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Message-ID: <d8973f3c-f4ff-89dc-7e68-b327571eff69@yandex-team.ru> Date: Thu, 6 Apr 2023 18:06:49 +0300 From: Denis Plotnikov <den-plotnikov@...dex-team.ru> To: Simon Horman <simon.horman@...igine.com> Cc: Bjorn Helgaas <helgaas@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, shshaikh@...vell.com, manishc@...vell.com, GR-Linux-NIC-Dev@...vell.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org Subject: Re: [PATCH] qlcnic: check pci_reset_function result On 06.04.2023 14:43, Simon Horman wrote: > On Thu, Apr 06, 2023 at 12:23:49PM +0300, Denis Plotnikov wrote: >> On 06.04.2023 10:03, Simon Horman wrote: >>> On Wed, Apr 05, 2023 at 02:37:08PM -0500, Bjorn Helgaas wrote: >>>> On Wed, Apr 05, 2023 at 03:04:39PM +0200, Simon Horman wrote: >>>>> On Mon, Apr 03, 2023 at 01:58:49PM +0300, Denis Plotnikov wrote: >>>>>> On 31.03.2023 20:52, Simon Horman wrote: >>>>>>> On Fri, Mar 31, 2023 at 11:06:05AM +0300, Denis Plotnikov wrote: >>>>>>>> Static code analyzer complains to unchecked return value. >>>>>>>> It seems that pci_reset_function return something meaningful >>>>>>>> only if "reset_methods" is set. >>>>>>>> Even if reset_methods isn't used check the return value to avoid >>>>>>>> possible bugs leading to undefined behavior in the future. >>>>>>>> >>>>>>>> Signed-off-by: Denis Plotnikov <den-plotnikov@...dex-team.ru> >>>>>>> nit: The tree this patch is targeted at should be designated, probably >>>>>>> net-next, so the '[PATCH net-next]' in the subject. >>>>>>> >>>>>>>> --- >>>>>>>> drivers/net/ethernet/qlogic/qlcnic/qlcnic_ctx.c | 4 +++- >>>>>>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>>>>>> >>>>>>>> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_ctx.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_ctx.c >>>>>>>> index 87f76bac2e463..39ecfc1a1dbd0 100644 >>>>>>>> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_ctx.c >>>>>>>> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_ctx.c >>>>>>>> @@ -628,7 +628,9 @@ int qlcnic_fw_create_ctx(struct qlcnic_adapter *dev) >>>>>>>> int i, err, ring; >>>>>>>> if (dev->flags & QLCNIC_NEED_FLR) { >>>>>>>> - pci_reset_function(dev->pdev); >>>>>>>> + err = pci_reset_function(dev->pdev); >>>>>>>> + if (err && err != -ENOTTY) >>>>>>> Are you sure about the -ENOTTY part? >>>>>>> >>>>>>> It seems odd to me that an FLR would be required but reset is not supported. >>>>>> No, I'm not sure. My logic is: if the reset method isn't set than >>>>>> pci_reset_function() returns -ENOTTY so treat that result as ok. >>>>>> pci_reset_function may return something different than -ENOTTY only if >>>>>> pci_reset_fn_methods[m].reset_fn is set. >>>>> I see your reasoning: -ENOTTY means nothing happened, and probably that is ok. >>>>> I think my main question is if that can ever happen. >>>>> If that is unknown, then I think this conservative approach makes sense. >>>> The commit log mentions "reset_methods", which I don't think is really >>>> relevant here because reset_methods is an internal implementation >>>> detail. The point is that pci_reset_function() returns 0 if it was >>>> successful and a negative value if it failed. >>>> >>>> If the driver thinks the device needs to be reset, ignoring any >>>> negative return value seems like a mistake because the device was not >>>> reset. >>>> >>>> If the reset is required for a firmware update to take effect, maybe a >>>> diagnostic would be helpful if it fails, e.g., the other "Adapter >>>> initialization failed. Please reboot" messages. >>>> >>>> "QLCNIC_NEED_FLR" suggests that the driver expects an FLR (as opposed >>>> to other kinds of reset). If the driver knows that all qlcnic devices >>>> support FLR, it could use pcie_flr() directly. >>>> >>>> pci_reset_function() does have the possibility that the reset works on >>>> some devices but not all. Secondary Bus Reset fails if there are >>>> other functions on the same bus, e.g., a multi-function device. And >>>> there's some value in doing the reset the same way in all cases. >>>> >>>> So I would suggest something like: >>>> >>>> if (dev->flags & QLCNIC_NEED_FLR) { >>>> err = pcie_flr(dev->pdev); >>>> if (err) { >>>> dev_err(&pdev->dev, "Adapter reset failed (%d). Please reboot\n", err); >>>> return err; >>>> } >>>> dev->flags &= ~QLCNIC_NEED_FLR; >>>> } >>>> >>>> Or, if there are qlcnic devices that don't support FLR: >>>> >>>> if (dev->flags & QLCNIC_NEED_FLR) { >>>> err = pci_reset_function(dev->pdev); >>>> if (err) { >>>> dev_err(&pdev->dev, "Adapter reset failed (%d). Please reboot\n", err); >>>> return err; >>>> } >>>> dev->flags &= ~QLCNIC_NEED_FLR; >>>> } >>> Thanks Bjorn, >>> >>> that is very helpful. >>> >>> I think that in order to move to option #1 some information would be needed >>> from those familiar with the device(s). As it is a more invasive change - >>> pci_reset_function -> pcie_flr. >>> >>> So my feeling is that, in lieu of such feedback, option #2 is a good >>> improvement on the current code. >>> >>> OTOH, this driver is 'Supported' as opposed to 'Maintained'. >>> So perhaps we can just use our best judgement and go for option #1. >> So, it looks like option #2 is the safest choice as we do reset only if FLR >> is needed (when pci_reset_function() makes sense) >> >> If all agree with that I'll re-send the path > Yes. Maybe wait 24h, and if there is no further feedback go ahead with that > plan? Ok, will do so. Thanks!
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