_mmio_direct_c,
     },
     { /* sentinel */ },
 };
-- 
2.7.4


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