[PATCH] xen/arm: Hide PMU feature

[Hirokazu Takahashi <taka@xxxxxxxxxxxxx>]

On ARMv8.4-A and newer platforms, booting Dom0 Linux with ACPI enabled
causes the domain to probe advanced PMU feature based on system ID
register ID_AA64DFR0_EL1.

During this probe, Linux accesses PMMIR_EL1, which causes unhandled
register traps and crashes the domain. Merely adding emulation code
for PMMIR_EL1 in Xen is insufficient to fix the issue, as the guest
PMU driver subsequently stalls during its initialization sequence.

Fix this by explicitly masking PMU capability fields in
create_domain_cpuinfo(). Additionally, preemptively mask other
capability fields to prevent similar potential issues.

Fixes: 3669a1cb9598 "xen/arm: create a cpuinfo structure for guest"
Signed-off-by: Hirokazu Takahashi <taka@xxxxxxxxxxxxx>
---
 xen/arch/arm/cpufeature.c             | 16 ++++++++++++++++
 xen/arch/arm/include/asm/cpufeature.h | 10 ++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
index 94d14fb6a9..71d745d3cb 100644
--- a/xen/arch/arm/cpufeature.c
+++ b/xen/arch/arm/cpufeature.c
@@ -219,8 +219,24 @@ static int __init create_domain_cpuinfo(void)
     domain_cpuinfo.isa64.api = 0;
     domain_cpuinfo.isa64.gpa = 0;
     domain_cpuinfo.isa64.gpi = 0;
+
+    /* Hide PMUv3 support as Xen does not support it */
+    domain_cpuinfo.dbg64.pmu_ver = 0;
+    domain_cpuinfo.dbg64.mtpmu = 0;
+    domain_cpuinfo.dbg64.pmss = 0;
+
+    /* Hide SPE, TRBE, BRBE, and Trace Extensions */
+    domain_cpuinfo.dbg64.pms_ver = 0;
+    domain_cpuinfo.dbg64.trace_ver = 0;
+    domain_cpuinfo.dbg64.trace_filt = 0;
+    domain_cpuinfo.dbg64.trace_buffer = 0;
+    domain_cpuinfo.dbg64.ext_trc_buff = 0;
+    domain_cpuinfo.dbg64.brbe = 0;
 #endif
 
+    /* Hide PMUv1,v2 support as Xen does not support it */
+    domain_cpuinfo.dbg32.perfmon = 0;
+
     /* Hide AMU support */
 #ifdef CONFIG_ARM_64
     domain_cpuinfo.pfr64.amu = 0;
diff --git a/xen/arch/arm/include/asm/cpufeature.h 
b/xen/arch/arm/include/asm/cpufeature.h
index bf902a3970..c92b2651c7 100644
--- a/xen/arch/arm/include/asm/cpufeature.h
+++ b/xen/arch/arm/include/asm/cpufeature.h
@@ -216,16 +216,18 @@ struct cpuinfo_arm {
             unsigned long trace_ver:4;
             unsigned long pmu_ver:4;
             unsigned long brps:4;
-            unsigned long __res0:4;
+            unsigned long pmss:4;
             unsigned long wrps:4;
-            unsigned long __res1:4;
+            unsigned long sebep:4;
             unsigned long ctx_cmps:4;
             unsigned long pms_ver:4;
             unsigned long double_lock:4;
             unsigned long trace_filt:4;
-            unsigned long __res2:4;
+            unsigned long trace_buffer:4;
             unsigned long mtpmu:4;
-            unsigned long __res3:12;
+            unsigned long brbe:4;
+            unsigned long ext_trc_buff:4;
+            unsigned long hpmn0:4;
 
             /* DFR1 */
             unsigned long __res4:64;
-- 
2.43.0