From: Jan Beulich <firstname.lastname@example.org> To: Boris Ostrovsky <email@example.com> Cc: Juergen Gross <firstname.lastname@example.org>, Konrad Wilk <email@example.com>, "firstname.lastname@example.org" <email@example.com> Subject: Re: [PATCH 1/3] xen-pciback: redo VF placement in the virtual topology Date: Fri, 9 Apr 2021 10:16:31 +0200 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> On 09.04.2021 00:28, Boris Ostrovsky wrote: > > On 4/7/21 10:37 AM, Jan Beulich wrote: >> The commit referenced below was incomplete: It merely affected what >> would get written to the vdev-<N> xenstore node. The guest would still >> find the function at the original function number as long as >> __xen_pcibk_get_pci_dev() wouldn't be in sync. The same goes for AER wrt >> __xen_pcibk_get_pcifront_dev(). >> >> Undo overriding the function to zero and instead make sure that VFs at >> function zero remain alone in their slot. This has the added benefit of >> improving overall capacity, considering that there's only a total of 32 >> slots available right now (PCI segment and bus can both only ever be >> zero at present). >> >> Fixes: 8a5248fe10b1 ("xen PV passthru: assign SR-IOV virtual functions to separate virtual slots") >> Signed-off-by: Jan Beulich <firstname.lastname@example.org> >> Cc: email@example.com >> --- >> Like the original change this has the effect of changing where devices >> would appear in the guest, when there are multiple of them. I don't see >> an immediate problem with this, but if there is we may need to reduce >> the effect of the change. >> Taking into account, besides the described breakage, how xen-pcifront's >> pcifront_scan_bus() works, I also wonder what problem it was in the >> first place that needed fixing. It may therefore also be worth to >> consider simply reverting the original change. > > > Perhaps this is no longer a problem, it's been 9 years since that patch. Have you tried reverting to 8a5248fe10b101104d92d01438f918e899414fd1~1 and testing that? Well, no, for the simple reason that I don't really understand how that change was meant to make a difference. Hence while simply reverting may be an option, it's not something I would want to suggest myself (simply because I couldn't fully justify doing so). Jan
next prev parent reply other threads:[~2021-04-09 8:16 UTC|newest] Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-07 14:35 [PATCH 0/3] xen-pciback: a fix, a workaround, and some simplification Jan Beulich 2021-04-07 14:37 ` [PATCH 1/3] xen-pciback: redo VF placement in the virtual topology Jan Beulich 2021-04-08 22:28 ` Boris Ostrovsky 2021-04-09 8:16 ` Jan Beulich [this message] 2021-04-07 14:37 ` [PATCH 2/3] xen-pciback: reconfigure also from backend watch handler Jan Beulich 2021-04-09 21:43 ` Boris Ostrovsky 2021-04-12 9:44 ` Jan Beulich 2021-04-12 15:55 ` Boris Ostrovsky 2021-04-07 14:37 ` [PATCH 3/3] xen-pciback: simplify vpci's find hook Jan Beulich 2021-04-09 21:45 ` Boris Ostrovsky 2021-04-12 9:50 ` Jan Beulich 2021-04-12 16:05 ` Boris Ostrovsky 2021-04-13 8:09 ` Jan Beulich 2021-04-13 12:54 ` Boris Ostrovsky 2021-04-23 8:05 ` Juergen Gross
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