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Re: [RFC PATCH] arm/gic: Optimize lr_mask type based on GIC version
- To: Jan Beulich <jbeulich@xxxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
- From: "Halder, Ayan Kumar" <ayankuma@xxxxxxx>
- Date: Fri, 6 Mar 2026 10:09:22 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 06 Mar 2026 10:09:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Jan,
On 06/03/2026 08:49, Jan Beulich wrote:
On 05.03.2026 20:57, Ayan Kumar Halder wrote:
--- a/xen/arch/arm/include/asm/gic.h
+++ b/xen/arch/arm/include/asm/gic.h
@@ -237,7 +237,15 @@ enum gic_version {
GIC_V3,
};
+/*
+ * GICv3 supports up to 16 LRs (4 bits in ICH_VTR_EL2), can use uint16_t
+ * GICv2 supports up to 64 LRs (6 bits in GICH_VTR), requires uint64_t
+ */
+#ifdef CONFIG_GICV3
+DECLARE_PER_CPU(uint16_t, lr_mask);
+#else
DECLARE_PER_CPU(uint64_t, lr_mask);
+#endif
But GICV2 and GICV3 can be enabled at the same time, at which point you'd still
need 64 bits, I suppose.
I see. However, a safety certified Xen which is meant to support GICv3
hardware, will only have GICv3 enabled.
IOW having both GICV2 =y && GICV2 = y is out of scope for the safety use
cases.
- Ayan
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