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Re: [Xen-devel] [V8 PATCH 7/8] pvh dom0: add check for pvh in vioapic_range



On 04/07/2014 07:59 AM, Jan Beulich wrote:
On 05.04.14 at 03:00, <mukesh.rathor@xxxxxxxxxx> wrote:
On Tue, 01 Apr 2014 16:09:15 +0100
"Jan Beulich" <JBeulich@xxxxxxxx> wrote:

On 01.04.14 at 16:40, <george.dunlap@xxxxxxxxxxxxx> wrote:
On 03/24/2014 09:34 AM, Jan Beulich wrote:
On 22.03.14 at 02:39, <mukesh.rathor@xxxxxxxxxx> wrote:
--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -238,8 +238,13 @@ static int vioapic_write(

   static int vioapic_range(struct vcpu *v, unsigned long addr)
   {
-    struct hvm_hw_vioapic *vioapic = domain_vioapic(v->domain);
+    struct hvm_hw_vioapic *vioapic;
+
+    /* pvh uses event channel callback */
+    if ( is_pvh_vcpu(v) )
+        return 0;

+    vioapic = domain_vioapic(v->domain);
I can see why the extra check is needed, but I can't see why you
convert the initializer to an assignment: Afaict domain_vioapic()
is safe even if d->arch.hvm_domain.vioapic == NULL.
Or better yet, just make it something like:

return vioapic && ((addr >= [...original range check]))

That way we don't have to have a PVH-specific hook at all.  If a
domain doesn't have a vioapic for any reason, return 0.
No, vioapic isn't going to be NULL for PVH:

#define domain_vioapic(d)
(&(d)->arch.hvm_domain.vioapic->hvm_hw_vioapic)
No, viopaic is NULL for PVH, hence the patch. So, can prob just check
for the ptr like George suggests and remove the pvh check.
Sorry, no - I agree that d->arch.hvm_domain.vioapic is NULL for
PVH, but that doesn't mean the result of domain_vioapic(d) is too
(see the quoted #define above).

I interpreted Mukesh saying "check for the ptr" as, "check d->arch_hvm.domain.vioapic", not "check domain_vioapic(d)".

 -George

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