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Subject[PATCH 3.2 035/104] x86: Add another set of MSR accessor functions
3.2.101-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Borislav Petkov <bp@suse.de>

commit 22085a66c2fab6cf9b9393c056a3600a6b4735de upstream.

We very often need to set or clear a bit in an MSR as a result of doing
some sort of a hardware configuration. Add generic versions of that
repeated functionality in order to save us a bunch of duplicated code in
the early CPU vendor detection/config code.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1394384725-10796-2-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
[bwh: Backported to 3.2: s/wrmsrl_safe/checking_wrmsrl/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/include/asm/msr.h | 2 ++
arch/x86/lib/msr.c | 89 +++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 90 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -265,6 +265,8 @@ do {

struct msr *msrs_alloc(void);
void msrs_free(struct msr *msrs);
+int msr_set_bit(u32 msr, u8 bit);
+int msr_clear_bit(u32 msr, u8 bit);

#ifdef CONFIG_SMP
int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
--- a/arch/x86/lib/msr.c
+++ b/arch/x86/lib/msr.c
@@ -8,7 +8,7 @@ struct msr *msrs_alloc(void)

msrs = alloc_percpu(struct msr);
if (!msrs) {
- pr_warning("%s: error allocating msrs\n", __func__);
+ pr_warn("%s: error allocating msrs\n", __func__);
return NULL;
}

@@ -21,3 +21,90 @@ 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 checking_wrmsrl(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, &m);
+ 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);
+}
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