[Xen-devel] [PATCH v1 for 4.13] x86/microcode: refuse to load the same revision ucode

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

Currently if a user tries to live-load the same ucode revision that 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 a newer ucode
revision has been provided. This is based on an assumption that all CPUs
in the system have the same ucode revision. If that's not the case,
the system must be considered unstable.

Additionally, print a user friendly message if no newer ucode can be
found. This also requires ignoring -ENODATA in AMD-side code, otherwise
the message given to 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>
---
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Chao Gao <chao.gao@xxxxxxxxx>
CC: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/microcode.c       | 2 ++
 xen/arch/x86/microcode_amd.c   | 4 ++--
 xen/arch/x86/microcode_intel.c | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
index 65d1f41e7c..255613569d 100644
--- a/xen/arch/x86/microcode.c
+++ b/xen/arch/x86/microcode.c
@@ -641,6 +641,8 @@ int microcode_update(XEN_GUEST_HANDLE_PARAM(const_void) 
buf, unsigned long len)
     if ( !patch )
     {
         ret = -ENOENT;
+        printk(XENLOG_WARNING "microcode: couldn't find any newer revision in "
+                              "the provided blob!\n");
         goto put;
     }
 
diff --git a/xen/arch/x86/microcode_amd.c b/xen/arch/x86/microcode_amd.c
index 1e52f7f49a..dd81b5239a 100644
--- a/xen/arch/x86/microcode_amd.c
+++ b/xen/arch/x86/microcode_amd.c
@@ -518,7 +518,7 @@ static struct microcode_patch *cpu_request_microcode(const 
void *buf,
          * If the new ucode covers current CPU, compare ucodes and store the
          * one with higher revision.
          */
-        if ( (microcode_fits(mc_amd) != MIS_UCODE) &&
+        if ( (microcode_fits(mc_amd) == NEW_UCODE) &&
              (!saved || (compare_header(mc_amd->mpb, saved) == NEW_UCODE)) )
         {
             xfree(saved);
@@ -576,7 +576,7 @@ static struct microcode_patch *cpu_request_microcode(const 
void *buf,
         free_patch(mc_amd);
 
   out:
-    if ( error && !patch )
+    if ( error && error != -ENODATA && !patch )
         patch = ERR_PTR(error);
 
     return patch;
diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
index 9f66057aad..a76b860226 100644
--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -377,7 +377,7 @@ static struct microcode_patch *cpu_request_microcode(const 
void *buf,
          * If the new update covers current CPU, compare updates and store the
          * one with higher revision.
          */
-        if ( (microcode_update_match(&mc->hdr) != MIS_UCODE) &&
+        if ( (microcode_update_match(&mc->hdr) == NEW_UCODE) &&
              (!saved || (mc->hdr.rev > saved->hdr.rev)) )
         {
             xfree(saved);
-- 
2.17.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel