linux-kernel - RE: [PATCH v2 1/1] drivers:hv:vmbus drivers:hv:vmbus Allow for more than one MMIO range for children

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Date:	Fri, 6 Feb 2015 16:57:05 +0000
From:	Jake Oshins <jakeo@...rosoft.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	KY Srinivasan <kys@...rosoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>
Subject: RE: [PATCH v2 1/1] drivers:hv:vmbus drivers:hv:vmbus Allow for more
 than one MMIO range for children

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Friday, February 6, 2015 7:04 AM
> To: Jake Oshins
> Cc: gregkh@...uxfoundation.org; KY Srinivasan; linux-kernel@...r.kernel.org;
> devel@...uxdriverproject.org; olaf@...fle.de; apw@...onical.com
> Subject: Re: [PATCH v2 1/1] drivers:hv:vmbus drivers:hv:vmbus Allow for more
> than one MMIO range for children
> 
> Jake Oshins <jakeo@...rosoft.com> writes:
> 
> > This set of changes finds the _CRS object in the ACPI namespace
> > that contains memory address space descriptors, intended to convey
> > to VMBus which ranges of memory-mapped I/O space are available for
> > child devices, and then builds a resource list that contains all
> > those ranges.  Without this change, only some of the memory-mapped
> > I/O space will be available for child devices, and only in some
> > virtual BIOS configurations (Generation 2 VMs).
> >
> > This patch has been updated with feedback from Vitaly Kuznetsov.
> > Cleanup is now driven by the acpi remove callback function.
> 
> Sorry for beeing late with this message but I'm seeing issues with this
> commit. I added some debug to figure out what's going on and here is
> what I see:
> 
> With Gen1 VM we end up doing request_resource for two ranges:
> f8000000 - fffbffff
> fe0000000 - fffefffff
> 
> request_resource() fails (as we already have PCI device at f8000000 I
> suppose?) but we don't check the return value. release_resource on
> module unload crashes the kernel:
> [   78.314344] BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000030
> [   78.315021] IP: [<ffffffff8107fac5>] release_resource+0x25/0x90
> [   78.315021] PGD 78c67067 PUD 78c5a067 PMD 0
> [   78.315021] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
> [   78.315021] Modules linked in: hv_vmbus(-)
> ...
> If I'm not mistaken, before the change we didn't do any
> request_resource() for Gen1 VMs at all.
> 
> With Gen2 VM we do request_resource for fe0000000 - fffffffff range
> only, that means this commit doesn't change anything.
> 
> Can you please take a look? I'd like to help but I don't completely
> understand the essense of the change wrt Gen1 VMs with PCI devices.
> 

I'll take a look immediately.

Thanks,
Jake
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