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Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control o
From: |
Jan Beulich |
Subject: |
Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register |
Date: |
Mon, 13 Apr 2015 13:40:59 +0100 |
>>> On 13.04.15 at 13:47, <address@hidden> wrote:
> On Mon, Apr 13, 2015 at 12:34:34PM +0100, Jan Beulich wrote:
>> >>> On 13.04.15 at 13:19, <address@hidden> wrote:
>> > Yes Linux can't fix firmware 1st mode, but
>> > PCI express spec says what firmware should do in this case:
>> >
>> > IMPLEMENTATION NOTE Software UR Reporting Compatibility with 1.0a Devices
>> >
>> > With 1.0a device Functions, 96 if the Unsupported Request
>> > Reporting
>
>> > Enable bit is set, the Function
>> > when operating as a Completer will send an uncorrectable error
>> > Message (if enabled) when a UR
>> > error is detected. On platforms where an uncorrectable error
> Message
>> > is handled as a System Error,
>> > this will break PC-compatible Configuration Space probing, so
>> > software/firmware on such
>> > platforms may need to avoid setting the Unsupported Request
>> > Reporting Enable bit.
>> > With device Functions implementing Role-Based Error Reporting,
>> > setting the Unsupported Request
>> > Reporting Enable bit will not interfere with PC-compatible
>> > Configuration Space probing, assuming
>> > that the severity for UR is left at its default of non-fatal.
>> > However, setting the Unsupported Request
>> > Reporting Enable bit will enable the Function to report UR errors
>> > detected with posted Requests,
>> > helping avoid this case for potential silent data corruption.
>> > On platforms where robust error handling and PC-compatible
>> > Configuration Space probing is
>> > required, it is suggested that software or firmware have the
>> > Unsupported Request Reporting Enable
>> > bit Set for Role-Based Error Reporting Functions, but clear for
>> > 1.0a
>
>> > Functions. Software or
>> > firmware can distinguish the two classes of Functions by examining
>> > the Role-Based Error Reporting
>> > bit in the Device Capabilities register.
>> >
>> >
>> > What I think you have is a very old 1.0a system, and you set Unsupported
>> > Request Reporting Enable.
>> >
>> > Can you confirm?
>>
>> No. In at least one of the two cases we got reports of the original
>> problem, triggering the finding of this issue, this is a brand new one,
>> only soon to become available publicly. Furthermore I'm being
>> confused by the mention of PC-compatible config space probing
>> above: The URs we talk about here don't result from config space
>> accessed at all.
>
> OK. Can you please explain why does UR cause a system error then?
> It looks like a hardware bug: PCIE 1.1 seems to say it shouldn't.
Quite possible. Looking at the ITP log we were provided, the UR
severity bit is clear (non-fatal), yet the error got surfaced to the
OS as a fatal one (I would guess because it validly gets flagged as
uncorrectable at the same time).
Jan
- Re: [Qemu-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/01
- Re: [Qemu-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Stefano Stabellini, 2015/04/01
- Re: [Qemu-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/01
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Andrew Cooper, 2015/04/01
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/01
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Jan Beulich, 2015/04/13
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/13
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Jan Beulich, 2015/04/13
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/13
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register,
Jan Beulich <=
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/13
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Jan Beulich, 2015/04/13
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/20
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Jan Beulich, 2015/04/20
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Michael S. Tsirkin, 2015/04/20
- Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Jan Beulich, 2015/04/20
Re: [Qemu-devel] [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register, Ian Campbell, 2015/04/01