[Xen-changelog] [xen staging] x86/microcode: refuse to load the same revision ucode

[patchbot@xxxxxxx]

commit 72580a8d3c7ac70859437b69570de67dab668d9f
Author:     Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
AuthorDate: Wed Nov 27 10:04:30 2019 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Nov 27 12:53:41 2019 +0000

    x86/microcode: refuse to load the same revision ucode
    
    Currently if a user tries to live-load the same or older ucode revision
    than CPU already has, he will get a single message in Xen log like:
    
        (XEN) 128 cores are to update their microcode
    
    No actual ucode loading will happen and this situation can be quite
    confusing. Fix this by starting ucode update only when the provided
    ucode revision is higher than the currently cached one (if any).
    This is based on the property that if microcode_cache exists, all CPUs
    in the system should have at least that ucode revision.
    
    Additionally, print a user friendly message if no matching or newer
    ucode can be found in the provided blob. This also requires ignoring
    -ENODATA in AMD-side code, otherwise the message given to the user is:
    
        (XEN) Parsing microcode blob error -61
    
    Which actually means that a ucode blob was parsed fine, but no matching
    ucode was found.
    
    Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
    Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/microcode.c     | 20 ++++++++++++++++++++
 xen/arch/x86/microcode_amd.c |  7 +++++++
 2 files changed, 27 insertions(+)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 65d1f41e7c..6ced293d88 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -640,10 +640,30 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) 
buf, unsigned long len)
 
     if ( !patch )
     {
+        printk(XENLOG_WARNING "microcode: couldn't find any matching ucode in "
+                              "the provided blob!\n");
         ret = -ENOENT;
         goto put;
     }
 
+    /*
+     * If microcode_cache exists, all CPUs in the system should have at least
+     * that ucode revision.
+     */
+    spin_lock(&microcode_mutex);
+    if ( microcode_cache &&
+         microcode_ops->compare_patch(patch, microcode_cache) != NEW_UCODE )
+    {
+        spin_unlock(&microcode_mutex);
+        printk(XENLOG_WARNING "microcode: couldn't find any newer revision "
+                              "in the provided blob!\n");
+        microcode_free_patch(patch);
+        ret = -ENOENT;
+
+        goto put;
+    }
+    spin_unlock(&microcode_mutex);
+
     if ( microcode_ops->start_update )
     {
         ret = microcode_ops->start_update();
diff --git a/xen/arch/x86/microcode_amd.c b/xen/arch/x86/microcode_amd.c
index 1e52f7f49a..00750f7bbb 100644
--- a/xen/arch/x86/microcode_amd.c
+++ b/xen/arch/x86/microcode_amd.c
@@ -502,6 +502,13 @@ static struct microcode_patch *cpu_request_microcode(const 
void *buf,
 
     if ( error )
     {
+        /*
+         * -ENODATA here means that the blob was parsed fine but no matching
+         * ucode was found. Don't return it to the caller.
+         */
+        if ( error == -ENODATA )
+            error = 0;
+
         xfree(mc_amd->equiv_cpu_table);
         xfree(mc_amd);
         goto out;
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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