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-rw-r--r--arch/x86/lib/msr.c110
1 files changed, 110 insertions, 0 deletions
diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
new file mode 100644
index 000000000..43623739c
--- /dev/null
+++ b/arch/x86/lib/msr.c
@@ -0,0 +1,110 @@
+#include <linux/module.h>
+#include <linux/preempt.h>
+#include <asm/msr.h>
+
+struct msr *msrs_alloc(void)
+{
+ struct msr *msrs = NULL;
+
+ msrs = alloc_percpu(struct msr);
+ if (!msrs) {
+ pr_warn("%s: error allocating msrs\n", __func__);
+ return NULL;
+ }
+
+ return msrs;
+}
+EXPORT_SYMBOL(msrs_alloc);
+
+void msrs_free(struct msr *msrs)
+{
+ free_percpu(msrs);
+}
+EXPORT_SYMBOL(msrs_free);
+
+/**
+ * Read an MSR with error handling
+ *
+ * @msr: MSR to read
+ * @m: value to read into
+ *
+ * It returns read data only on success, otherwise it doesn't change the output
+ * argument @m.
+ *
+ */
+int msr_read(u32 msr, struct msr *m)
+{
+ int err;
+ u64 val;
+
+ err = rdmsrl_safe(msr, &val);
+ if (!err)
+ m->q = val;
+
+ return err;
+}
+
+/**
+ * Write an MSR with error handling
+ *
+ * @msr: MSR to write
+ * @m: value to write
+ */
+int msr_write(u32 msr, struct msr *m)
+{
+ return wrmsrl_safe(msr, m->q);
+}
+
+static inline int __flip_bit(u32 msr, u8 bit, bool set)
+{
+ struct msr m, m1;
+ int err = -EINVAL;
+
+ if (bit > 63)
+ return err;
+
+ err = msr_read(msr, &m);
+ if (err)
+ return err;
+
+ m1 = m;
+ if (set)
+ m1.q |= BIT_64(bit);
+ else
+ m1.q &= ~BIT_64(bit);
+
+ if (m1.q == m.q)
+ return 0;
+
+ err = msr_write(msr, &m1);
+ if (err)
+ return err;
+
+ return 1;
+}
+
+/**
+ * Set @bit in a MSR @msr.
+ *
+ * Retval:
+ * < 0: An error was encountered.
+ * = 0: Bit was already set.
+ * > 0: Hardware accepted the MSR write.
+ */
+int msr_set_bit(u32 msr, u8 bit)
+{
+ return __flip_bit(msr, bit, true);
+}
+
+/**
+ * Clear @bit in a MSR @msr.
+ *
+ * Retval:
+ * < 0: An error was encountered.
+ * = 0: Bit was already cleared.
+ * > 0: Hardware accepted the MSR write.
+ */
+int msr_clear_bit(u32 msr, u8 bit)
+{
+ return __flip_bit(msr, bit, false);
+}