diff mbox

[RFC,v1,1/2] utils: Add helper to read arm MIDR_EL1 register

Message ID 1470133216-6758-2-git-send-email-vijay.kilari@gmail.com
State New
Headers show

Commit Message

Vijay Kilari Aug. 2, 2016, 10:20 a.m. UTC 
From: Vijaya Kumar K <Vijaya.Kumar@cavium.com>


Add helper API to read MIDR_EL1 registers to fetch
cpu identification information. This helps in
adding errata's and architecture specific features.

This is implemented only for arm architecture.

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@cavium.com>

---
 include/qemu-common.h |    1 +
 util/Makefile.objs    |    1 +
 util/cpuinfo.c        |   52 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+)

-- 
1.7.9.5

Comments

Peter Maydell Aug. 2, 2016, 11:10 a.m. UTC | #1 
On 2 August 2016 at 11:20,  <vijay.kilari@gmail.com> wrote:
> +long int qemu_read_cpuid_info(void)


Don't use "long" here, it might be 32 or 64 bits.
The kernel ABI for the /sys/ file we're reading says it
is a 64-bit value, so uint64_t is what you want.

> +{

> +    FILE *fp;

> +    char *buf;

> +    long int midr = 0;

> +#define BUF_SIZE 32

> +

> +    fp = fopen("/sys/devices/system/cpu/cpu0/regs/identification/midr_el1",

> +               "r");

> +    if (!fp) {

> +        return 0;

> +    }

> +

> +    buf = g_malloc0(BUF_SIZE);

> +    if (!buf) {

> +        fclose(fp);

> +        return 0;

> +    }

> +

> +    if (buf != fgets(buf, BUF_SIZE - 1, fp)) {

> +        goto out;

> +    }


g_file_get_contents() is probably easier than manually
opening the file and reading it into an allocated buffer.

> +

> +    if (qemu_strtol(buf, NULL, 0, &midr) < 0) {


qemu_strtoull().

> +        goto out;

> +    }

> +

> +out:

> +    g_free(buf);

> +    fclose(fp);

> +

> +    return midr;

> +}

> +#endif

> --

> 1.7.9.5

>


thanks
-- PMM
diff mbox

Patch

diff --git a/include/qemu-common.h b/include/qemu-common.h
index 1f2cb94..62ad674 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -134,4 +134,5 @@  void page_size_init(void);
  * returned. */
 bool dump_in_progress(void);
 
+long int qemu_read_cpuid_info(void);
 #endif
diff --git a/util/Makefile.objs b/util/Makefile.objs
index 96cb1e0..9d25a72 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -35,3 +35,4 @@  util-obj-y += log.o
 util-obj-y += qdist.o
 util-obj-y += qht.o
 util-obj-y += range.o
+util-obj-y += cpuinfo.o
diff --git a/util/cpuinfo.c b/util/cpuinfo.c
new file mode 100644
index 0000000..3ba7194
--- /dev/null
+++ b/util/cpuinfo.c
@@ -0,0 +1,52 @@ 
+/*
+ * Dealing with arm cpu identification information.
+ *
+ * Copyright (C) 2016 Cavium, Inc.
+ *
+ * Authors:
+ *  Vijaya Kumar K <Vijaya.Kumar@cavium.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1
+ * or later.  See the COPYING.LIB file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "qemu/cutils.h"
+
+#if defined(__aarch64__)
+
+long int qemu_read_cpuid_info(void)
+{
+    FILE *fp;
+    char *buf;
+    long int midr = 0;
+#define BUF_SIZE 32
+
+    fp = fopen("/sys/devices/system/cpu/cpu0/regs/identification/midr_el1",
+               "r");
+    if (!fp) {
+        return 0;
+    }
+
+    buf = g_malloc0(BUF_SIZE);
+    if (!buf) {
+        fclose(fp);
+        return 0;
+    }
+
+    if (buf != fgets(buf, BUF_SIZE - 1, fp)) {
+        goto out;
+    }
+
+    if (qemu_strtol(buf, NULL, 0, &midr) < 0) {
+        goto out;
+    }
+
+out:
+    g_free(buf);
+    fclose(fp);
+
+    return midr;
+}
+#endif