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Re: [Xen-devel] 4.2.0-rc4 bug: memory events for CR3 register are broken (working in 4.1.3)


  • To: Navin Patel <navinjpatel336@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxx>
  • From: Keir Fraser <keir.xen@xxxxxxxxx>
  • Date: Sun, 16 Sep 2012 17:35:02 +0100
  • Cc: Steven Maresca <steve@xxxxxxxxxxxx>
  • Delivery-date: Sun, 16 Sep 2012 16:35:39 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac2UKTgiuzIeLUHbCECcraVtXYR+wg==
  • Thread-topic: [Xen-devel] 4.2.0-rc4 bug: memory events for CR3 register are broken (working in 4.1.3)

This issue is known and a fix has been proposed. It’s too late for 4.2.0 unfortunately, but will be fixed for 4.2.1.

 -- Keir

On 16/09/2012 16:52, "Navin Patel" <navinjpatel336@xxxxxxxxx> wrote:

Greetings,

I have tested some of my research code watching for CR3 memory events on Xen 4.2.0-rc4, and I have discovered that CR3 events are not being delivered.  This did work properly in 4.1.3, so I think 4.2.0-rc4 may has a bug.

 This feature has been removed maybe?

Crude test  to confirm this can be had by changing tools/tests/xen-access/xen-access.c : replace HVM_PARAM_MEMORY_EVENT_INT3 with HVM_PARAM_MEMORY_EVENT_CR3 and rebuild (line 569 and 571 in 4.2.0-rc4).

Then (while domU is scheduling programs/launching new processes) run like int3 were still the constant value: ./xen-access $DOMID int3

4.1.3: In the switch/case, printf will show "UNKNOWN REASON CODE $C", with c == 3 == MEM_EVENT_REASON_CR3 (no case built to detect CR3 evnets).

4.2.0-rc4: In the switch/case, printf will never show "UNKNOWN REASON CODE 3"

Cheers,
Navin


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