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

Re: [Xen-devel] [PATCH 2/7] ARM: vGICv3: drop GUEST_GICV3_RDIST_REGIONS symbol

Hi Andre,

On 24/01/18 16:58, Andre Przywara wrote:
On 24/01/18 16:13, Julien Grall wrote:
Hi Andre,

On 24/01/18 14:35, Andre Przywara wrote:
Architecturally there is only one GICv3 redistributor region.
Drop the symbol which suggested that was a delibarate choice for Xen
guests, instead hard code the "1" in the appropriate places, along with
a comment to explain the reasons.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
   xen/arch/arm/vgic-v3.c        | 17 ++++++++++++-----
   xen/include/public/arch-arm.h |  1 -
   2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index af16dfd005..7d3ea171b4 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -1640,8 +1640,18 @@ static int vgic_v3_vcpu_init(struct vcpu *v)
     static inline unsigned int vgic_v3_rdist_count(struct domain *d)
-    return is_hardware_domain(d) ? vgic_v3_hw.nr_rdist_regions :
-               GUEST_GICV3_RDIST_REGIONS;
+    /*
+     * Architecturally there is only one GICv3 redistributor region.
+     * The GICv3 DT binding provisions for multiple regions, since
there are
+     * platforms out there which break this architectural assumption.
+     * ACPI does not support this workaround at all.

This is not true. The ACPI spec supports multiple regions of
redistributors. What ACPI does not support is a different stride.

Ah, that's true. Sorry for that, I was a bit too enthusiastic here ;-)
Will change the comment, definitely.
However I would still be interested in dropping the
GUEST_GICV3_RDIST_REGIONS symbol, possibly replacing it with
DEFAULT_GICV3_RDIST_REGIONS, avoiding the misleading GUEST_ prefix.

Why GUEST_ is misleading?

Bear in mind that the toolstack is in charge of the memory map. Not the hypervisor.

Today, the memory map is static and so rather than implementing a bunch of hypercalls the hypervisor is directly using the value.


Julien Grall

Xen-devel mailing list



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