[PATCH 3/5] dma-direct: refine dma_direct_alloc zone selection

From: Christoph Hellwig
Date: Thu Sep 27 2018 - 18:37:27 EST


We need to take the DMA offset and encryption bit into account when
selecting a zone. User the opportunity to factor out the zone
selection into a helper for reuse.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
---
kernel/dma/direct.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index f32b33cfa331..e78548397a92 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -69,6 +69,22 @@ u64 dma_direct_get_required_mask(struct device *dev)
return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
}

+static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
+ u64 *phys_mask)
+{
+ if (force_dma_unencrypted())
+ *phys_mask = __dma_to_phys(dev, dma_mask);
+ else
+ *phys_mask = dma_to_phys(dev, dma_mask);
+
+ /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
+ if (*phys_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
+ return GFP_DMA;
+ if (*phys_mask <= DMA_BIT_MASK(32))
+ return GFP_DMA32;
+ return 0;
+}
+
static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
{
return phys_to_dma_direct(dev, phys) + size - 1 <=
@@ -81,17 +97,13 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
int page_order = get_order(size);
struct page *page = NULL;
+ u64 phys_mask;
void *ret;

/* we always manually zero the memory once we are done: */
gfp &= ~__GFP_ZERO;
-
- /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
- if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
- gfp |= GFP_DMA;
- if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
- gfp |= GFP_DMA32;
-
+ gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
+ &phys_mask);
again:
/* CMA can be used only in the context which permits sleeping */
if (gfpflags_allow_blocking(gfp)) {
@@ -110,15 +122,14 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
page = NULL;

if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
- dev->coherent_dma_mask < DMA_BIT_MASK(64) &&
+ phys_mask < DMA_BIT_MASK(64) &&
!(gfp & (GFP_DMA32 | GFP_DMA))) {
gfp |= GFP_DMA32;
goto again;
}

if (IS_ENABLED(CONFIG_ZONE_DMA) &&
- dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
- !(gfp & GFP_DMA)) {
+ phys_mask < DMA_BIT_MASK(32) && !(gfp & GFP_DMA)) {
gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
goto again;
}
--
2.19.0