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Message-ID: <32f18da1-eeb9-3cd6-398d-77f76596b7c3@yandex-team.ru> Date: Thu, 6 Apr 2023 12:23:49 +0300 From: Denis Plotnikov <den-plotnikov@...dex-team.ru> To: Simon Horman <simon.horman@...igine.com>, Bjorn Helgaas <helgaas@...nel.org> Cc: 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 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
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