xen/arm: create a cpuinfo structure for guest

Create a cpuinfo structure for guest and mask into it the features that
we do not support in Xen or that we do not want to publish to guests.

Modify some values in the cpuinfo structure for guests to mask some
features which we do not want to allow to guests (like AMU) or we do not
support (like SVE).
Modify some values in the guest cpuinfo structure to guests to hide some
processor features:
- SVE as this is not supported by Xen and guest are not allowed to use
this features (ZEN is set to 0 in CPTR_EL2).
- AMU as HCPTR_TAM is set in CPTR_EL2 so AMU cannot be used by guests
All other bits are left untouched.
- RAS as this is not supported by Xen.

The code is trying to group together registers modifications for the
same feature to be able in the long term to easily enable/disable a
feature depending on user parameters or add other registers modification
in the same place (like enabling/disabling HCR bits).

Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
index 86b99ee96051a7ad0bf00abc1cde69ef7f01ea2c..1f6a85aafe2a7063cc7014a9072ea1bedc553e60 100644 (file)
--- a/xen/arch/arm/cpufeature.c
+++ b/xen/arch/arm/cpufeature.c
@@ -24,6 +24,8 @@
 
 DECLARE_BITMAP(cpu_hwcaps, ARM_NCAPS);
 
+struct cpuinfo_arm __read_mostly guest_cpuinfo;
+
 void update_cpu_capabilities(const struct arm_cpu_capabilities *caps,
                              const char *info)
 {
@@ -151,6 +153,55 @@ void identify_cpu(struct cpuinfo_arm *c)
         c->mvfr.bits[2] = READ_SYSREG(MVFR2_EL1);
 }
 
+/*
+ * This function is creating a cpuinfo structure with values modified to mask
+ * all cpu features that should not be published to guest.
+ * The created structure is then used to provide ID registers values to guests.
+ */
+static int __init create_guest_cpuinfo(void)
+{
+    /*
+     * TODO: The code is currently using only the features detected on the boot
+     * core. In the long term we should try to compute values containing only
+     * features supported by all cores.
+     */
+    guest_cpuinfo = boot_cpu_data;
+
+#ifdef CONFIG_ARM_64
+    /* Hide MPAM support as xen does not support it */
+    guest_cpuinfo.pfr64.mpam = 0;
+    guest_cpuinfo.pfr64.mpam_frac = 0;
+
+    /* Hide SVE as Xen does not support it */
+    guest_cpuinfo.pfr64.sve = 0;
+    guest_cpuinfo.zfr64.bits[0] = 0;
+
+    /* Hide MTE support as Xen does not support it */
+    guest_cpuinfo.pfr64.mte = 0;
+#endif
+
+    /* Hide AMU support */
+#ifdef CONFIG_ARM_64
+    guest_cpuinfo.pfr64.amu = 0;
+#endif
+    guest_cpuinfo.pfr32.amu = 0;
+
+    /* Hide RAS support as Xen does not support it */
+#ifdef CONFIG_ARM_64
+    guest_cpuinfo.pfr64.ras = 0;
+    guest_cpuinfo.pfr64.ras_frac = 0;
+#endif
+    guest_cpuinfo.pfr32.ras = 0;
+    guest_cpuinfo.pfr32.ras_frac = 0;
+
+    return 0;
+}
+/*
+ * This function needs to be run after all smp are started to have
+ * cpuinfo structures for all cores.
+ */
+__initcall(create_guest_cpuinfo);
+
 /*
  * Local variables:
  * mode: C

diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index 74139be1cc8c3e100d86341141ab3c9a08a965e1..6058744c185c908c2718d6c783fede37c71348b4 100644 (file)
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -283,6 +283,8 @@ extern void identify_cpu(struct cpuinfo_arm *);
 extern struct cpuinfo_arm cpu_data[];
 #define current_cpu_data cpu_data[smp_processor_id()]
 
+extern struct cpuinfo_arm guest_cpuinfo;
+
 #endif /* __ASSEMBLY__ */
 
 #endif