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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 12:34:34 +0100 |
>>> 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.
> You will have other problems if your firmware doesn't follow the spec. So
> how about either
>
> - Don't use firmware 1st mode with pci express
> (Seems no reason to do firmware 1st for PCIE, architecture is completely
> standard. I saw mentions of using combined/parallel mode, using AER for
> some
> devices but not others, but I don't know how this is supposed to be
> enabled.
> Any idea?)
>
> or
>
> - ask your vendor to update firmware if it doesn't do the right thing
Both not very practical suggestions, based on experience.
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 <=
- 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, 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