Ack. vmovdqa64 is an aligned move [google it...] so it's no surprise whatsoever
that it blew up. If you check the new/improved assembly code, you'll probably
see that the compiler generated a 'u' flavor [unaligned] vector move.
Thanks... Dave
-----Original Message-----
From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Elias Rudberg
Sent: Wednesday, May 6, 2020 7:56 PM
To: dmar...@me.com
Cc: Dave Barach (dbarach) <dbar...@cisco.com>; vpp-dev@lists.fd.io
Subject: Re: [vpp-dev] Segmentation fault in rdma_device_input_refill when
using clang compiler
Hi Dave and Damjan,
Here is instruction and register info:
(gdb) x/i $pc
=> 0x7fffabbbdd67 <rdma_device_input_refill+759>: vmovdqa64
-0x30a0(%rbp),%ymm0
(gdb) info registers rbp ymm0
rbp 0x7ffff417daf0 0x7ffff417daf0
ymm0 {v8_float = {0x0, 0x0, 0x0, 0x3, 0x0, 0x0, 0x0,
0xfffffffd}, v4_double = {0x0, 0x37, 0x0, 0xffffffffffffff85}, v32_int8 = {0x0,
0x0, 0x0, 0x10,
0x3f, 0xf6, 0x41, 0x80, 0x0, 0x0, 0x0, 0x10, 0x3f, 0xf6, 0x4b, 0x40, 0x0,
0x0, 0x0, 0x10, 0x3f, 0xf6, 0x55, 0x0, 0x0, 0x0, 0x0, 0x10, 0x3f, 0xf6, 0x5e,
0xc0}, v16_int16 = {0x0, 0x1000, 0xf63f, 0x8041, 0x0, 0x1000, 0xf63f,
0x404b, 0x0, 0x1000, 0xf63f, 0x55, 0x0, 0x1000, 0xf63f, 0xc05e}, v8_int32 = {
0x10000000, 0x8041f63f, 0x10000000, 0x404bf63f, 0x10000000, 0x55f63f,
0x10000000, 0xc05ef63f}, v4_int64 = {0x8041f63f10000000, 0x404bf63f10000000,
0x55f63f10000000, 0xc05ef63f10000000}, v2_int128 =
{0x404bf63f100000008041f63f10000000,
0xc05ef63f100000000055f63f10000000}}
Not sure if I understand all this but perhaps it means that the value in %rbp
is used as a memory address, but that address 0x7ffff417daf0 is not 32-byte
aligned as it needs to be.
Adding __attribute__((aligned(32))) as Damjan suggests indeed seems to help.
After that there was again a segfault in another place in the same file, where
the same trick of adding __attribute__((aligned(32))) again helped.
So it seems the problem can be fixed by adding that alignment attribute in two
places, like this:
diff --git a/src/plugins/rdma/input.c b/src/plugins/rdma/input.c index
cf0b6bffe..324436f01 100644
--- a/src/plugins/rdma/input.c
+++ b/src/plugins/rdma/input.c
@@ -103,7 +103,7 @@ rdma_device_input_refill (vlib_main_t * vm, rdma_device_t *
rd,
if (is_mlx5dv)
{
- u64 va[8];
+ u64 va[8] __attribute__((aligned(32)));
mlx5dv_rwq_t *wqe = rxq->wqes + slot;
while (n >= 1)
@@ -488,7 +488,7 @@ rdma_device_input_inline (vlib_main_t * vm,
vlib_node_runtime_t * node,
rdma_rxq_t *rxq = vec_elt_at_index (rd->rxqs, qid);
vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
struct ibv_wc wc[VLIB_FRAME_SIZE];
- u32 byte_cnts[VLIB_FRAME_SIZE];
+ u32 byte_cnts[VLIB_FRAME_SIZE] __attribute__((aligned(32)));
vlib_buffer_t bt;
u32 next_index, *to_next, n_left_to_next, n_rx_bytes = 0;
int n_rx_packets, skip_ip4_cksum = 0;
Many thanks for you help!
Should I push the above as a patch to gerrit?
/ Elias
On Wed, 2020-05-06 at 20:38 +0200, Damjan Marion wrote:
> Can you try this:
>
> diff --git a/src/plugins/rdma/input.c b/src/plugins/rdma/input.c index
> cf0b6bffe..b461ee27b 100644
> --- a/src/plugins/rdma/input.c
> +++ b/src/plugins/rdma/input.c
> @@ -103,7 +103,7 @@ rdma_device_input_refill (vlib_main_t * vm,
> rdma_device_t * rd,
>
> if (is_mlx5dv)
> {
> - u64 va[8];
> + u64 va[8] __attribute__((aligned(32)));
> mlx5dv_rwq_t *wqe = rxq->wqes + slot;
>
> while (n >= 1)
>
>
> Thanks!
>
> > On 6 May 2020, at 19:45, Elias Rudberg <elias.rudb...@bahnhof.net>
> > wrote:
> >
> > Hello VPP experts,
> >
> > When trying to use the current master branch, we get a segmentation
> > fault error. Here is what it looks like in gdb:
> >
> > Thread 3 "vpp_wk_0" received signal SIGSEGV, Segmentation fault.
> > [Switching to Thread 0x7fedf91fe700 (LWP 21309)]
> > rdma_device_input_refill (vm=0x7ff8a5d2f4c0, rd=0x7fedd35ed5c0,
> > rxq=0x7ffff7edea80, is_mlx5dv=1)
> > at vpp/src/plugins/rdma/input.c:115
> > 115 *(u64x4 *) (va + 4) = u64x4_byte_swap (*(u64x4 *) (va
> > + 4));
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