From: Amey Narkhede <ameynarkhede03@gmail.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: alex.williamson@redhat.com, info@metux.ne,
raphael.norwitz@nutanix.com, linux-pci@vger.kernel.org,
bhelgaas@google.com, linux-kernel@vger.kernel.org,
alay.shah@nutanix.com, suresh.gumpula@nutanix.com,
shyam.rajendran@nutanix.com, felipe@nutanix.com
Subject: Re: [PATCH 4/4] PCI/sysfs: Allow userspace to query and set device reset mechanism
Date: Sun, 21 Mar 2021 20:27:23 +0530 [thread overview]
Message-ID: <20210321145723.efaj7ywkfhefc4x5@archlinux> (raw)
In-Reply-To: <YFcGlzbaSzQ5Qota@unreal>
On 21/03/21 10:40AM, Leon Romanovsky wrote:
> On Sat, Mar 20, 2021 at 08:59:42AM -0600, Alex Williamson wrote:
> > On Sat, 20 Mar 2021 11:10:08 +0200
> > Leon Romanovsky <leon@kernel.org> wrote:
> > > On Fri, Mar 19, 2021 at 10:23:13AM -0600, Alex Williamson wrote:
> > > >
> > > > What if we taint the kernel or pci_warn() for cases where either all
> > > > the reset methods are disabled, ie. 'echo none > reset_method', or any
> > > > time a device specific method is disabled?
> > >
> > > What does it mean "none"? Does it mean nothing supported? If yes, I think that
> > > pci_warn() will be enough. At least for me, taint is usable during debug stages,
> > > probably if device doesn't crash no one will look to see /proc/sys/kernel/tainted.
> >
> > "none" as implemented in this patch, clearing the enabled function
> > reset methods.
>
> It is far from intuitive, the empty string will be easier to understand,
> because "none" means no reset at all.
>
> >
> > > > I'd almost go so far as to prevent disabling a device specific reset
> > > > altogether, but for example should a device specific reset that fixes
> > > > an aspect of FLR behavior prevent using a bus reset? I'd prefer in that
> > > > case if direct FLR were disabled via a device flag introduced with the
> > > > quirk and the remaining resets can still be selected by preference.
> > >
> > > I don't know enough to discuss the PCI details, but you raised good point.
> > > This sysfs is user visible API that is presented as is from device point
> > > of view. It can be easily run into problems if PCI/core doesn't work with
> > > user's choice.
> > >
> > > >
> > > > Theoretically all the other reset methods work and are available, it's
> > > > only a policy decision which to use, right?
> > >
> > > But this patch was presented as a way to overcome situations where
> > > supported != working and user magically knows which reset type to set.
> >
> > It's not magic, the new sysfs attributes expose which resets are
> > enabled and the order that they're used, the user can simply select the
> > next one. Being able to bypass a broken reset method is a helpful side
> > effect of getting to select a preferred reset method.
>
> Magic in a sense that user has no idea what those resets mean, the
> expectation is that he will blindly iterate till something works.
>
> >
> > > If you want to take this patch to be policy decision tool,
> > > it will need to accept "reset_type1,reset_type2,..." sort of input,
> > > so fallback will work natively.
> >
> > I don't see that as a requirement. We have fall-through support in the
> > kernel, but for a given device we're really only ever going to make use
> > of one of those methods. If a user knows enough about a device to have
> > a preference, I think it can be singular. That also significantly
> > simplifies the interface and supporting code. Thanks,
>
> I'm struggling to get requirements from this thread. You talked about
> policy decision to overtake fallback mechanism, Amey wanted to avoid
> quirks.
Just to clarify I don't want to avoid quirks. I just want device
to be usable even if it doesn't have quirk as the quirk for that
particular device may not be developed at all for different reasons
mentioned earlier.
[...]
Thanks,
Amey
next prev parent reply other threads:[~2021-03-21 14:58 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-12 17:34 [PATCH 0/4] Expose and manage PCI device reset ameynarkhede03
2021-03-12 17:34 ` [PATCH 1/4] PCI: Refactor pcie_flr to follow calling convention of other reset methods ameynarkhede03
2021-03-12 17:34 ` [PATCH 2/4] PCI: Add new bitmap for keeping track of supported reset mechanisms ameynarkhede03
2021-03-14 23:51 ` Pali Rohár
2021-03-12 17:34 ` [PATCH 3/4] PCI: Remove reset_fn field from pci_dev ameynarkhede03
2021-03-14 23:52 ` Pali Rohár
2021-03-12 17:34 ` [PATCH 4/4] PCI/sysfs: Allow userspace to query and set device reset mechanism ameynarkhede03
2021-03-14 23:55 ` Pali Rohár
2021-03-15 13:43 ` Amey Narkhede
2021-03-15 13:52 ` Pali Rohár
2021-03-15 14:34 ` Alex Williamson
2021-03-15 14:52 ` Pali Rohár
2021-03-15 15:03 ` Alex Williamson
2021-03-17 19:02 ` Pali Rohár
2021-03-17 19:15 ` Alex Williamson
2021-03-17 19:24 ` Pali Rohár
2021-03-17 19:32 ` Alex Williamson
2021-03-17 19:40 ` Pali Rohár
2021-03-17 20:00 ` Alex Williamson
2021-03-17 20:13 ` Pali Rohár
2021-03-18 14:31 ` Amey Narkhede
2021-03-23 14:34 ` Pali Rohár
2021-03-23 14:44 ` Alex Williamson
2021-03-23 15:32 ` Amey Narkhede
2021-03-23 16:06 ` Alex Williamson
2021-03-23 16:15 ` Alex Williamson
2021-03-15 15:07 ` Leon Romanovsky
2021-03-15 15:33 ` Amey Narkhede
2021-03-15 16:29 ` Alex Williamson
2021-03-15 18:32 ` Raphael Norwitz
2021-03-17 4:20 ` Leon Romanovsky
2021-03-17 10:24 ` Amey Narkhede
2021-03-17 11:02 ` Leon Romanovsky
2021-03-17 11:23 ` Amey Narkhede
2021-03-17 11:47 ` Leon Romanovsky
2021-03-17 13:17 ` Amey Narkhede
2021-03-17 13:58 ` Leon Romanovsky
2021-03-17 17:31 ` Alex Williamson
2021-03-18 9:09 ` Leon Romanovsky
2021-03-18 14:22 ` Amey Narkhede
2021-03-18 14:57 ` Leon Romanovsky
2021-03-18 17:01 ` Amey Narkhede
2021-03-18 17:35 ` Leon Romanovsky
2021-03-18 17:43 ` Amey Narkhede
2021-03-18 18:14 ` Enrico Weigelt, metux IT consult
2021-03-19 13:05 ` Leon Romanovsky
2021-03-19 15:23 ` Amey Narkhede
2021-03-19 15:37 ` Leon Romanovsky
2021-03-19 15:53 ` Amey Narkhede
2021-03-18 17:58 ` Enrico Weigelt, metux IT consult
2021-03-19 13:07 ` Leon Romanovsky
2021-03-18 16:39 ` Alex Williamson
2021-03-18 17:22 ` Leon Romanovsky
2021-03-18 17:38 ` Amey Narkhede
2021-03-18 18:34 ` Enrico Weigelt, metux IT consult
2021-03-19 12:59 ` Leon Romanovsky
2021-03-19 13:48 ` Enrico Weigelt, metux IT consult
2021-03-19 15:51 ` Leon Romanovsky
2021-03-19 15:57 ` Bjorn Helgaas
2021-03-19 16:24 ` Leon Romanovsky
2021-03-19 16:23 ` Alex Williamson
2021-03-20 9:10 ` Leon Romanovsky
2021-03-20 14:59 ` Alex Williamson
2021-03-21 8:40 ` Leon Romanovsky
2021-03-21 14:57 ` Amey Narkhede [this message]
2021-03-22 17:10 ` Alex Williamson
2021-03-24 10:03 ` Leon Romanovsky
2021-03-24 14:37 ` Alex Williamson
2021-03-24 15:13 ` Leon Romanovsky
2021-03-24 17:17 ` Alex Williamson
2021-03-25 8:37 ` Leon Romanovsky
2021-03-25 14:55 ` Alex Williamson
2021-03-25 16:09 ` Leon Romanovsky
2021-03-25 17:22 ` Amey Narkhede
2021-03-25 17:36 ` Leon Romanovsky
2021-03-25 17:53 ` Alex Williamson
2021-03-26 6:40 ` Leon Romanovsky
2021-03-26 9:18 ` Krzysztof Wilczyński
2021-03-26 12:54 ` Leon Romanovsky
2021-03-26 14:20 ` Alex Williamson
2021-03-27 6:02 ` Leon Romanovsky
2021-03-25 16:26 ` Amey Narkhede
2021-03-25 16:46 ` Leon Romanovsky
2021-03-18 17:51 ` Enrico Weigelt, metux IT consult
[not found] ` <20210312112043.3f2954e3@omen.home.shazbot.org>
2021-03-12 18:40 ` [PATCH 0/4] Expose and manage PCI device reset Amey Narkhede
2021-03-12 18:58 ` Krzysztof Wilczyński
2021-03-12 19:06 ` Amey Narkhede
2021-03-12 19:20 ` Krzysztof Wilczyński
2021-03-13 2:02 ` Raphael Norwitz
2021-03-14 12:09 ` Leon Romanovsky
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