Re: [Xen-devel] [PATCH 0/2] MMIO emulation fixes

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 10 August 2018 13:13
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Subject: RE: [Xen-devel] [PATCH 0/2] MMIO emulation fixes
> 
> >>> On 10.08.18 at 14:08, <Paul.Durrant@xxxxxxxxxx> wrote:
> >>  -----Original Message-----
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: 10 August 2018 13:02
> >> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> >> Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> >> Subject: Re: [Xen-devel] [PATCH 0/2] MMIO emulation fixes
> >>
> >> >>> On 10.08.18 at 12:37, <paul.durrant@xxxxxxxxxx> wrote:
> >> > These are probably both candidates for back-port.
> >> >
> >> > Paul Durrant (2):
> >> >   x86/hvm/ioreq: MMIO range checking completely ignores direction flag
> >> >   x86/hvm/emulate: make sure rep I/O emulation does not cross GFN
> >> >     boundaries
> >> >
> >> >  xen/arch/x86/hvm/emulate.c | 17 ++++++++++++++++-
> >> >  xen/arch/x86/hvm/ioreq.c   | 15 ++++++++++-----
> >> >  2 files changed, 26 insertions(+), 6 deletions(-)
> >>
> >> I take it this isn't yet what we've talked about yesterday on irc?
> >>
> >
> > This is the band-aid fix. I can now show correct handling of a rep mov
> > walking off MMIO into RAM.
> 
> But that's not the problem we're having. In our case the bad behavior
> is with a single MOV. That's why I had assumed that your plan to fiddle
> with null_handler would help in our case as well, while this series clearly
> won't (afaict).
> 

Oh, I see. A single MOV spanning MMIO and RAM has undefined behaviour though as 
I understand it. Am I incorrect?

  Paul

> Jan
> 


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