linux-kernel - [rfc v2 4/6] dma-direct: atomic allocations must come from atomic coherent pools

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Message-ID: <alpine.DEB.2.21.2004081420060.19661@chino.kir.corp.google.com>
Date:   Wed, 8 Apr 2020 14:21:08 -0700 (PDT)
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>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: [rfc v2 4/6] dma-direct: atomic allocations must come from atomic
 coherent pools

When a device required unencrypted memory and the context does not allow
blocking, memory must be returned from the atomic coherent pools.

This avoids the remap when CONFIG_DMA_DIRECT_REMAP is not enabled and the
config only requires CONFIG_DMA_COHERENT_POOL.  This will be used for
CONFIG_AMD_MEM_ENCRYPT in a subsequent patch.

Keep all memory in these pools unencrypted.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 kernel/dma/direct.c | 16 ++++++++++++++++
 kernel/dma/pool.c   | 15 +++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 70800ca64f13..44165263c185 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -124,6 +124,18 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 	struct page *page;
 	void *ret;
 
+	/*
+	 * Unencrypted memory must come directly from DMA atomic pools if
+	 * blocking is not allowed.
+	 */
+	if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
+	    force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp)) {
+		ret = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &page, gfp);
+		if (!ret)
+			return NULL;
+		goto done;
+	}
+
 	if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
 	    dma_alloc_need_uncached(dev, attrs) &&
 	    !gfpflags_allow_blocking(gfp)) {
@@ -203,6 +215,10 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
 {
 	unsigned int page_order = get_order(size);
 
+	if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
+	    dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
+		return;
+
 	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
 	    !force_dma_unencrypted(dev)) {
 		/* cpu_addr is a struct page cookie, not a kernel address */
diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index e14c5a2da734..6685ab89cfa7 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -9,6 +9,7 @@
 #include <linux/dma-contiguous.h>
 #include <linux/init.h>
 #include <linux/genalloc.h>
+#include <linux/set_memory.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/workqueue.h>
@@ -55,12 +56,20 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
 
 	arch_dma_prep_coherent(page, pool_size);
 
+#ifdef CONFIG_DMA_DIRECT_REMAP
 	addr = dma_common_contiguous_remap(page, pool_size,
 					   pgprot_dmacoherent(PAGE_KERNEL),
 					   __builtin_return_address(0));
 	if (!addr)
 		goto free_page;
-
+#else
+	addr = page_to_virt(page);
+#endif
+	/*
+	 * Memory in the atomic DMA pools must be unencrypted, the pools do not
+	 * shrink so no re-encryption occurs in dma_direct_free_pages().
+	 */
+	set_memory_decrypted((unsigned long)page_to_virt(page), 1 << order);
 	ret = gen_pool_add_virt(pool, (unsigned long)addr, page_to_phys(page),
 				pool_size, NUMA_NO_NODE);
 	if (ret)
@@ -69,8 +78,10 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
 	return 0;
 
 remove_mapping:
+#ifdef CONFIG_DMA_DIRECT_REMAP
 	dma_common_free_remap(addr, pool_size);
-free_page:
+#endif
+free_page: __maybe_unused
 	if (!dma_release_from_contiguous(NULL, page, 1 << order))
 		__free_pages(page, order);
 out: