Re: [REGRESSION, BISECTED] pci: nvme device with HMB fails on arm64

[Christoph Hellwig <hch@lst.de>]

Hi Liviu,

please try the patch below.  Note that this is in top of mainline,
as the commit you found already needed another fixup, which has
made it to Linus already.

--
From a959cc1a8ee00dcb274922f9d74f6ed632709047 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Fri, 4 Jan 2019 18:31:48 +0100
Subject: dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING for remapped allocations

We need to return a dma_addr_t even if we don't have a kernel mapping.
Do so by consolidating the phys_to_dma call in a single place and jump
to it from all the branches that return successfully.

Fixes: bfd56cd60521 ("dma-mapping: support highmem in the generic remap allocator")
Reported-by: Liviu Dudau <liviu@dudau.co.uk
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/dma/remap.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index 18cc09fc27b9..7a723194ecbe 100644
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -204,8 +204,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		ret = dma_alloc_from_pool(size, &page, flags);
 		if (!ret)
 			return NULL;
-		*dma_handle = phys_to_dma(dev, page_to_phys(page));
-		return ret;
+		goto done;
 	}
 
 	page = __dma_direct_alloc_pages(dev, size, dma_handle, flags, attrs);
@@ -215,8 +214,10 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	/* remove any dirty cache lines on the kernel alias */
 	arch_dma_prep_coherent(page, size);
 
-	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
-		return page; /* opaque cookie */
+	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING) {
+		ret = page; /* opaque cookie */
+		goto done;
+	}
 
 	/* create a coherent mapping */
 	ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
@@ -227,9 +228,9 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		return ret;
 	}
 
-	*dma_handle = phys_to_dma(dev, page_to_phys(page));
 	memset(ret, 0, size);
-
+done:
+	*dma_handle = phys_to_dma(dev, page_to_phys(page));
 	return ret;
 }
 
-- 
2.20.1