Re: [Xen-devel] [PATCH v3 for 4.13] x86/microcode: refuse to load the same revision ucode

[Chao Gao <chao.gao@xxxxxxxxx>]

On Tue, Nov 26, 2019 at 03:41:53PM +0000, Sergey Dyasli wrote:
>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>
>---
>v2 --> v3:
>- move ucode comparison to generic code
>- ignore -ENODATA in a different code section
>
>v1 --> v2:
>- compare provided ucode with the currently cached one
>
>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     | 19 +++++++++++++++++++
> xen/arch/x86/microcode_amd.c |  7 +++++++
> 2 files changed, 26 insertions(+)
>
>diff --git a/xen/arch/x86/microcode.c b/xen/arch/x86/microcode.c
>index 65d1f41e7c..44efc2d9b3 100644
>--- a/xen/arch/x86/microcode.c
>+++ b/xen/arch/x86/microcode.c
>@@ -640,10 +640,29 @@ 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");

The patch needs to be freed.

With it fixed,
Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>

Thanks
Chao

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