linux-kernel - [rfc 3/6] dma-remap: wire up the atomic pools depending on gfp mask

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Date:   Sun, 1 Mar 2020 16:05:16 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Christoph Hellwig <hch@....de>,
        Tom Lendacky <thomas.lendacky@....com>
cc:     "Singh, Brijesh" <brijesh.singh@....com>,
        "Grimm, Jon" <jon.grimm@....com>, Joerg Roedel <joro@...tes.org>,
        baekhw@...gle.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: [rfc 3/6] dma-remap: wire up the atomic pools depending on gfp
 mask


When allocating non-blockable memory, determine the optimal gfp mask of
the device and use the appropriate atomic pool.

The coherent DMA mask will remain the same between allocation and free
and, thus, memory will be freed to the same atomic pool it was allocated
from.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 include/linux/dma-direct.h |  2 ++
 kernel/dma/direct.c        |  6 +++---
 kernel/dma/remap.c         | 34 ++++++++++++++++++++++++++--------
 3 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -67,6 +67,8 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size,
 }
 
 u64 dma_direct_get_required_mask(struct device *dev);
+gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
+				  u64 *phys_mask);
 void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		gfp_t gfp, unsigned long attrs);
 void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -44,8 +44,8 @@ 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_limit)
+gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
+				  u64 *phys_limit)
 {
 	u64 dma_limit = min_not_zero(dma_mask, dev->bus_dma_limit);
 
@@ -88,7 +88,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 
 	/* we always manually zero the memory once we are done: */
 	gfp &= ~__GFP_ZERO;
-	gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
+	gfp |= dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
 			&phys_limit);
 	page = dma_alloc_contiguous(dev, alloc_size, gfp);
 	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -188,28 +188,44 @@ static int __init dma_atomic_pool_init(void)
 }
 postcore_initcall(dma_atomic_pool_init);
 
+static inline struct gen_pool *dev_to_pool(struct device *dev)
+{
+	u64 phys_mask;
+	gfp_t gfp;
+
+	gfp = dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
+					  &phys_mask);
+	if (IS_ENABLED(CONFIG_ZONE_DMA) && gfp == GFP_DMA)
+		return atomic_pool;
+	if (IS_ENABLED(CONFIG_ZONE_DMA32) && gfp == GFP_DMA32)
+		return atomic_pool_dma32;
+	return atomic_pool_normal;
+}
+
 static bool dma_in_atomic_pool(struct device *dev, void *start, size_t size)
 {
-	if (unlikely(!atomic_pool))
-		return false;
+	struct gen_pool *pool = dev_to_pool(dev);
 
-	return gen_pool_has_addr(atomic_pool, (unsigned long)start, size);
+	if (unlikely(!pool))
+		return false;
+	return gen_pool_has_addr(pool, (unsigned long)start, size);
 }
 
 void *dma_alloc_from_pool(struct device *dev, size_t size,
 			  struct page **ret_page, gfp_t flags)
 {
+	struct gen_pool *pool = dev_to_pool(dev);
 	unsigned long val;
 	void *ptr = NULL;
 
-	if (!atomic_pool) {
-		WARN(1, "coherent pool not initialised!\n");
+	if (!pool) {
+		WARN(1, "%pGg atomic pool not initialised!\n", &flags);
 		return NULL;
 	}
 
-	val = gen_pool_alloc(atomic_pool, size);
+	val = gen_pool_alloc(pool, size);
 	if (val) {
-		phys_addr_t phys = gen_pool_virt_to_phys(atomic_pool, val);
+		phys_addr_t phys = gen_pool_virt_to_phys(pool, val);
 
 		*ret_page = pfn_to_page(__phys_to_pfn(phys));
 		ptr = (void *)val;
@@ -221,9 +237,11 @@ void *dma_alloc_from_pool(struct device *dev, size_t size,
 
 bool dma_free_from_pool(struct device *dev, void *start, size_t size)
 {
+	struct gen_pool *pool = dev_to_pool(dev);
+
 	if (!dma_in_atomic_pool(dev, start, size))
 		return false;
-	gen_pool_free(atomic_pool, (unsigned long)start, size);
+	gen_pool_free(pool, (unsigned long)start, size);
 	return true;
 }
 #endif /* CONFIG_DMA_DIRECT_REMAP */