Re: [PATCH 3/4] dma-mapping: introduce a dma_common_find_pages helper
From: Robin Murphy
Date: Wed Oct 02 2019 - 12:45:41 EST
On 02/10/2019 13:05, Geert Uytterhoeven wrote:
Hi Christoph,
On Fri, Aug 30, 2019 at 8:30 AM Christoph Hellwig <hch@xxxxxx> wrote:
A helper to find the backing page array based on a virtual address.
This also ensures we do the same vm_flags check everywhere instead
of slightly different or missing ones in a few places.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
This is now commit 5cf4537975bbd569 ("dma-mapping: introduce a
dma_common_find_pages helper") in v5.4-rc1, and causes the following
warning during s2ram on r8a7740/armadillo, r7s72100/rskrza1, and
r7s9210/rza2mevb:
sh-eth e9a00000.ethernet eth0: Link is Down
+------------[ cut here ]------------
+WARNING: CPU: 0 PID: 556 at kernel/dma/remap.c:93
remap_allocator_free+0x20/0x30
+trying to free invalid coherent area: 6909579a
+Modules linked in:
+CPU: 0 PID: 556 Comm: s2ram Not tainted
5.3.0-rc6-armadillo-00027-g5cf4537975bbd569-dirty #113
+Hardware name: Generic R8A7740 (Flattened Device Tree)
+[<c010d4b8>] (unwind_backtrace) from [<c010b4d0>] (show_stack+0x10/0x14)
+[<c010b4d0>] (show_stack) from [<c011d978>] (__warn+0xec/0x104)
+[<c011d978>] (__warn) from [<c011d9d4>] (warn_slowpath_fmt+0x44/0x6c)
+[<c011d9d4>] (warn_slowpath_fmt) from [<c011123c>]
(remap_allocator_free+0x20/0x30)
+[<c011123c>] (remap_allocator_free) from [<c0111cc4>]
(__arm_dma_free.constprop.2+0x114/0x144)
+[<c0111cc4>] (__arm_dma_free.constprop.2) from [<c03f193c>]
(sh_eth_ring_free+0xb8/0x114)
+[<c03f193c>] (sh_eth_ring_free) from [<c03f1a00>] (sh_eth_close+0x68/0x8c)
+[<c03f1a00>] (sh_eth_close) from [<c03f1f6c>] (sh_eth_resume+0x44/0x90)
+[<c03f1f6c>] (sh_eth_resume) from [<c03b7d3c>] (dpm_run_callback+0x64/0xdc)
+[<c03b7d3c>] (dpm_run_callback) from [<c03b80c0>]
(device_resume+0xbc/0x180)
+[<c03b80c0>] (device_resume) from [<c03b89b0>] (dpm_resume+0x124/0x1b0)
+[<c03b89b0>] (dpm_resume) from [<c03b8c5c>] (dpm_resume_end+0xc/0x18)
+[<c03b8c5c>] (dpm_resume_end) from [<c0158d2c>]
(suspend_devices_and_enter+0x15c/0x5ac)
+[<c0158d2c>] (suspend_devices_and_enter) from [<c01593bc>]
(pm_suspend+0x240/0x2f4)
+[<c01593bc>] (pm_suspend) from [<c0157b48>] (state_store+0x54/0x8c)
+[<c0157b48>] (state_store) from [<c0276ecc>] (kernfs_fop_write+0x154/0x1c8)
+[<c0276ecc>] (kernfs_fop_write) from [<c0209f74>] (__vfs_write+0x28/0xe0)
+[<c0209f74>] (__vfs_write) from [<c020acc0>] (vfs_write+0x98/0xbc)
+[<c020acc0>] (vfs_write) from [<c020ae48>] (ksys_write+0x68/0xb4)
+[<c020ae48>] (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
+Exception stack(0xdd74dfa8 to 0xdd74dff0)
+dfa0: 00000004 000e2408 00000001 000e2408
00000004 00000000
+dfc0: 00000004 000e2408 b6f36d60 00000004 000e2408 00000004
00000000 00000000
+dfe0: 00000000 be9fc74c b6e991bb b6ed5af6
+irq event stamp: 0
+hardirqs last enabled at (0): [<00000000>] 0x0
+hardirqs last disabled at (0): [<c011b73c>] copy_process+0x520/0x14b8
+softirqs last enabled at (0): [<c011b73c>] copy_process+0x520/0x14b8
+softirqs last disabled at (0): [<00000000>] 0x0
+---[ end trace 22461a068edbf2c1 ]---
+------------[ cut here ]------------
+WARNING: CPU: 0 PID: 556 at kernel/dma/remap.c:93
remap_allocator_free+0x20/0x30
+trying to free invalid coherent area: f39c52ba
[...]
+---[ end trace 22461a068edbf2c2 ]---
SMSC LAN8710/LAN8720 e9a00000.ethernet-ffffffff:00: attached PHY
driver [SMSC LAN8710/LAN8720]
(mii_bus:phy_addr=e9a00000.ethernet-ffffffff:00, irq=POLL)
(the dirty is due to the need for "ARM: fix __get_user_check() in case
uaccess_* calls are not inlined").
BTW, I cannot trigger the issue on r8a7791/koelsch, which also uses
sh-eth, not even when disabling CONFIG_IOMMU_SUPPORT and CONFIG_ARM_LPAE
(both are not set for the affected platforms).
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -541,15 +541,6 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
return pages;
}
-static struct page **__iommu_dma_get_pages(void *cpu_addr)
-{
- struct vm_struct *area = find_vm_area(cpu_addr);
-
- if (!area || !area->pages)
This checks area->pages...
32-bit Arm doesn't use iommu-dma, so I don't see how this could be
relevant to the reported problem, but either way this "check" of
area->pages...
- return NULL;
- return area->pages;
-}
-
/**
* iommu_dma_alloc_remap - Allocate and map a buffer contiguous in IOVA space
* @dev: Device to allocate memory for. Must be a real device
@@ -938,7 +929,7 @@ static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
* If it the address is remapped, then it's either non-coherent
* or highmem CMA, or an iommu_dma_alloc_remap() construction.
*/
- pages = __iommu_dma_get_pages(cpu_addr);
+ pages = dma_common_find_pages(cpu_addr);
if (!pages)
page = vmalloc_to_page(cpu_addr);
dma_common_free_remap(cpu_addr, alloc_size);
@@ -1045,7 +1036,7 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
return -ENXIO;
if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
- struct page **pages = __iommu_dma_get_pages(cpu_addr);
+ struct page **pages = dma_common_find_pages(cpu_addr);
if (pages)
return __iommu_dma_mmap(pages, size, vma);
@@ -1067,7 +1058,7 @@ static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
int ret;
if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
- struct page **pages = __iommu_dma_get_pages(cpu_addr);
+ struct page **pages = dma_common_find_pages(cpu_addr);
if (pages) {
return sg_alloc_table_from_pages(sgt, pages,
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -11,6 +11,15 @@
#include <linux/slab.h>
#include <linux/vmalloc.h>
+struct page **dma_common_find_pages(void *cpu_addr)
+{
+ struct vm_struct *area = find_vm_area(cpu_addr);
+
+ if (!area || area->flags != VM_DMA_COHERENT)
... while this one checks area->flags?
+ return NULL;
+ return area->pages;
...remains inherent in this statement ;)
Introducing the additional area->flags check is rather the point of the
patch. As to how it could affect the behaviour of
remap_allocator_{alloc,free}(), that probably warrants some more digging
in the arch/arm code. Having looked briefly to see if anything jumped
out, I do notice that for the dma_common_contiguous_remap() case we're
now relying on a dangling pointer to a long-gone kernel stack in
area->pages to pass the check in dma_common_free_remap() - I can't see
that that has any bearing on the reported issue, but it is a bit icky.
Robin.
+}
+
static struct vm_struct *__dma_common_pages_remap(struct page **pages,
size_t size, pgprot_t prot, const void *caller)
{
Gr{oetje,eeting}s,
Geert