* [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model
@ 2021-03-29 8:00 Ong Boon Leong
2021-03-29 15:02 ` Jesper Dangaard Brouer
0 siblings, 1 reply; 5+ messages in thread
From: Ong Boon Leong @ 2021-03-29 8:00 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, David S . Miller,
Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend,
Toshiaki Makita
Cc: netdev, bpf, linux-kernel, Ong Boon Leong
xdp_return_frame() may be called outside of NAPI context to return
xdpf back to page_pool. xdp_return_frame() calls __xdp_return() with
napi_direct = false. For page_pool memory model, __xdp_return() calls
xdp_return_frame_no_direct() unconditionally and below false negative
kernel BUG throw happened under preempt-rt build:
[ 430.450355] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/3884
[ 430.451678] caller is __xdp_return+0x1ff/0x2e0
[ 430.452111] CPU: 0 PID: 3884 Comm: modprobe Tainted: G U E 5.12.0-rc2+ #45
So, this patch fixes the issue by adding "if (napi_direct)" condition
to skip calling xdp_return_frame_no_direct() if napi_direct = false.
Fixes: 2539650fadbf ("xdp: Helpers for disabling napi_direct of xdp_return_frame")
Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
---
net/core/xdp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 05354976c1fc..4eaa28972af2 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -350,7 +350,8 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
/* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
page = virt_to_head_page(data);
- napi_direct &= !xdp_return_frame_no_direct();
+ if (napi_direct)
+ napi_direct &= !xdp_return_frame_no_direct();
page_pool_put_full_page(xa->page_pool, page, napi_direct);
rcu_read_unlock();
break;
--
2.25.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model
2021-03-29 8:00 [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model Ong Boon Leong
@ 2021-03-29 15:02 ` Jesper Dangaard Brouer
2021-03-29 16:25 ` Toke Høiland-Jørgensen
2021-03-31 12:59 ` Ong, Boon Leong
0 siblings, 2 replies; 5+ messages in thread
From: Jesper Dangaard Brouer @ 2021-03-29 15:02 UTC (permalink / raw)
To: Ong Boon Leong
Cc: brouer, Alexei Starovoitov, Daniel Borkmann, David S . Miller,
Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend,
Toshiaki Makita, netdev, bpf, linux-kernel
On Mon, 29 Mar 2021 16:00:39 +0800
Ong Boon Leong <boon.leong.ong@intel.com> wrote:
> xdp_return_frame() may be called outside of NAPI context to return
> xdpf back to page_pool. xdp_return_frame() calls __xdp_return() with
> napi_direct = false. For page_pool memory model, __xdp_return() calls
> xdp_return_frame_no_direct() unconditionally and below false negative
> kernel BUG throw happened under preempt-rt build:
>
> [ 430.450355] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/3884
> [ 430.451678] caller is __xdp_return+0x1ff/0x2e0
> [ 430.452111] CPU: 0 PID: 3884 Comm: modprobe Tainted: G U E 5.12.0-rc2+ #45
>
> So, this patch fixes the issue by adding "if (napi_direct)" condition
> to skip calling xdp_return_frame_no_direct() if napi_direct = false.
>
> Fixes: 2539650fadbf ("xdp: Helpers for disabling napi_direct of xdp_return_frame")
> Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
> ---
This looks correct to me.
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
> net/core/xdp.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index 05354976c1fc..4eaa28972af2 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -350,7 +350,8 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
> /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
> xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
> page = virt_to_head_page(data);
> - napi_direct &= !xdp_return_frame_no_direct();
> + if (napi_direct)
> + napi_direct &= !xdp_return_frame_no_direct();
if (napi_direct && xdp_return_frame_no_direct())
napi_direct = false;
I wonder if this code would be easier to understand?
> page_pool_put_full_page(xa->page_pool, page, napi_direct);
> rcu_read_unlock();
> break;
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model
2021-03-29 15:02 ` Jesper Dangaard Brouer
@ 2021-03-29 16:25 ` Toke Høiland-Jørgensen
2021-03-31 8:53 ` Jesper Dangaard Brouer
2021-03-31 12:59 ` Ong, Boon Leong
1 sibling, 1 reply; 5+ messages in thread
From: Toke Høiland-Jørgensen @ 2021-03-29 16:25 UTC (permalink / raw)
To: Jesper Dangaard Brouer, Ong Boon Leong
Cc: brouer, Alexei Starovoitov, Daniel Borkmann, David S . Miller,
Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend,
Toshiaki Makita, netdev, bpf, linux-kernel
Jesper Dangaard Brouer <brouer@redhat.com> writes:
> On Mon, 29 Mar 2021 16:00:39 +0800
> Ong Boon Leong <boon.leong.ong@intel.com> wrote:
>
>> xdp_return_frame() may be called outside of NAPI context to return
>> xdpf back to page_pool. xdp_return_frame() calls __xdp_return() with
>> napi_direct = false. For page_pool memory model, __xdp_return() calls
>> xdp_return_frame_no_direct() unconditionally and below false negative
>> kernel BUG throw happened under preempt-rt build:
>>
>> [ 430.450355] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/3884
>> [ 430.451678] caller is __xdp_return+0x1ff/0x2e0
>> [ 430.452111] CPU: 0 PID: 3884 Comm: modprobe Tainted: G U E 5.12.0-rc2+ #45
>>
>> So, this patch fixes the issue by adding "if (napi_direct)" condition
>> to skip calling xdp_return_frame_no_direct() if napi_direct = false.
>>
>> Fixes: 2539650fadbf ("xdp: Helpers for disabling napi_direct of xdp_return_frame")
>> Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
>> ---
>
> This looks correct to me.
>
> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
>
>
>> net/core/xdp.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/core/xdp.c b/net/core/xdp.c
>> index 05354976c1fc..4eaa28972af2 100644
>> --- a/net/core/xdp.c
>> +++ b/net/core/xdp.c
>> @@ -350,7 +350,8 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
>> /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
>> xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
>> page = virt_to_head_page(data);
>> - napi_direct &= !xdp_return_frame_no_direct();
>> + if (napi_direct)
>> + napi_direct &= !xdp_return_frame_no_direct();
>
> if (napi_direct && xdp_return_frame_no_direct())
> napi_direct = false;
>
> I wonder if this code would be easier to understand?
Yes, IMO it would! :)
-Toke
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model
2021-03-29 16:25 ` Toke Høiland-Jørgensen
@ 2021-03-31 8:53 ` Jesper Dangaard Brouer
0 siblings, 0 replies; 5+ messages in thread
From: Jesper Dangaard Brouer @ 2021-03-31 8:53 UTC (permalink / raw)
To: Toke Høiland-Jørgensen
Cc: Ong Boon Leong, Alexei Starovoitov, Daniel Borkmann,
David S . Miller, Jakub Kicinski, Jesper Dangaard Brouer,
John Fastabend, Toshiaki Makita, netdev, bpf, brouer
Hi Ong,
Patch is in "Changes Requested".
Thus, please send a V2 patch with suggested code changes below.
--Jesper
On Mon, 29 Mar 2021 18:25:08 +0200
Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> Jesper Dangaard Brouer <brouer@redhat.com> writes:
>
> > On Mon, 29 Mar 2021 16:00:39 +0800
> > Ong Boon Leong <boon.leong.ong@intel.com> wrote:
> >
> >> xdp_return_frame() may be called outside of NAPI context to return
> >> xdpf back to page_pool. xdp_return_frame() calls __xdp_return() with
> >> napi_direct = false. For page_pool memory model, __xdp_return() calls
> >> xdp_return_frame_no_direct() unconditionally and below false negative
> >> kernel BUG throw happened under preempt-rt build:
> >>
> >> [ 430.450355] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/3884
> >> [ 430.451678] caller is __xdp_return+0x1ff/0x2e0
> >> [ 430.452111] CPU: 0 PID: 3884 Comm: modprobe Tainted: G U E 5.12.0-rc2+ #45
> >>
> >> So, this patch fixes the issue by adding "if (napi_direct)" condition
> >> to skip calling xdp_return_frame_no_direct() if napi_direct = false.
> >>
> >> Fixes: 2539650fadbf ("xdp: Helpers for disabling napi_direct of xdp_return_frame")
> >> Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
> >> ---
> >
> > This looks correct to me.
> >
> > Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
> >
> >
> >> net/core/xdp.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/net/core/xdp.c b/net/core/xdp.c
> >> index 05354976c1fc..4eaa28972af2 100644
> >> --- a/net/core/xdp.c
> >> +++ b/net/core/xdp.c
> >> @@ -350,7 +350,8 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
> >> /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
> >> xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
> >> page = virt_to_head_page(data);
> >> - napi_direct &= !xdp_return_frame_no_direct();
> >> + if (napi_direct)
> >> + napi_direct &= !xdp_return_frame_no_direct();
> >
> > if (napi_direct && xdp_return_frame_no_direct())
> > napi_direct = false;
> >
> > I wonder if this code would be easier to understand?
>
> Yes, IMO it would! :)
>
> -Toke
>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
^ permalink raw reply [flat|nested] 5+ messages in thread
* RE: [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model
2021-03-29 15:02 ` Jesper Dangaard Brouer
2021-03-29 16:25 ` Toke Høiland-Jørgensen
@ 2021-03-31 12:59 ` Ong, Boon Leong
1 sibling, 0 replies; 5+ messages in thread
From: Ong, Boon Leong @ 2021-03-31 12:59 UTC (permalink / raw)
To: Jesper Dangaard Brouer
Cc: Alexei Starovoitov, Daniel Borkmann, David S . Miller,
Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend,
Toshiaki Makita, netdev, bpf, linux-kernel
>> diff --git a/net/core/xdp.c b/net/core/xdp.c
>> index 05354976c1fc..4eaa28972af2 100644
>> --- a/net/core/xdp.c
>> +++ b/net/core/xdp.c
>> @@ -350,7 +350,8 @@ static void __xdp_return(void *data, struct
>xdp_mem_info *mem, bool napi_direct,
>> /* mem->id is valid, checked in
>xdp_rxq_info_reg_mem_model() */
>> xa = rhashtable_lookup(mem_id_ht, &mem->id,
>mem_id_rht_params);
>> page = virt_to_head_page(data);
>> - napi_direct &= !xdp_return_frame_no_direct();
>> + if (napi_direct)
>> + napi_direct &= !xdp_return_frame_no_direct();
>
>if (napi_direct && xdp_return_frame_no_direct())
> napi_direct = false;
>
>I wonder if this code would be easier to understand?
>
Ya, I think this is more readable. Thanks.
I will send v2.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2021-03-29 8:00 [PATCH net 1/1] xdp: fix xdp_return_frame() kernel BUG throw for page_pool memory model Ong Boon Leong
2021-03-29 15:02 ` Jesper Dangaard Brouer
2021-03-29 16:25 ` Toke Høiland-Jørgensen
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