[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Workings/effectiveness of the xen-acpi-processor driver



On 05/02/2012 05:41 PM, Konrad Rzeszutek Wilk wrote:
On Wed, May 02, 2012 at 02:31:07PM -0700, Boris Ostrovsky wrote:
On 05/02/2012 01:14 PM, Konrad Rzeszutek Wilk wrote:
On Wed, May 02, 2012 at 01:06:34PM -0400, Boris Ostrovsky wrote:
On 05/02/2012 12:08 PM, Konrad Rzeszutek Wilk wrote:
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index a8f8844..d816448 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -811,7 +811,29 @@ static void xen_io_delay(void)
  #ifdef CONFIG_X86_LOCAL_APIC
  static u32 xen_apic_read(u32 reg)
  {
-       return 0;
+       struct xen_platform_op op = {
+               .cmd = XENPF_get_cpuinfo,
+               .interface_version = XENPF_INTERFACE_VERSION,
+               .u.pcpu_info.xen_cpuid = 0,


Is this always zero? This will probably solve the current problem

Its a CPU number (not tied in to APIC or ACPI IDs).

Why not use CPU number instead of zero here?

The issue was only with the bootup CPU - so was using the Xen's
bootup CPU number - which is zero (as is Linux's).

I agree that for this particular problem this may be sufficient.

My concern is that in the future someone may decide to use apic_read(APIC_ID) or read_apic_id() for some other purpose and they won't get expected result (i.e. on all CPUs they will get the same answer).




but I am wondering whether in the future we might hit another bug
because this routine will return the same APICID for all VCPUs.

  Later on it does a check for 'smp_processor_id()' - and if
that is anything but zero it will bail out.

Can you point me to the check you are referring to?

if (!xen_initial_domain() || smp_processor_id())

I don't see this line --- neither in the mainline nor in your kernel. Which kernel and which routine is this in?

BTW, this patch doesn't quite work, xen-acpi-processor driver fails to load with the same error as before. I'll look at this tomorrow more carefully.


-boris




-boris



So this shoudl solve the problem for the bootup processor.

-boris


+       };
+       int ret = 0;
+
+       /* Shouldn't need this as APIC is turned off for PV, and we only
+        * get called on the bootup processor. But just in case. */
+       if (!xen_initial_domain() || smp_processor_id())
+               return 0;
+
+       if (reg == APIC_LVR)
+               return 0x10;
+
+       if (reg != APIC_ID)
+               return 0;
+
+       ret = HYPERVISOR_dom0_op(&op);
+       if (ret)
+               return 0;
+
+       return op.u.pcpu_info.apic_id;
  }

  static void xen_apic_write(u32 reg, u32 val)






_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.