linux-kernel - Re: [PATCH] PCI: Do not touch siblings in pci_assign_unassigned_bridge

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Message-ID: <CAE9FiQVQ657vDOhdhBq5VC044qt6TUF7FKP_-qy+35g71e56Yg@mail.gmail.com>
Date:	Wed, 18 Jun 2014 21:41:02 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Andreas Noever <andreas.noever@...il.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI: Do not touch siblings in pci_assign_unassigned_bridge_resources

On Wed, Jun 18, 2014 at 3:40 PM, Andreas Noever
<andreas.noever@...il.com> wrote:
> On Wed, Jun 18, 2014 at 1:39 AM, Yinghai Lu <yinghai@...nel.org> wrote:
> It seems to fix the testcase (no unwanted resources are released). But
> why do you reassign bus and not just skip the top level bridge? If one
> of the allocations below bridge failed then a resource of that device
> will be in fail_res and bridge->subordinate will get released anyways?
> Also by not removing fail_res from the list you trigger the code in
> the next loop for the top level bridge (in particular the res->flags =
> 0 line looks dangerous).

Should not be dangerous, just second try.

>
> Could you explain why this function attempts to assign resources two
> times? In which scenario will a second attempt be successful?

For example, at first mmio is assigned (by firmware), but pref mmio fails,
then before second try,  mmio get cleared, then we could separate
mmio and mmio pref. So need to try again for pref mmio.

Also I missed one MEM_64 for hotplug path.

So we need two patches.

Thanks

Yinghai

View attachment "fix_release_sibling_bridge_res.patch" of type "text/x-patch" (1092 bytes)

View attachment "assign_unassigned_bridge_MEM_64.patch" of type "text/x-patch" (865 bytes)