[Xen-devel] Re: Ping: regressions from post-3.2.3 c/s 17041

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 02.07.10 at 13:24, Christoph Egger <Christoph.Egger@xxxxxxx> wrote:
> The testing results shown so far mean that c/s 16898 has a dependency
> to at least one c/s in xen-unstable prior to 17575 that has *not* been
> backported to Xen-3.2-testing.
> 
> The issue is described in c/s 17202 (xen-unstable tree):
> -----------------------------------------------------------------
> description:    SVM: handle page faults in emulated instruction fetches
> 
> Deal with failures in hvm_copy_from_guest_virt when fetching
> instructions in the various SVM emulation paths. Since we know that
> the instruction was fetchable by the hardware, we can usually just
> return from the VMEXIT and try again; whatever caused us to fail will
> cause the hardware to fail next time and we'll get the correct exit
> code.
> -----------------------------------------------------------------
> 
> Unfortunately, the SVM emulation code has been rewritten in
> c/s 17090 (xen-unstable tree) and not been backported to Xen 3.2.x.
> Therefore, the real fix is way more complicated than the diff
> from c/s 17202.

Two main things this doesn't answer:

1) The changes we talk about here don't (afaics) touch the
handle_mmio() path at all, yet your testing says that this path
is affected.

2) According to the second of the messages

> (XEN) instrlen.c:252:d6 Cannot read from address 802eb001 (eip 802eb001, mode 
> 2)

the guest is in 16-bit mode. Since 64-bit kernels don't call 16-bit
BIOS routines, this must be before the kernel even starts. If
however this is BIOS code, the reported instruction pointer looks
rather bogus, and there should presumably not be any talk about
page faults.

Jan


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