Re: swiotlb/caamjr regression (Was: [GIT PULL] (swiotlb) stable/for-linus-5.12)

On Fri, Jun 11, 2021 at 08:21:53AM +0200, Christoph Hellwig wrote:

On Thu, Jun 10, 2021 at 05:52:07PM +0300, Horia Geantă wrote:

quoted

I've noticed the failure also in v5.10 and v5.11 stable kernels,
since the patch set has been backported.

FYI, there has been a patch on the list that should have fixed this
for about a month:

https://lore.kernel.org/linux-iommu/20210510091816.GA2084@lst.de/T/#m0d0df6490350a08dcc24c9086c8edc165b402d6f (local)

but it seems like it never got picked up.

Yikes!

Dominique,

Would you be up to testing the attached (and inline) patch please?

Linus,

Would you be terribly offended if I took your code (s/unsigned
long/unsigned int), and used Chanho's description of the problem (see below)?

Christoph,
I took the liberty of putting your Reviewed-by on the patch, you OK with
that?

Jianxiong,
Would you be up for testing this patch on your NVMe rig please? I don't
forsee a problem.. but just in case

From f06da55596675383fbf2563fe2919b2a8f68901b Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 10 Jun 2021 12:41:26 -0700
Subject: [PATCH] swiotlb: manipulate orig_addr when tlb_addr has offset
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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.]

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

[This patch text is from Bumyong's email; and his solution was very close
to Linus's, so incorporating his text]

Fixes: 16fc3cef33a0 ("swiotlb: don't modify orig_addr in swiotlb_tbl_sync_single")
Signed-off-by: Bumyong Lee <redacted>
Signed-off-by: Chanho Park <redacted>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reported-by: Dominique MARTINET <redacted>
Reported-by: Horia Geantă <horia.geanta@nxp.com>
Tested-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CC: <redacted>
Signed-off-by: Konrad Rzeszutek Wilk <redacted>
---
 kernel/dma/swiotlb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 8ca7d50..dc438b5 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c

@@ -342,6 +342,7 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
 {
 	struct io_tlb_mem *mem = io_tlb_default_mem;
 	int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
+	unsigned int offset = (tlb_addr - mem->start) & (IO_TLB_SIZE - 1);
 	phys_addr_t orig_addr = mem->slots[index].orig_addr;
 	size_t alloc_size = mem->slots[index].alloc_size;
 	unsigned long pfn = PFN_DOWN(orig_addr);

@@ -350,6 +351,14 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
 	if (orig_addr == INVALID_PHYS_ADDR)
 		return;
 
+	if (offset > alloc_size) {
+		dev_WARN_ONCE(dev, 1,
+			"Buffer overflow detected. Offset: %lu. Mapping size: %zu.\n",
+			offset, size);
+		return;
+	}
+	alloc_size -= offset;
+	orig_addr += offset;
 	if (size > alloc_size) {
 		dev_WARN_ONCE(dev, 1,
 			"Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",

-- 
1.8.3.1