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Re: [Xen-devel] [RFC] x86: more debugging adjustments

  • To: Jan Beulich <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Thu, 22 Nov 2007 14:50:57 +0000
  • Delivery-date: Thu, 22 Nov 2007 06:51:55 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcgtFxbLVUdSOpkKEdybPwAX8io7RQ==
  • Thread-topic: [Xen-devel] [RFC] x86: more debugging adjustments

Inject-sstep: Looks fine in principle. A few specific questions:
 * Why is all the RFLAGS.RF logic removed from platform.c?
 * Why is DR6 adjustment done in svm_hvm_inject_exception() rather than
svm_inject_exception() (to match vmx_inject_exception())?
 * Why do some instruction emulations pass NULL to update_guest_eip() and
hence bypass #DB injection? That seems bogus.

Io-brkp: This one needs more explanation about exactly what things are being
improved. There's more going on here than your brief explanation below. My
only comment at this point is that I don't see that supporting CR4.DE==0 is
very useful. I don't subscribe to the view that we should support every
little detail of x86 architecture just because it's there, especially for PV

All other patches are applied and I queued up a couple for 3.1.3 also.

 -- Keir

On 22/11/07 12:50, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> Apart from the cleanup patches just sent I also have two bigger ones in
> the queue. I'm not certain they qualify for 3.2 at this point, though: While
> most of them can be considered enhancements, the io-brkp one (which
> depends on the inject-sstep one) also fixes the issue of guests on x86-64
> not being able to utilize 8-byte breakpoints, and it reduces the likelihood
> of needing to restore the debug registers by only looking at the enable
> bits in the respective conditions (as HVM was already doing).
> Therefore I'd like to understand whether these patches can go in in their
> current shape, or whether I should split out at least the 8-byte bug fix
> and submit this separately.
> Thanks, Jan
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