Re: [Xen-devel] [PATCH V3 2/2] Xen/PCIback: Implement PCI flr/slot/bus reset with 'reset' SysFS attribute

[Håkon Alstadheim <hakon@xxxxxxxxxxxxxxxxxx>]

Den 19.10.2020 17:16, skrev Håkon Alstadheim:
> Den 19.10.2020 13:00, skrev George Dunlap:
> > > On Jan 31, 2020, at 3:33 PM, Wei Liu <wl@xxxxxxx> wrote:
> > >
> > > On Fri, Jan 17, 2020 at 02:13:04PM -0500, Rich Persaud wrote:
> > > > On Aug 26, 2019, at 17:08, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> > > > > Hi,
> > > > >
> > > > > > On Mon, Oct 08, 2018 at 10:32:45AM -0400, Boris Ostrovsky wrote:
> > > > > > > On 10/3/18 11:51 AM, Pasi Kärkkäinen wrote:
> > > > > > > On Wed, Sep 19, 2018 at 11:05:26AM +0200, Roger Pau Monné wrote:
> > > > > > > > On Tue, Sep 18, 2018 at 02:09:53PM -0400, Boris Ostrovsky wrote:
> > > > > > > > > On 9/18/18 5:32 AM, George Dunlap wrote:
> > > > > > > > > > > On Sep 18, 2018, at 8:15 AM, Pasi Kärkkäinen <pasik@xxxxxx> 
> > > > > > > > > > > wrote:
> > > > > > > > > > > Hi,
> > > > > > > > > > > On Mon, Sep 17, 2018 at 02:06:02PM -0400, Boris Ostrovsky 
> > > > > > > > > > > wrote:
> > > > > > > > > > > > What about the toolstack changes? Have they been accepted? 
> > > > > > > > > > > > I vaguely
> > > > > > > > > > > > recall there was a discussion about those changes but don't 
> > > > > > > > > > > > remember how
> > > > > > > > > > > > it ended.
> > > > > > > > > > > I don't think toolstack/libxl patch has been applied yet 
> > > > > > > > > > > either.
> > > > > > > > > > > "[PATCH V1 0/1] Xen/Tools: PCI reset using 'reset' SysFS 
> > > > > > > > > > > attribute":
> > > > > > > > > > > https://lists.xen.org/archives/html/xen-devel/2017-12/msg00664.html 
> > > > > > > > > > >
> > > > > > > > > > > "[PATCH V1 1/1] Xen/libxl: Perform PCI reset using 'reset' 
> > > > > > > > > > > SysFS attribute":
> > > > > > > > > > > https://lists.xen.org/archives/html/xen-devel/2017-12/msg00663.html 
> > > > > > > > > Will this patch work for *BSD? Roger?
> > > > > > > > At least FreeBSD don't support pci-passthrough, so none of this 
> > > > > > > > works
> > > > > > > > ATM. There's no sysfs on BSD, so much of what's in libxl_pci.c 
> > > > > > > > will
> > > > > > > > have to be moved to libxl_linux.c when BSD support is added.
> > > > > > > Ok. That sounds like it's OK for the initial pci 'reset' 
> > > > > > > implementation in xl/libxl to be linux-only..
> > > > > > Are these two patches still needed? ISTR they were written 
> > > > > > originally
> > > > > > to deal with guest trying to use device that was previously 
> > > > > > assigned to
> > > > > > another guest. But pcistub_put_pci_dev() calls
> > > > > > __pci_reset_function_locked() which first tries FLR, and it looks 
> > > > > > like
> > > > > > it was added relatively recently.
> > > > > Replying to an old thread.. I only now realized I forgot to reply 
> > > > > to this message earlier.
> > > > > afaik these patches are still needed. Håkon (CC'd) wrote to me in 
> > > > > private that
> > > > > he gets a (dom0) Linux kernel crash if he doesn't have these 
> > > > > patches applied.
> > > > >
> > > > > Here are the links to both the linux kernel and libxl patches:
> > > > >
> > > > >
> > > > > "[Xen-devel] [PATCH V3 0/2] Xen/PCIback: PCI reset using 'reset' 
> > > > > SysFS attribute":
> > > > > https://lists.xen.org/archives/html/xen-devel/2017-12/msg00659.html
> > > > >
> > > > > [Note that PATCH V3 1/2 "Drivers/PCI: Export pcie_has_flr() 
> > > > > interface" is already applied in upstream linux kernel, so it's 
> > > > > not needed anymore]
> > > > > "[Xen-devel] [PATCH V3 2/2] Xen/PCIback: Implement PCI 
> > > > > flr/slot/bus reset with 'reset' SysFS attribute":
> > > > > https://lists.xen.org/archives/html/xen-devel/2017-12/msg00661.html
> > > > >
> > > > >
> > > > > "[Xen-devel] [PATCH V1 0/1] Xen/Tools: PCI reset using 'reset' 
> > > > > SysFS attribute":
> > > > > https://lists.xen.org/archives/html/xen-devel/2017-12/msg00664.html
> > > > >
> > > > > "[Xen-devel] [PATCH V1 1/1] Xen/libxl: Perform PCI reset using 
> > > > > 'reset' SysFS attribute":
> > > > > https://lists.xen.org/archives/html/xen-devel/2017-12/msg00663.html
> > > > [dropping Linux mailing lists]
> > > >
> > > > What is required to get the Xen patches merged?  Rebasing against Xen
> > > > master?  OpenXT has been carrying a similar patch for many years and
> > > > we would like to move to an upstream implementation.  Xen users of PCI
> > > > passthrough would benefit from more reliable device reset.
> > > Rebase and resend?
> > >
> > > Skimming that thread I think the major concern was backward
> > > compatibility. That seemed to have been addressed.
> > >
> > > Unfortunately I don't have the time to dig into Linux to see if the
> > > claim there is true or not.
> > >
> > > It would be helpful to write a concise paragraph to say why backward
> > > compatibility is not required.
> > Just going through my old “make sure something happens with this” 
> > mails.  Did anything ever happen with this?  Who has the ball here / 
> > who is this stuck on?
> We're waiting for "somebody" to testify that fixing this will not 
> adversely affect anyone. I'm not qualified, but my strong belief is 
> that since "reset" or "do_flr"  in the linux kernel is not currently 
> implemented/used in any official distribution, it should be OK.
> Patches still work in current staging-4.14 btw.
Just for the record, attached are the patches I am running on top of 
linux gentoo-sources-5.9.1  and xen-staging-4.14 respectively. (I am 
also running with the patch to mark populated reserved memory that 
contains ACPI tables as "ACPI NVS", not attached here ).

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