[Xen-devel] [PATCH v2 10/13] libx86: introduce a helper to deserialise msr_policy objects

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

From: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>

v2:
 * Rebase over the msr_{domain,vcpu}_policy rename
 * Only deserialse msr_policy
 * Expand boundary justifications
---
 xen/common/libx86/msr.c      | 51 ++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/libx86/msr.h | 10 +++++++++
 2 files changed, 61 insertions(+)

diff --git a/xen/common/libx86/msr.c b/xen/common/libx86/msr.c
index 71c8e9a..0912ace 100644
--- a/xen/common/libx86/msr.c
+++ b/xen/common/libx86/msr.c
@@ -45,6 +45,57 @@ int x86_msr_copy_to_buffer(const struct msr_policy *p,
     return 0;
 }
 
+int x86_msr_copy_from_buffer(struct msr_policy *p,
+                             const msr_entry_buffer_t msrs, uint32_t nr_msrs,
+                             uint32_t *err_msr)
+{
+    unsigned int i;
+    xen_msr_entry_t data;
+
+    /*
+     * A well formed caller is expected pass an array with entries in order,
+     * and without any repetitions.  However, due to per-vendor differences,
+     * and in the case of upgrade or levelled scenarios, we typically expect
+     * fewer than MAX entries to be passed.
+     *
+     * Detecting repeated entries is prohibitively complicated, so we don't
+     * bother.  That said, one way or another if more than MAX entries are
+     * passed, something is wrong.
+     */
+    if ( nr_msrs > MSR_MAX_SERIALISED_ENTRIES )
+        return -E2BIG;
+
+    for ( i = 0; i < nr_msrs; i++ )
+    {
+        if ( copy_from_buffer_offset(&data, msrs, i, 1) )
+            return -EFAULT;
+
+        if ( data.flags ) /* .flags MBZ */
+            goto err;
+
+        switch ( data.idx )
+        {
+        case MSR_INTEL_PLATFORM_INFO:
+            if ( data.val > ~0u )
+                goto err;
+
+            p->plaform_info.raw = data.val;
+            break;
+
+        default:
+            goto err;
+        }
+    }
+
+    return 0;
+
+ err:
+    if ( err_msr )
+        *err_msr = data.idx;
+
+    return -EINVAL;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/xen/libx86/msr.h b/xen/include/xen/libx86/msr.h
index 2e4acd4..d71ad78 100644
--- a/xen/include/xen/libx86/msr.h
+++ b/xen/include/xen/libx86/msr.h
@@ -42,6 +42,16 @@ typedef xen_msr_entry_t msr_entry_buffer_t[];
 int x86_msr_copy_to_buffer(const struct msr_policy *p,
                            msr_entry_buffer_t msrs, uint32_t *nr_entries_p);
 
+/*
+ * Copy MSR data from a buffer, filling an msr_policy object.  MSR indicies
+ * are checked for being in range, but no content validation is performed for
+ * in-range MSRs.  On an error, the optional err_* pointer may help identify
+ * where the issue lies.
+ */
+int x86_msr_copy_from_buffer(struct msr_policy *dp,
+                             const msr_entry_buffer_t msrs, uint32_t nr_msrs,
+                             uint32_t *err_msr);
+
 #endif /* !XEN_LIBX86_MSR_H */
 
 /*
-- 
2.1.4


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