linux-kernel - [PATCH 1/2] Revert "remoteproc: qcom_q6v5_mss: map/unmap metadata region before/after use"

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Date:   Fri, 23 Dec 2022 10:27:02 +0100
From:   Christoph Hellwig <hch@....de>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>
Cc:     linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux.dev
Subject: [PATCH 1/2] Revert "remoteproc: qcom_q6v5_mss: map/unmap metadata region before/after use"

This reverts commit fc156629b23a21181e473e60341e3a78af25a1d4.

This commit manages to do three API violations at once:

 - dereference the return value of dma_alloc_attrs with the
   DMA_ATTR_NO_KERNEL_MAPPING mapping, which is clearly forbidden and
   will do the wrong thing on various dma mapping implementations.  The
   fact that dma-direct uses a struct page as a cookie is an undocumented
   implementation detail
 - include dma-map-ops.h and use pgprot_dmacoherent despite a clear
   comment documenting that this is not acceptable
 - use of the VM_DMA_COHERENT for something that is not the dma-mapping
   code
 - use of VM_FLUSH_RESET_PERMS for vmap, while it is only supported for
   vmalloc

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/remoteproc/qcom_q6v5_mss.c | 38 +++++-------------------------
 1 file changed, 6 insertions(+), 32 deletions(-)

diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
index fddb63cffee078..a8b141db4de63f 100644
--- a/drivers/remoteproc/qcom_q6v5_mss.c
+++ b/drivers/remoteproc/qcom_q6v5_mss.c
@@ -10,7 +10,6 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/devcoredump.h>
-#include <linux/dma-map-ops.h>
 #include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
@@ -933,52 +932,27 @@ static void q6v5proc_halt_axi_port(struct q6v5 *qproc,
 static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
 				const char *fw_name)
 {
-	unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS | DMA_ATTR_NO_KERNEL_MAPPING;
-	unsigned long flags = VM_DMA_COHERENT | VM_FLUSH_RESET_PERMS;
-	struct page **pages;
-	struct page *page;
+	unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS;
 	dma_addr_t phys;
 	void *metadata;
 	int mdata_perm;
 	int xferop_ret;
 	size_t size;
-	void *vaddr;
-	int count;
+	void *ptr;
 	int ret;
-	int i;
 
 	metadata = qcom_mdt_read_metadata(fw, &size, fw_name, qproc->dev);
 	if (IS_ERR(metadata))
 		return PTR_ERR(metadata);
 
-	page = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
-	if (!page) {
+	ptr = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
+	if (!ptr) {
 		kfree(metadata);
 		dev_err(qproc->dev, "failed to allocate mdt buffer\n");
 		return -ENOMEM;
 	}
 
-	count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	pages = kmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
-	if (!pages) {
-		ret = -ENOMEM;
-		goto free_dma_attrs;
-	}
-
-	for (i = 0; i < count; i++)
-		pages[i] = nth_page(page, i);
-
-	vaddr = vmap(pages, count, flags, pgprot_dmacoherent(PAGE_KERNEL));
-	kfree(pages);
-	if (!vaddr) {
-		dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n", &phys, size);
-		ret = -EBUSY;
-		goto free_dma_attrs;
-	}
-
-	memcpy(vaddr, metadata, size);
-
-	vunmap(vaddr);
+	memcpy(ptr, metadata, size);
 
 	/* Hypervisor mapping to access metadata by modem */
 	mdata_perm = BIT(QCOM_SCM_VMID_HLOS);
@@ -1008,7 +982,7 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
 			 "mdt buffer not reclaimed system may become unstable\n");
 
 free_dma_attrs:
-	dma_free_attrs(qproc->dev, size, page, phys, dma_attrs);
+	dma_free_attrs(qproc->dev, size, ptr, phys, dma_attrs);
 	kfree(metadata);
 
 	return ret < 0 ? ret : 0;
-- 
2.35.1