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Re: [Xen-devel] [PATCH] paging_enabled and non-HVM guests

To: Hollis Blanchard <hollisb@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] paging_enabled and non-HVM guests
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Tue, 09 May 2006 15:14:42 -0500
Cc: Simon Kagstrom <simon.kagstrom@xxxxxx>, xen-devel list <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ryan Harper <ryanh@xxxxxxxxxx>
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Hollis Blanchard wrote:
On Tue, 2006-05-09 at 13:31 +0200, Simon Kagstrom wrote:
I had a problem with the GDB-server crashing on connections in
xen_ptrace.c:map_domain_va(). paging_enabled() should only be checked
for HVM guests, and the patch adds a check for that.

Signed-off-by: Simon Kagstrom <ska@xxxxxx>

diff -r 4501d60d6add tools/libxc/xc_ptrace.c
--- a/tools/libxc/xc_ptrace.c   Tue May  9 09:57:05 2006
+++ b/tools/libxc/xc_ptrace.c   Tue May  9 13:26:14 2006
@@ -374,7 +374,7 @@
     if (fetch_regs(xc_handle, cpu, NULL))
         return NULL;
- if (!paging_enabled(&ctxt[cpu])) { + if ( (ctxt[cpu].flags & VGCF_HVM_GUEST) && !paging_enabled(&ctxt[cpu])) { static void * v;
         unsigned long page;

I looked at this a couple weeks ago, and I think the real problem is
that the CR registers are never updated in Xen's vcpu structure, and so
xc_vcpu_getcontext() doesn't get them either. So Xen should be fixed; we
shouldn't add workarounds to userland.

I think that the CR registers are never changed during the life of a PV domain. I think all that's needed is for some sane values to be set during domain creation and things start working. I believe Ryan had a patch that did this?


Anthony Liguori

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