xen/arm: remove XEN_DOMCTL_CONFIG_GIC_NATIVE from the ABI

Now that the toolstack always resolves a concrete GIC_V2 or GIC_V3
before calling createdomain, nothing on the Xen side needs to resolve
GIC_NATIVE either:

 * A new gic_domctl_hw_version() helper returns the
   XEN_DOMCTL_CONFIG_GIC_* value matching the host's gic_hw_version().
 * arch_sanitise_domain_config() uses it to validate the requested
   version against the hardware, rather than resolving GIC_NATIVE and
   writing the result back into config->arch.gic_version. A guest must
   use the host's GIC version, except that a GICv3 host with the GICv2
   compatibility mode enabled may also run GICv2 guests. This is the
   same information that XEN_SYSCTL_physinfo reports to the toolstack.
 * create_dom0() and arch_parse_dom0less_node(), which both always want
   a vGIC that exactly matches the hardware, use the same helper instead
   of GIC_NATIVE.

With nothing left resolving or relying on it, drop
XEN_DOMCTL_CONFIG_GIC_NATIVE from the public ABI. Every caller must now
request a concrete GIC_V2 or GIC_V3.

This is an incompatible change for any toolstack still passing 0
(formerly GIC_NATIVE) expecting Xen to auto-select a version. Add a
CHANGELOG.md entry, noting that available GIC versions can be queried
via XEN_SYSCTL_physinfo.

Signed-off-by: Julian Vetter <julian.vetter@vates.tech>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

CHANGELOG.md

@@ -18,6 +18,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Added
 
 ### Removed
+ - On Arm:
+   - XEN_DOMCTL_CONFIG_GIC_NATIVE has been removed. Toolstacks must now
+     explicitly request GIC_V2 or GIC_V3 when creating a domain.
+     Available GIC versions can be queried via XEN_SYSCTL_physinfo.
  - On x86:
    - The kexec "v1" interface, which was declared obsolete in Xen 4.4 (2013).
      The only known user was the classic-xen fork of Linux.  This does not

xen/arch/arm/dom0less-build.c

@@ -23,6 +23,7 @@
 #include <asm/arm64/sve.h>
 #include <asm/domain_build.h>
 #include <asm/firmware/sci.h>
+#include <asm/gic.h>
 #include <asm/grant_table.h>
 #include <asm/setup.h>
 
@@ -368,7 +369,7 @@ int __init arch_parse_dom0less_node(struct dt_device_node *node,
     unsigned int flags = bd->create_flags;
     uint32_t val;
 
-    d_cfg->arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE;
+    d_cfg->arch.gic_version = gic_domctl_hw_version();
     d_cfg->flags |= XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap;
 
     if ( domu_dt_sci_parse(node, d_cfg) )

xen/arch/arm/domain.c

@@ -609,23 +609,18 @@ int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
         return -EINVAL;
     }
 
-    /* Fill in the native GIC version, passed back to the toolstack. */
-    if ( config->arch.gic_version == XEN_DOMCTL_CONFIG_GIC_NATIVE )
+    /*
+     * A guest can only use the host's GIC version, except that a GICv3 host
+     * with the GICv2 compatibility mode enabled can also run GICv2 guests.
+     * This mirrors what XEN_SYSCTL_physinfo reports to the toolstack.
+     */
+    if ( config->arch.gic_version != gic_domctl_hw_version() &&
+         !(config->arch.gic_version == XEN_DOMCTL_CONFIG_GIC_V2 &&
+           vgic_v2_hw_enabled()) )
     {
-        switch ( gic_hw_version() )
-        {
-        case GIC_V2:
-            config->arch.gic_version = XEN_DOMCTL_CONFIG_GIC_V2;
-            break;
-
-        case GIC_V3:
-            config->arch.gic_version = XEN_DOMCTL_CONFIG_GIC_V3;
-            break;
-
-        default:
-            ASSERT_UNREACHABLE();
-            return -EINVAL;
-        }
+        dprintk(XENLOG_INFO, "Unsupported GIC version %u\n",
+                config->arch.gic_version);
+        return -EINVAL;
     }
 
     /* max_vcpus depends on the GIC version, and Xen's compiled limit. */
@@ -634,6 +629,7 @@ int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
     if ( max_vcpus == 0 )
     {
         dprintk(XENLOG_INFO, "Unsupported GIC version\n");
+        ASSERT_UNREACHABLE();
         return -EINVAL;
     }
 

xen/arch/arm/domain_build.c

@@ -26,6 +26,7 @@
 #include <xen/warning.h>
 #include <xen/static-shmem.h>
 #include <asm/device.h>
+#include <asm/gic.h>
 #include <asm/setup.h>
 #include <asm/tee/tee.h>
 #include <asm/pci.h>
@@ -1967,7 +1968,7 @@ void __init create_dom0(void)
     int rc;
 
     /* The vGIC for DOM0 is exactly emulating the hardware GIC */
-    dom0_cfg.arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE;
+    dom0_cfg.arch.gic_version = gic_domctl_hw_version();
     dom0_cfg.arch.nr_spis = vgic_def_nr_spis();
     dom0_cfg.arch.tee_type = tee_get_type();
     dom0_cfg.max_vcpus = dom0_max_vcpus();

xen/arch/arm/gic.c

@@ -56,6 +56,21 @@ enum gic_version gic_hw_version(void)
    return gic_hw_ops->info->hw_version;
 }
 
+uint8_t gic_domctl_hw_version(void)
+{
+    switch ( gic_hw_version() )
+    {
+    case GIC_V2:
+        return XEN_DOMCTL_CONFIG_GIC_V2;
+
+    case GIC_V3:
+        return XEN_DOMCTL_CONFIG_GIC_V3;
+
+    default:
+        BUG();
+    }
+}
+
 unsigned int gic_number_lines(void)
 {
     return gic_hw_ops->info->nr_lines;

xen/arch/arm/include/asm/gic.h

@@ -262,6 +262,12 @@ DECLARE_PER_CPU(uint64_t, lr_mask);
 
 extern enum gic_version gic_hw_version(void);
 
+/*
+ * The XEN_DOMCTL_CONFIG_GIC_* value matching the GIC version actually
+ * present on this host.
+ */
+uint8_t gic_domctl_hw_version(void);
+
 /* Program the IRQ type into the GIC */
 void gic_set_irq_type(struct irq_desc *desc, unsigned int type);
 

xen/include/public/arch-arm.h

@@ -319,7 +319,7 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_guest_context_t);
  * struct xen_arch_domainconfig's ABI is covered by
  * XEN_DOMCTL_INTERFACE_VERSION.
  */
-#define XEN_DOMCTL_CONFIG_GIC_NATIVE    0
+/*      XEN_DOMCTL_CONFIG_GIC_NATIVE    0 - removed in Xen 4.23 */
 #define XEN_DOMCTL_CONFIG_GIC_V2        1
 #define XEN_DOMCTL_CONFIG_GIC_V3        2
 
@@ -335,7 +335,7 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_guest_context_t);
 #define XEN_DOMCTL_CONFIG_ARM_V8R_EL1_MSA_VMSA    2
 
 struct xen_arch_domainconfig {
-    /* IN/OUT */
+    /* IN */
     uint8_t gic_version;
     /* IN - Contains SVE vector length divided by 128 */
     uint8_t sve_vl;