On 12/31/18 12:27 AM, Tariq Toukan wrote: > > > On 1/27/2018 2:41 PM, jianchao.wang wrote: >> Hi Tariq >> >> Thanks for your kindly response. >> That's really appreciated. >> >> On 01/25/2018 05:54 PM, Tariq Toukan wrote: >>> >>> >>> On 25/01/2018 8:25 AM, jianchao.wang wrote: >>>> Hi Eric >>>> >>>> Thanks for you kindly response and suggestion. >>>> That's really appreciated. >>>> >>>> Jianchao >>>> >>>> On 01/25/2018 11:55 AM, Eric Dumazet wrote: >>>>> On Thu, 2018-01-25 at 11:27 +0800, jianchao.wang wrote: >>>>>> Hi Tariq >>>>>> >>>>>> On 01/22/2018 10:12 AM, jianchao.wang wrote: >>>>>>>>> On 19/01/2018 5:49 PM, Eric Dumazet wrote: >>>>>>>>>> On Fri, 2018-01-19 at 23:16 +0800, jianchao.wang wrote: >>>>>>>>>>> Hi Tariq >>>>>>>>>>> >>>>>>>>>>> Very sad that the crash was reproduced again after applied the patch. >>>>>>>> >>>>>>>> Memory barriers vary for different Archs, can you please share more details regarding arch and repro steps? >>>>>>> The hardware is HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 12/27/2015 >>>>>>> The xen is installed. The crash occurred in DOM0. >>>>>>> Regarding to the repro steps, it is a customer's test which does heavy disk I/O over NFS storage without any guest. >>>>>>> >>>>>> >>>>>> What is the finial suggestion on this ? >>>>>> If use wmb there, is the performance pulled down ? >>> >>> I want to evaluate this effect. >>> I agree with Eric, expected impact is restricted, especially after batching the allocations.> >>>>> >>>>> Since https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pub_scm_linux_kernel_git_davem_net-2Dnext.git_commit_-3Fid-3Ddad42c3038a59d27fced28ee4ec1d4a891b28155&d=DwICaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=7WdAxUBeiTUTCy8v-7zXyr4qk7sx26ATvfo6QSTvZyQ&m=c0oI8duFkyFBILMQYDsqRApHQrOlLY_2uGiz_utcd7s&s=E4_XKmSI0B63qB0DLQ1EX_fj1bOP78ZdeYADBf33B-k&e= >>>>> >>>>> we batch allocations, so mlx4_en_refill_rx_buffers() is not called that often. >>>>> >>>>> I doubt the additional wmb() will have serious impact there. >>>>> >>> >>> I will test the effect (it'll be beginning of next week). >>> I'll update so we can make a more confident decision. >>> >> I have also sent patches with wmb and batching allocations to customer and let them check whether the performance is impacted. >> And update here asap when get feedback. >> >>> Thanks, >>> Tariq >>> > > Hi Jianchao, > > I am interested to push this bug fix. > Do you want me to submit, or do it yourself? > Can you elaborate regarding the arch with the repro? > > This is the patch I suggest: > > --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c > +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c > @@ -161,6 +161,8 @@ static bool mlx4_en_is_ring_empty(const struct > mlx4_en_rx_ring *ring) > > static inline void mlx4_en_update_rx_prod_db(struct mlx4_en_rx_ring *ring) > { > + /* ensure rx_desc updating reaches HW before prod db updating */ > + wmb(); > *ring->wqres.db.db = cpu_to_be32(ring->prod & 0xffff); > } > Hi Tariq Happy new year ! The customer provided confused test result for us. The fix cannot fix their issue. And we finally find a upstream fix 5d70bd5c98d0e655bde2aae2b5251bdd44df5e71 (net/mlx4_en: fix potential use-after-free with dma_unmap_page) and killed the issue during Oct 2018. That's really a long way. Please go ahead with this patch. Thanks Jianchao
