[Xen-devel] [PATCH v6 3/7] xen/arm: Detect silicon revision and set cap bits accordingly

[Julien Grall <julien.grall@xxxxxxx>]

After each CPU has been started, we iterate through a list of CPU
errata to detect CPUs which need from hypervisor code patches.

For each bug there is a function which checks if that a particular CPU is
affected. This needs to be done on every CPU to cover heterogenous
systems properly.

If a certain erratum has been detected, the capability bit will be set.
In the case the erratum requires code patching, this will be triggered
by the call to apply_alternatives.

The code is based on the file arch/arm64/kernel/cpu_errata.c in Linux
v4.6-rc3.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
    Changes in v6:
        - Fix typoes in the commit message
        - Add __ to the guard

    Changes in v4:
        - Add missing emacs magic blocks
        - Add Stefano's acked-by

    Changes in v3:
        - Move update_cpu_capabilities in a separate patch
        - Update the commit message to mention that workaround may
        not require code patching.

    Changes in v2:
        - Use XENLOG_INFO for the loglevel of the message
---
 xen/arch/arm/Makefile            |  1 +
 xen/arch/arm/cpuerrata.c         | 34 ++++++++++++++++++++++++++++++++++
 xen/arch/arm/setup.c             |  3 +++
 xen/arch/arm/smpboot.c           |  3 +++
 xen/include/asm-arm/cpuerrata.h  | 14 ++++++++++++++
 xen/include/asm-arm/cpufeature.h |  6 ++++++
 6 files changed, 61 insertions(+)
 create mode 100644 xen/arch/arm/cpuerrata.c
 create mode 100644 xen/include/asm-arm/cpuerrata.h

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 74bd7b8..23aaf52 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -7,6 +7,7 @@ subdir-$(CONFIG_ACPI) += acpi
 obj-$(CONFIG_ALTERNATIVE) += alternative.o
 obj-y += bootfdt.o
 obj-y += cpu.o
+obj-y += cpuerrata.o
 obj-y += cpufeature.o
 obj-y += decode.o
 obj-y += device.o
diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
new file mode 100644
index 0000000..03ae7b4
--- /dev/null
+++ b/xen/arch/arm/cpuerrata.c
@@ -0,0 +1,34 @@
+#include <xen/config.h>
+#include <asm/cpufeature.h>
+#include <asm/cpuerrata.h>
+
+#define MIDR_RANGE(model, min, max)     \
+    .matches = is_affected_midr_range,  \
+    .midr_model = model,                \
+    .midr_range_min = min,              \
+    .midr_range_max = max
+
+static bool_t __maybe_unused
+is_affected_midr_range(const struct arm_cpu_capabilities *entry)
+{
+    return MIDR_IS_CPU_MODEL_RANGE(boot_cpu_data.midr.bits, entry->midr_model,
+                                   entry->midr_range_min,
+                                   entry->midr_range_max);
+}
+
+static const struct arm_cpu_capabilities arm_errata[] = {
+    {},
+};
+
+void check_local_cpu_errata(void)
+{
+    update_cpu_capabilities(arm_errata, "enabled workaround for");
+}
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 97b3214..38eb888 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -43,6 +43,7 @@
 #include <asm/current.h>
 #include <asm/setup.h>
 #include <asm/gic.h>
+#include <asm/cpuerrata.h>
 #include <asm/cpufeature.h>
 #include <asm/platform.h>
 #include <asm/procinfo.h>
@@ -171,6 +172,8 @@ static void __init processor_id(void)
     }
 
     processor_setup();
+
+    check_local_cpu_errata();
 }
 
 void dt_unreserved_regions(paddr_t s, paddr_t e,
diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 3a962f7..d56b91d 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -29,6 +29,7 @@
 #include <xen/timer.h>
 #include <xen/irq.h>
 #include <xen/console.h>
+#include <asm/cpuerrata.h>
 #include <asm/gic.h>
 #include <asm/psci.h>
 #include <asm/acpi.h>
@@ -316,6 +317,8 @@ void start_secondary(unsigned long boot_phys_offset,
     local_irq_enable();
     local_abort_enable();
 
+    check_local_cpu_errata();
+
     printk(XENLOG_DEBUG "CPU %u booted.\n", smp_processor_id());
 
     startup_cpu_idle_loop();
diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h
new file mode 100644
index 0000000..c495ee5
--- /dev/null
+++ b/xen/include/asm-arm/cpuerrata.h
@@ -0,0 +1,14 @@
+#ifndef __ARM_CPUERRATA_H__
+#define __ARM_CPUERRATA_H__
+
+void check_local_cpu_errata(void);
+
+#endif /* __ARM_CPUERRATA_H__ */
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h
index be2414c..fb57295 100644
--- a/xen/include/asm-arm/cpufeature.h
+++ b/xen/include/asm-arm/cpufeature.h
@@ -66,6 +66,12 @@ struct arm_cpu_capabilities {
     const char *desc;
     u16 capability;
     bool_t (*matches)(const struct arm_cpu_capabilities *);
+    union {
+        struct {    /* To be used for eratum handling only */
+            u32 midr_model;
+            u32 midr_range_min, midr_range_max;
+        };
+    };
 };
 
 void update_cpu_capabilities(const struct arm_cpu_capabilities *caps,
-- 
1.9.1


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