* [PATCH net v3 0/2] sfc: Restrict PIO for 64bit arch in order to avoid data corruption
@ 2014-05-29 10:18 Shradha Shah
2014-05-29 10:20 ` [PATCH net v3 1/2] sfc: use 64-bit writes for PIO Shradha Shah
2014-05-29 10:20 ` [PATCH net v3 2/2] sfc: Restrict PIO to 64-bit architectures Shradha Shah
0 siblings, 2 replies; 4+ messages in thread
From: Shradha Shah @ 2014-05-29 10:18 UTC (permalink / raw)
To: David Miller; +Cc: netdev, linux-net-drivers
This patch series
Fixes: ee45fd92c739("sfc: Use TX PIO for sufficiently small packets")
The linux net driver uses memcpy_toio() in order to copy into
the PIO buffers.
Even on a 64bit machine this causes 32bit accesses to a write-
combined memory region.
There are hardware limitations that mean that only
64bit naturally aligned accesses are safe in all cases. Due to being
write-combined memory region two 32bit accesses may be coalesced to
form a 64bit non 64bit aligned access.
Solution was to open-code the memory copy routines using pointers
and to only enable PIO for x86_64 machines.
This bug fix applies to v3.13 and v3.14 stable branches.
Jon Cooper (2):
sfc: use 64-bit writes for PIO.
sfc: Restrict PIO to 64-bit architectures
drivers/net/ethernet/sfc/io.h | 8 ++++++++
drivers/net/ethernet/sfc/tx.c | 24 +++++++++++++++++++-----
2 files changed, 27 insertions(+), 5 deletions(-)
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH net v3 1/2] sfc: use 64-bit writes for PIO.
2014-05-29 10:18 [PATCH net v3 0/2] sfc: Restrict PIO for 64bit arch in order to avoid data corruption Shradha Shah
@ 2014-05-29 10:20 ` Shradha Shah
2014-06-02 5:25 ` David Miller
2014-05-29 10:20 ` [PATCH net v3 2/2] sfc: Restrict PIO to 64-bit architectures Shradha Shah
1 sibling, 1 reply; 4+ messages in thread
From: Shradha Shah @ 2014-05-29 10:20 UTC (permalink / raw)
To: David Miller; +Cc: netdev, linux-net-drivers
From: Jon Cooper <jcooper@solarflare.com>
Patch to open-code the memory copy routines.
32bit writes over the PCI bus causes data corruption.
Fixes:ee45fd92c739
("sfc: Use TX PIO for sufficiently small packets")
Signed-off-by: Shradha Shah <sshah@solarflare.com>
---
drivers/net/ethernet/sfc/tx.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
index fa94753..031e751 100644
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -189,6 +189,20 @@ struct efx_short_copy_buffer {
u8 buf[L1_CACHE_BYTES];
};
+/* Copy in explicit 64-bit writes. */
+static void efx_memcpy_64(void *dest, void *src, size_t len)
+{
+ uint64_t *src64 = src, *dest64 = dest;
+ size_t i, l64 = len / 8;
+
+ WARN_ON_ONCE(len % 8 != 0);
+ WARN_ON_ONCE(((u8 *)dest - (u8 *)0) % 8 != 0);
+ BUILD_BUG_ON(sizeof(uint64_t) != 8);
+
+ for(i = 0; i < l64; ++i)
+ dest64[i] = src64[i];
+}
+
/* Copy to PIO, respecting that writes to PIO buffers must be dword aligned.
* Advances piobuf pointer. Leaves additional data in the copy buffer.
*/
@@ -198,7 +212,7 @@ static void efx_memcpy_toio_aligned(struct efx_nic *efx, u8 __iomem **piobuf,
{
int block_len = len & ~(sizeof(copy_buf->buf) - 1);
- memcpy_toio(*piobuf, data, block_len);
+ efx_memcpy_64(*piobuf, data, block_len);
*piobuf += block_len;
len -= block_len;
@@ -230,7 +244,7 @@ static void efx_memcpy_toio_aligned_cb(struct efx_nic *efx, u8 __iomem **piobuf,
if (copy_buf->used < sizeof(copy_buf->buf))
return;
- memcpy_toio(*piobuf, copy_buf->buf, sizeof(copy_buf->buf));
+ efx_memcpy_64(*piobuf, copy_buf->buf, sizeof(copy_buf->buf));
*piobuf += sizeof(copy_buf->buf);
data += copy_to_buf;
len -= copy_to_buf;
@@ -245,7 +259,7 @@ static void efx_flush_copy_buffer(struct efx_nic *efx, u8 __iomem *piobuf,
{
/* if there's anything in it, write the whole buffer, including junk */
if (copy_buf->used)
- memcpy_toio(piobuf, copy_buf->buf, sizeof(copy_buf->buf));
+ efx_memcpy_64(piobuf, copy_buf->buf, sizeof(copy_buf->buf));
}
/* Traverse skb structure and copy fragments in to PIO buffer.
@@ -304,8 +318,8 @@ efx_enqueue_skb_pio(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
*/
BUILD_BUG_ON(L1_CACHE_BYTES >
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
- memcpy_toio(tx_queue->piobuf, skb->data,
- ALIGN(skb->len, L1_CACHE_BYTES));
+ efx_memcpy_64(tx_queue->piobuf, skb->data,
+ ALIGN(skb->len, L1_CACHE_BYTES));
}
EFX_POPULATE_QWORD_5(buffer->option,
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH net v3 2/2] sfc: Restrict PIO to 64-bit architectures
2014-05-29 10:18 [PATCH net v3 0/2] sfc: Restrict PIO for 64bit arch in order to avoid data corruption Shradha Shah
2014-05-29 10:20 ` [PATCH net v3 1/2] sfc: use 64-bit writes for PIO Shradha Shah
@ 2014-05-29 10:20 ` Shradha Shah
1 sibling, 0 replies; 4+ messages in thread
From: Shradha Shah @ 2014-05-29 10:20 UTC (permalink / raw)
To: David Miller; +Cc: netdev, linux-net-drivers
From: Jon Cooper <jcooper@solarflare.com>
Enable PIO for x86_64 architecture only.
Not tested on platforms other than x86_64.
Fixes:ee45fd92c739
("sfc: Use TX PIO for sufficiently small packets")
Signed-off-by: Shradha Shah <sshah@solarflare.com>
---
drivers/net/ethernet/sfc/io.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/net/ethernet/sfc/io.h b/drivers/net/ethernet/sfc/io.h
index 4d3f119..adadcf0 100644
--- a/drivers/net/ethernet/sfc/io.h
+++ b/drivers/net/ethernet/sfc/io.h
@@ -66,10 +66,18 @@
#define EFX_USE_QWORD_IO 1
#endif
+/* PIO only works on 64-bit architectures */
+#if BITS_PER_LONG == 64
+/* not strictly necessary to restrict to x86 arch, but done for safety
+ * since unusual write combining behaviour can break PIO.
+ */
+#ifdef CONFIG_X86_64
/* PIO is a win only if write-combining is possible */
#ifdef ARCH_HAS_IOREMAP_WC
#define EFX_USE_PIO 1
#endif
+#endif
+#endif
#ifdef EFX_USE_QWORD_IO
static inline void _efx_writeq(struct efx_nic *efx, __le64 value,
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net v3 1/2] sfc: use 64-bit writes for PIO.
2014-05-29 10:20 ` [PATCH net v3 1/2] sfc: use 64-bit writes for PIO Shradha Shah
@ 2014-06-02 5:25 ` David Miller
0 siblings, 0 replies; 4+ messages in thread
From: David Miller @ 2014-06-02 5:25 UTC (permalink / raw)
To: sshah; +Cc: netdev, linux-net-drivers
From: Shradha Shah <sshah@solarflare.com>
Date: Thu, 29 May 2014 11:20:22 +0100
> +/* Copy in explicit 64-bit writes. */
> +static void efx_memcpy_64(void *dest, void *src, size_t len)
> +{
> + uint64_t *src64 = src, *dest64 = dest;
> + size_t i, l64 = len / 8;
> +
> + WARN_ON_ONCE(len % 8 != 0);
> + WARN_ON_ONCE(((u8 *)dest - (u8 *)0) % 8 != 0);
> + BUILD_BUG_ON(sizeof(uint64_t) != 8);
> +
> + for(i = 0; i < l64; ++i)
> + dest64[i] = src64[i];
> +}
You absolutely, positively, cannot do this.
I/O memory pointers aren't pointers, they are opaque addresses, sparse
should have given you a loud warning about this.
On some platforms they are physical addresses, or some other special
value.
Therefore you cannot directly dereference them.
You _must_ use the io.h accessors.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-06-02 5:25 UTC | newest]
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2014-05-29 10:18 [PATCH net v3 0/2] sfc: Restrict PIO for 64bit arch in order to avoid data corruption Shradha Shah
2014-05-29 10:20 ` [PATCH net v3 1/2] sfc: use 64-bit writes for PIO Shradha Shah
2014-06-02 5:25 ` David Miller
2014-05-29 10:20 ` [PATCH net v3 2/2] sfc: Restrict PIO to 64-bit architectures Shradha Shah
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