Re: [Qemu-devel] e1000 memory corruption in guest OS

[Paolo Bonzini]

Il 03/03/2014 02:58, Alexey Kardashevskiy ha scritto:
> On 03/02/2014 08:31 AM, Paolo Bonzini wrote:
> > Il 01/03/2014 13:30, Alexey Kardashevskiy ha scritto:
> > > > > Corrupted DMA buffer is 0x e00000 -- 0x7f15c313f000.
> > > > > The e1000 packet is at  0x12ffac2 -- 0x7f15c313eac2.
> > > > >
> > > > > (0x7f15c313f000 - 0x7f15c313eac2) = 0x53e which is less than 0x5aa and
> > > > > (0x5aa - 0x53e) = 0x6c bytes get corrupted.
> > > > >
> > > > > I see here buffer overrun from e1000 and I suspect that your patch just
> > > > > hides this problem. What did I miss?
> > >
> > > Ping, anyone?
> >
> > You missed that this is a Xen-specific problem.  Xen maps things a page at
> > a time, so address_space_map/unmap/rw can operate only on a small part of
> > the requested [address, address+length) range.
>
> Sorry, I am not following you here. Does KVM map things not page-aligned?

Look in exec.c for xen_enabled().  Xen's implementation of 
address_space_map/unmap is completely different.

> > So there is no overrun in e1000.  The patch is incomplete, because it fixes
> > only address_space_rw, but the problem is indeed in exec.c.
>
> So you know what the problem is? We have a bunch of bugreports against
> e1000 breaking things...

This one had been reported and fixed already.

Paolo