[PATCH v2 08/13] libx86: Introduce a helper to serialise msr_policy objects

[Andrew Cooper <andrew.cooper3@citrix.com>]

From: Roger Pau Monné <roger.pau@citrix.com>

As with CPUID, an architectural form is used for representing the MSR data.
It is expected not to change moving forwards, but does have a 32 bit field
(currently reserved) which can be used compatibly if needs be.

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

v2:
 * Rebase over the msr_{domain,vcpu}_policy rename
 * Only serialise msr_policy
 * Change to an array typedef for constness reasons
---
 tools/libxc/Makefile              |  2 +-
 xen/common/libx86/Makefile        |  1 +
 xen/common/libx86/msr.c           | 56 +++++++++++++++++++++++++++++++++++++++
 xen/common/libx86/private.h       |  3 +++
 xen/include/public/arch-x86/xen.h |  9 ++++++-
 xen/include/xen/libx86/msr.h      | 20 ++++++++++++++
 6 files changed, 89 insertions(+), 2 deletions(-)
 create mode 100644 xen/common/libx86/msr.c

diff --git a/tools/libxc/Makefile b/tools/libxc/Makefile
index cd4225c..904e026 100644
--- a/tools/libxc/Makefile
+++ b/tools/libxc/Makefile
@@ -83,7 +83,7 @@ $(patsubst %.c,%.opic,$(ELF_SRCS-y)): CFLAGS += -Wno-pointer-sign
 ifeq ($(CONFIG_X86),y) # Add libx86 to the build
 vpath %.c ../../xen/common/libx86
 
-GUEST_SRCS-y                 += cpuid.c
+GUEST_SRCS-y                 += cpuid.c msr.c
 endif
 
 # new domain builder
diff --git a/xen/common/libx86/Makefile b/xen/common/libx86/Makefile
index 3fb2e0b..2f9691e 100644
--- a/xen/common/libx86/Makefile
+++ b/xen/common/libx86/Makefile
@@ -1 +1,2 @@
 obj-y += cpuid.o
+obj-y += msr.o
diff --git a/xen/common/libx86/msr.c b/xen/common/libx86/msr.c
new file mode 100644
index 0000000..71c8e9a
--- /dev/null
+++ b/xen/common/libx86/msr.c
@@ -0,0 +1,56 @@
+#include "private.h"
+
+#include <xen/libx86/msr.h>
+
+/*
+ * Copy a single MSR into the provided msr_entry_buffer_t buffer, performing a
+ * boundary check against the buffer size.
+ */
+static int copy_msr_to_buffer(uint32_t idx, uint64_t val,
+                              msr_entry_buffer_t msrs,
+                              uint32_t *curr_entry, const uint32_t nr_entries)
+{
+    const xen_msr_entry_t ent = { .idx = idx, .val = val };
+
+    if ( *curr_entry == nr_entries )
+        return -ENOBUFS;
+
+    if ( copy_to_buffer_offset(msrs, *curr_entry, &ent, 1) )
+        return -EFAULT;
+
+    ++*curr_entry;
+
+    return 0;
+}
+
+int x86_msr_copy_to_buffer(const struct msr_policy *p,
+                           msr_entry_buffer_t msrs, uint32_t *nr_entries_p)
+{
+    const uint32_t nr_entries = *nr_entries_p;
+    uint32_t curr_entry = 0;
+
+#define COPY_MSR(idx, val)                                      \
+    ({  int ret;                                                \
+        if ( (ret = copy_msr_to_buffer(                         \
+                  idx, val, msrs, &curr_entry, nr_entries)) )   \
+            return ret;                                         \
+    })
+
+    COPY_MSR(MSR_INTEL_PLATFORM_INFO, p->plaform_info.raw);
+
+#undef COPY_MSR
+
+    *nr_entries_p = curr_entry;
+
+    return 0;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/common/libx86/private.h b/xen/common/libx86/private.h
index 5f59961..e874fb6 100644
--- a/xen/common/libx86/private.h
+++ b/xen/common/libx86/private.h
@@ -9,6 +9,7 @@
 #include <xen/types.h>
 
 #include <asm/guest_access.h>
+#include <asm/msr-index.h>
 
 #define copy_to_buffer_offset copy_to_guest_offset
 
@@ -19,6 +20,8 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+#include <xen/asm/msr-index.h>
+
 #include <xen-tools/libs.h>
 
 static inline bool test_bit(unsigned int bit, const void *vaddr)
diff --git a/xen/include/public/arch-x86/xen.h b/xen/include/public/arch-x86/xen.h
index f3bdd83..55a149f 100644
--- a/xen/include/public/arch-x86/xen.h
+++ b/xen/include/public/arch-x86/xen.h
@@ -315,7 +315,7 @@ struct xen_arch_domainconfig {
 #endif
 
 /*
- * Representations of architectural CPUID information.  Used as the
+ * Representations of architectural CPUID and MSR information.  Used as the
  * serialised version of Xen's internal representation.
  */
 typedef struct xen_cpuid_leaf {
@@ -325,6 +325,13 @@ typedef struct xen_cpuid_leaf {
 } xen_cpuid_leaf_t;
 DEFINE_XEN_GUEST_HANDLE(xen_cpuid_leaf_t);
 
+typedef struct xen_msr_entry {
+    uint32_t idx;
+    uint32_t flags; /* Reserved MBZ. */
+    uint64_t val;
+} xen_msr_entry_t;
+DEFINE_XEN_GUEST_HANDLE(xen_msr_entry_t);
+
 #endif /* !__ASSEMBLY__ */
 
 /*
diff --git a/xen/include/xen/libx86/msr.h b/xen/include/xen/libx86/msr.h
index b8b1751..2e4acd4 100644
--- a/xen/include/xen/libx86/msr.h
+++ b/xen/include/xen/libx86/msr.h
@@ -2,6 +2,9 @@
 #ifndef XEN_LIBX86_MSR_H
 #define XEN_LIBX86_MSR_H
 
+/* Maximum number of MSRs written when serialising msr_domain_policy. */
+#define MSR_MAX_SERIALISED_ENTRIES 1
+
 /* MSR policy object for shared per-domain MSRs */
 struct msr_policy
 {
@@ -22,6 +25,23 @@ struct msr_policy
     } plaform_info;
 };
 
+#ifdef __XEN__
+#include <public/arch-x86/xen.h>
+typedef XEN_GUEST_HANDLE_64(xen_msr_entry_t) msr_entry_buffer_t;
+#else
+#include <xen/arch-x86/xen.h>
+typedef xen_msr_entry_t msr_entry_buffer_t[];
+#endif
+
+/*
+ * Serialise a msr_policy object into an array.  Writes at most
+ * MSR_MAX_SERIALISED_ENTRIES.  Returns -ENOBUFS if the buffer array is too
+ * short.  On success, nr_entries_p is updated with the actual number of
+ * leaves written.
+ */
+int x86_msr_copy_to_buffer(const struct msr_policy *p,
+                           msr_entry_buffer_t msrs, uint32_t *nr_entries_p);
+
 #endif /* !XEN_LIBX86_MSR_H */
 
 /*
-- 
2.1.4


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