lkml.org 
[lkml]   [2021]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5.12 102/110] swiotlb: manipulate orig_addr when tlb_addr has offset
Date
From: Bumyong Lee <bumyong.lee@samsung.com>

commit 5f89468e2f060031cd89fd4287298e0eaf246bf6 upstream.

in case of driver wants to sync part of ranges with offset,
swiotlb_tbl_sync_single() copies from orig_addr base to tlb_addr with
offset and ends up with data mismatch.

It was removed from
"swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single",
but said logic has to be added back in.

From Linus's email:
"That commit which the removed the offset calculation entirely, because the old

(unsigned long)tlb_addr & (IO_TLB_SIZE - 1)

was wrong, but instead of removing it, I think it should have just
fixed it to be

(tlb_addr - mem->start) & (IO_TLB_SIZE - 1);

instead. That way the slot offset always matches the slot index calculation."

(Unfortunatly that broke NVMe).

The use-case that drivers are hitting is as follow:

1. Get dma_addr_t from dma_map_single()

dma_addr_t tlb_addr = dma_map_single(dev, vaddr, vsize, DMA_TO_DEVICE);

|<---------------vsize------------->|
+-----------------------------------+
| | original buffer
+-----------------------------------+
vaddr

swiotlb_align_offset
|<----->|<---------------vsize------------->|
+-------+-----------------------------------+
| | | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

2. Do something
3. Sync dma_addr_t through dma_sync_single_for_device(..)

dma_sync_single_for_device(dev, tlb_addr + offset, size, DMA_TO_DEVICE);

Error case.
Copy data to original buffer but it is from base addr (instead of
base addr + offset) in original buffer:

swiotlb_align_offset
|<----->|<- offset ->|<- size ->|
+-------+-----------------------------------+
| | |##########| | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

|<- size ->|
+-----------------------------------+
|##########| | original buffer
+-----------------------------------+
vaddr

The fix is to copy the data to the original buffer and take into
account the offset, like so:

swiotlb_align_offset
|<----->|<- offset ->|<- size ->|
+-------+-----------------------------------+
| | |##########| | swiotlb buffer
+-------+-----------------------------------+
tlb_addr

|<- offset ->|<- size ->|
+-----------------------------------+
| |##########| | original buffer
+-----------------------------------+
vaddr

[One fix which was Linus's that made more sense to as it created a
symmetry would break NVMe. The reason for that is the:
unsigned int offset = (tlb_addr - mem->start) & (IO_TLB_SIZE - 1);

would come up with the proper offset, but it would lose the
alignment (which this patch contains).]

Fixes: 16fc3cef33a0 ("swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single")
Signed-off-by: Bumyong Lee <bumyong.lee@samsung.com>
Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reported-by: Dominique MARTINET <dominique.martinet@atmark-techno.com>
Reported-by: Horia Geantă <horia.geanta@nxp.com>
Tested-by: Horia Geantă <horia.geanta@nxp.com>
CC: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/dma/swiotlb.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index fe4c01c14ab2..e96f3808e431 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -724,11 +724,17 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
size_t orig_size = io_tlb_orig_size[index];
phys_addr_t orig_addr = io_tlb_orig_addr[index];
+ unsigned int tlb_offset;

if (orig_addr == INVALID_PHYS_ADDR)
return;

- validate_sync_size_and_truncate(hwdev, orig_size, &size);
+ tlb_offset = (tlb_addr & (IO_TLB_SIZE - 1)) -
+ swiotlb_align_offset(hwdev, orig_addr);
+
+ orig_addr += tlb_offset;
+
+ validate_sync_size_and_truncate(hwdev, orig_size - tlb_offset, &size);

switch (target) {
case SYNC_FOR_CPU:
--
2.30.2
\
 
 \ /
  Last update: 2021-06-28 16:29    [W:0.444 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site