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Re: [Xen-devel] [PATCH V3 04/10] arm/gic-v3: Parse per-cpu redistributor entry in GICC subtable



Hi Shanker,

On 28/06/16 15:33, Shanker Donthineni wrote:


On 06/28/2016 08:51 AM, Shanker Donthineni wrote:
Hi Julien,


On 06/28/2016 05:40 AM, Julien Grall wrote:
Hello Shanker,

On 27/06/16 21:33, Shanker Donthineni wrote:
@@ -1397,6 +1408,36 @@ gic_acpi_parse_madt_distributor(struct
acpi_subtable_header *header,
  }

  static int __init
+gic_acpi_parse_cpu_redistributor(struct acpi_subtable_header *header,
+                                 const unsigned long end)
+{
+    struct acpi_madt_generic_interrupt *processor;
+    u32 size;
+
+    processor = (struct acpi_madt_generic_interrupt *)header;
+    if ( !(processor->flags & ACPI_MADT_ENABLED) )
+        return 0;

You did not answer to my question on previous version of this patch.
You said that "Disabled GICC entries should be skipped because its
Redistributor region is not always-on power domain." However from my
understanding, an usable CPU may have his Redistributor in the not
always-on power domain. So the issue would the same, correct?


The gicv3_populate_rdist() is not supposed to read GICR registers if
the  the associated hardware GICR block is in power-off state. The CPU
accesses to disabled GICR region leads to either a system hang or an
unexpected behavior.


The description of flag ACPI_MADT_ENABLED in ACPI-6.1 says "If zero,
this processor in unusable, and the operating system support will not
attempt to use it".

Ok.  The patch looks good to me then.

Regards,

--
Julien Grall

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