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

To: Simon Kagstrom <simon.kagstrom@xxxxxx>
Subject: Re: [Xen-devel] [PATCH] paging_enabled and non-HVM guests
From: Hollis Blanchard <hollisb@xxxxxxxxxx>
Date: Tue, 09 May 2006 14:53:46 -0500
Cc: xen-devel list <xen-devel@xxxxxxxxxxxxxxxxxxx>
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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.

Hollis Blanchard
IBM Linux Technology Center

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