Re: [Xen-users] xen 4.4 errors and misunderstanding

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-05-11 at 12:41 +0300, darkshvein l wrote:
> >What about them? 
> Videocard work in windows with 3 gb ram
> and not work with 4 gb or more. 

Oh, that sort of memory barrier. I thought you meant
http://en.wikipedia.org/wiki/Memory_barrier.

I'm afraid I've no idea about the issue you refer to (which I would call
a "memory limit" FWIW).

Ian.


> 
> 11 ÐÐÐ 2015 Ð. 12:56 ÐÐÐÑÐÐÐÐÑÐÐÑ "Ian Campbell"
> <ian.campbell@xxxxxxxxxx> ÐÐÐÐÑÐÐ:
>         On Sun, 2015-05-10 at 11:43 +0300, darkshvein l wrote:
>         > Good day, people.
>         >
>         > I run windows on xen 4.4.
>         >
>         > After decreasing RAM from 9 to 3 Gb it was works.
>         >
>         > But, I met another problem
>         >
>         >
>         >
>         > >libxl: error: libxl_pci.c:990:libxl__device_pci_reset: The
>         kernel
>         > doesn't support reset from sysfs for PCI device 0000:01:00.0
>         >
>         >
>         > 0000:01:00.0 - radeon 7850, xen 4.1 all fine.
>         >
>         > 1.where/what is this kernel reset option?
>         
>         Resetting a PCI device should be simple, after all there are
>         more or
>         less standardized ways of doing so. However in reality many
>         devices do
>         not implement these interfaces or implement customise or
>         quirky ones.
>         
>         So Xen relies on the kernel (which has drivers for the PCI bus
>         and often
>         the specific hardware device) to know all this and to present
>         a reset
>         method to userspace (via sysfs). However the kernel cannot
>         always do
>         this (i..e if it lacks a quirk for a given device).
>         
>         If a device cannot be reset prior to passthrough then it may
>         not be
>         completely quiesced, which can cause strange behaviour.
>         
>         In practice it seems to often be the case that it is ok to
>         passthrough
>         without resetting, especially if you have configured pciback
>         such that
>         the device is never actively used by dom0 before you pass it
>         to the
>         guest.
>         
>         > 2. what about memory barrier?
>         
>         What about them?
>         
>         Ian.
>         
>         



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