[Xen-devel] [PATCH v3 2/2] xen/arm: introduce GNTTABOP_cache_flush

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Introduce support for new hypercall GNTTABOP_cache_flush.
Use it to perform cache flashing on pages used for dma when necessary.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

---
Changes in v3:
- fix the cache maintenance op call to match what Linux does natively;
- update the hypercall interface to match Xen.

Changes in v2:
- update the hypercall interface to match Xen;
- call the interface on a single page at a time.
---
 arch/arm/xen/mm32.c                 |   27 +++++++++++++++++++++++----
 include/xen/interface/grant_table.h |   19 +++++++++++++++++++
 2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/arch/arm/xen/mm32.c b/arch/arm/xen/mm32.c
index a5a93fc..ec2eb02 100644
--- a/arch/arm/xen/mm32.c
+++ b/arch/arm/xen/mm32.c
@@ -4,6 +4,9 @@
 #include <linux/highmem.h>
 
 #include <xen/features.h>
+#include <xen/interface/grant_table.h>
+
+#include <asm/xen/hypercall.h>
 
 
 /* functions called by SWIOTLB */
@@ -22,16 +25,32 @@ static void dma_cache_maint(dma_addr_t handle, unsigned 
long offset,
                size_t len = left;
                void *vaddr;
        
+               if (len + offset > PAGE_SIZE)
+                       len = PAGE_SIZE - offset;
+
                if (!pfn_valid(pfn))
                {
-                       /* TODO: cache flush */
+                       struct gnttab_cache_flush cflush;
+
+                       cflush.op = 0;
+                       cflush.a.dev_bus_addr = pfn << PAGE_SHIFT;
+                       cflush.offset = offset;
+                       cflush.length = len;
+
+                       if (op == dmac_unmap_area && dir != DMA_TO_DEVICE)
+                               cflush.op = GNTTAB_CACHE_INVAL;
+                       if (op == dmac_map_area) {
+                               if (dir == DMA_FROM_DEVICE)
+                                       cflush.op = GNTTAB_CACHE_INVAL;
+                               else
+                                       cflush.op = GNTTAB_CACHE_CLEAN;
+                       }
+                       if (cflush.op)
+                               HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, 
&cflush, 1);
                } else {
                        struct page *page = pfn_to_page(pfn);
 
                        if (PageHighMem(page)) {
-                               if (len + offset > PAGE_SIZE)
-                                       len = PAGE_SIZE - offset;
-
                                if (cache_is_vipt_nonaliasing()) {
                                        vaddr = kmap_atomic(page);
                                        op(vaddr + offset, len, dir);
diff --git a/include/xen/interface/grant_table.h 
b/include/xen/interface/grant_table.h
index e40fae9..bcce564 100644
--- a/include/xen/interface/grant_table.h
+++ b/include/xen/interface/grant_table.h
@@ -479,6 +479,25 @@ struct gnttab_get_version {
 DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version);
 
 /*
+ * Issue one or more cache maintenance operations on a portion of a
+ * page granted to the calling domain by a foreign domain.
+ */
+#define GNTTABOP_cache_flush          12
+struct gnttab_cache_flush {
+    union {
+        uint64_t dev_bus_addr;
+        grant_ref_t ref;
+    } a;
+    uint16_t offset;   /* offset from start of grant */
+    uint16_t length;   /* size within the grant */
+#define GNTTAB_CACHE_CLEAN          (1<<0)
+#define GNTTAB_CACHE_INVAL          (1<<1)
+#define GNTTAB_CACHE_SOURCE_GREF    (1<<31)
+    uint32_t op;
+};
+DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush);
+
+/*
  * Bitfield values for update_pin_status.flags.
  */
  /* Map the grant entry for access by I/O devices. */
-- 
1.7.10.4


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