[PATCH 06/13] IB/hfi1: Do not read more than a SGE length

Dennis Dalessandro
2016-09-25T14:41:32Z

From: Sebastian Sanchez <sebastian.sanchez-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

In certain cases, if the tail of an SGE is not
8-byte aligned, bytes beyond the end to an 8-byte
alignment can be read. Change the copy routine
to avoid the over-read. Instead, stop on the final
whole quad-word, then read the remaining bytes.

Reviewed-by: Dean Luick <dean.luick-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Sebastian Sanchez <sebastian.sanchez-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
drivers/infiniband/hw/hfi1/pio_copy.c | 88 +++++++++++++++------------------
1 files changed, 40 insertions(+), 48 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/pio_copy.c b/drivers/infiniband/hw/hfi1/pio_copy.c
index 3a1ef30..7b0aa19 100644
--- a/drivers/infiniband/hw/hfi1/pio_copy.c
+++ b/drivers/infiniband/hw/hfi1/pio_copy.c
@@ -254,30 +254,6 @@ static inline void read_extra_bytes(struct pio_buf *pbuf,
}

/*
- * Zero extra bytes from the end of pbuf->carry.
- *
- * NOTES:
- * o zbytes <= old_bytes
- */
-static inline void zero_extra_bytes(struct pio_buf *pbuf, unsigned int zbytes)
-{
- unsigned int remaining;
-
- if (zbytes == 0) /* nothing to do */
- return;
-
- remaining = pbuf->carry_bytes - zbytes; /* remaining bytes */
-
- /* NOTE: zshift only guaranteed to work if remaining != 0 */
- if (remaining)
- pbuf->carry.val64 = (pbuf->carry.val64 << zshift(remaining))
- >> zshift(remaining);
- else
- pbuf->carry.val64 = 0;
- pbuf->carry_bytes = remaining;
-}
-
-/*
* Write a quad word using parts of pbuf->carry and the next 8 bytes of src.
* Put the unused part of the next 8 bytes of src into the LSB bytes of
* pbuf->carry with the upper bytes zeroed..
@@ -385,20 +361,6 @@ static inline void read_extra_bytes(struct pio_buf *pbuf,
}

/*
- * Zero extra bytes from the end of pbuf->carry.
- *
- * We do not care about the value of unused bytes in carry, so just
- * reduce the byte count.
- *
- * NOTES:
- * o zbytes <= old_bytes
- */
-static inline void zero_extra_bytes(struct pio_buf *pbuf, unsigned int zbytes)
-{
- pbuf->carry_bytes -= zbytes;
-}
-
-/*
* Write a quad word using parts of pbuf->carry and the next 8 bytes of src.
* Put the unused part of the next 8 bytes of src into the low bytes of
* pbuf->carry.
@@ -550,8 +512,8 @@ static void mid_copy_mix(struct pio_buf *pbuf, const void *from, size_t nbytes)
{
void __iomem *dest = pbuf->start + (pbuf->qw_written * sizeof(u64));
void __iomem *dend; /* 8-byte data end */
- unsigned long qw_to_write = (pbuf->carry_bytes + nbytes) >> 3;
- unsigned long bytes_left = (pbuf->carry_bytes + nbytes) & 0x7;
+ unsigned long qw_to_write = nbytes >> 3;
+ unsigned long bytes_left = nbytes & 0x7;

/* calculate 8-byte data end */
dend = dest + (qw_to_write * sizeof(u64));
@@ -621,16 +583,46 @@ static void mid_copy_mix(struct pio_buf *pbuf, const void *from, size_t nbytes)
dest += sizeof(u64);
}

- /* adjust carry */
- if (pbuf->carry_bytes < bytes_left) {
- /* need to read more */
- read_extra_bytes(pbuf, from, bytes_left - pbuf->carry_bytes);
+ pbuf->qw_written += qw_to_write;
+
+ /* handle carry and left-over bytes */
+ if (pbuf->carry_bytes + bytes_left >= 8) {
+ unsigned long nread;
+
+ /* there is enough to fill another qw - fill carry */
+ nread = 8 - pbuf->carry_bytes;
+ read_extra_bytes(pbuf, from, nread);
+
+ /*
+ * One more write - but need to make sure dest is correct.
+ * Check for wrap and the possibility the write
+ * should be in SOP space.
+ *
+ * The two checks immediately below cannot both be true, hence
+ * the else. If we have wrapped, we cannot still be within the
+ * first block. Conversely, if we are still in the first block,
+ * we cannot have wrapped. We do the wrap check first as that
+ * is more likely.
+ */
+ /* adjust if we have wrapped */
+ if (dest >= pbuf->end)
+ dest -= pbuf->size;
+ /* jump to the SOP range if within the first block */
+ else if (pbuf->qw_written < PIO_BLOCK_QWS)
+ dest += SOP_DISTANCE;
+
+ /* flush out full carry */
+ carry8_write8(pbuf->carry, dest);
+ pbuf->qw_written++;
+
+ /* now adjust and read the rest of the bytes into carry */
+ bytes_left -= nread;
+ from += nread; /* from is now not aligned */
+ read_low_bytes(pbuf, from, bytes_left);
} else {
- /* remove invalid bytes */
- zero_extra_bytes(pbuf, pbuf->carry_bytes - bytes_left);
+ /* not enough to fill another qw, append the rest to carry */
+ read_extra_bytes(pbuf, from, bytes_left);
}
-
- pbuf->qw_written += qw_to_write;
}