[Xen-devel] [PATCH 4/5] common/domain: add a domain context record for shared_info...

[Paul Durrant <paul@xxxxxxx>]

... and update xen-ctx to dump some information describing the record.

NOTE: To allow a sensible definition of the record in public/save.h
      this patch also adds a definition of the Xen ABI's de-facto page
      size into public/xen.h.

Signed-off-by: Paul Durrant <paul@xxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Julien Grall <julien@xxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 tools/misc/xen-ctx.c      |  8 ++++++
 xen/common/domain.c       | 55 +++++++++++++++++++++++++++++++++++++++
 xen/include/public/save.h | 10 ++++++-
 xen/include/public/xen.h  |  3 +++
 4 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/tools/misc/xen-ctx.c b/tools/misc/xen-ctx.c
index c31dd5d8e9..8f9692843b 100644
--- a/tools/misc/xen-ctx.c
+++ b/tools/misc/xen-ctx.c
@@ -57,6 +57,13 @@ static void dump_header(void)
            h.magic, h.version);
 }
 
+static void dump_shared_info(void)
+{
+    DOMAIN_SAVE_TYPE(SHARED_INFO) s;
+    READ(s);
+    printf("    SHARED_INFO: field_width %u\n", s.field_width);
+}
+
 static void dump_end(void)
 {
     DOMAIN_SAVE_TYPE(END) e;
@@ -124,6 +131,7 @@ int main(int argc, char **argv)
         switch (desc.typecode)
         {
         case DOMAIN_SAVE_CODE(HEADER): dump_header(); break;
+        case DOMAIN_SAVE_CODE(SHARED_INFO): dump_shared_info(); break;
         case DOMAIN_SAVE_CODE(END): dump_end(); return 0;
         default:
             printf("Unknown type %u: skipping\n", desc.typecode);
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 3dcd73f67c..484f6bde13 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -33,6 +33,7 @@
 #include <xen/xenoprof.h>
 #include <xen/irq.h>
 #include <xen/argo.h>
+#include <xen/save.h>
 #include <asm/debugger.h>
 #include <asm/p2m.h>
 #include <asm/processor.h>
@@ -1646,6 +1647,60 @@ int continue_hypercall_on_cpu(
     return 0;
 }
 
+static int save_shared_info(const struct vcpu *v, struct domain_context *c,
+                            bool dry_run)
+{
+    struct domain *d = v->domain;
+    struct domain_shared_info_context ctxt = {};
+
+    if ( !dry_run )
+    {
+        memcpy(ctxt.buffer, d->shared_info, PAGE_SIZE);
+        ctxt.field_width = has_32bit_shinfo(d) ? 4 : 8;
+    }
+
+    return DOMAIN_SAVE_ENTRY(SHARED_INFO, c, v, &ctxt, sizeof(ctxt));
+}
+
+static int load_shared_info(struct vcpu *v, struct domain_context *c)
+{
+    struct domain *d = v->domain;
+    struct domain_shared_info_context ctxt;
+    unsigned int i;
+    int rc;
+
+    rc = DOMAIN_LOAD_ENTRY(SHARED_INFO, c, v, &ctxt, sizeof(ctxt), true);
+    if ( rc )
+        return rc;
+
+    for ( i = 0; i < ARRAY_SIZE(ctxt.pad); i++ )
+        if ( ctxt.pad[i] )
+            return -EINVAL;
+
+    switch ( ctxt.field_width )
+    {
+    case 4:
+        d->arch.has_32bit_shinfo = 1;
+        break;
+
+    case 8:
+        d->arch.has_32bit_shinfo = 0;
+        break;
+
+    default:
+        rc = -EINVAL;
+        break;
+    }
+
+    if ( !rc )
+        memcpy(d->shared_info, ctxt.buffer, PAGE_SIZE);
+
+    return rc;
+}
+
+DOMAIN_REGISTER_SAVE_RESTORE(SHARED_INFO, false, save_shared_info,
+                             load_shared_info);
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/public/save.h b/xen/include/public/save.h
index 84981cd0f6..ff804a7dbf 100644
--- a/xen/include/public/save.h
+++ b/xen/include/public/save.h
@@ -69,6 +69,14 @@ struct domain_save_header {
 };
 DECLARE_DOMAIN_SAVE_TYPE(HEADER, 1, struct domain_save_header);
 
-#define DOMAIN_SAVE_CODE_MAX 1
+struct domain_shared_info_context {
+    uint8_t buffer[XEN_PAGE_SIZE];
+    uint8_t field_width;
+    uint8_t pad[7];
+};
+
+DECLARE_DOMAIN_SAVE_TYPE(SHARED_INFO, 2, struct domain_shared_info_context);
+
+#define DOMAIN_SAVE_CODE_MAX 2
 
 #endif /* __XEN_PUBLIC_SAVE_H__ */
diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index 75b1619d0d..cbf603f289 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -37,6 +37,9 @@
 #error "Unsupported architecture"
 #endif
 
+/* The Xen ABI assumes a page size of 4k. */
+#define XEN_PAGE_SIZE 4096
+
 #ifndef __ASSEMBLY__
 /* Guest handles for primitive C types. */
 DEFINE_XEN_GUEST_HANDLE(char);
-- 
2.20.1