x86/ucode/intel: Writeback and invalidate caches before updating microcode

Commit Message

Andrew Cooper May 4, 2020, 12:47 p.m. UTC

From: Ashok Raj <[e-mail]>

Updating microcode is less error prone when caches have been flushed and
depending on what exactly the microcode is updating. For example, some of the
issues around certain Broadwell parts can be addressed by doing a full cache
flush.

Signed-off-by: Ashok Raj <[e-mail]>
Signed-off-by: Borislav Petkov <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
[Linux commit 91df9fdf51492aec9fed6b4cbd33160886740f47, ported to Xen]
Signed-off-by: Andrew Cooper <[e-mail]>
---
CC: Jan Beulich <[e-mail]>
CC: Wei Liu <[e-mail]>
CC: Roger Pau Monné <[e-mail]>
---
 xen/arch/x86/cpu/microcode/intel.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Jan Beulich May 4, 2020, 12:52 p.m. UTC | #1

On 04.05.2020 14:47, Andrew Cooper wrote:
> From: Ashok Raj <[e-mail]>
> 
> Updating microcode is less error prone when caches have been flushed and
> depending on what exactly the microcode is updating. For example, some of the
> issues around certain Broadwell parts can be addressed by doing a full cache
> flush.
> 
> Signed-off-by: Ashok Raj <[e-mail]>
> Signed-off-by: Borislav Petkov <[e-mail]>
> Signed-off-by: Thomas Gleixner <[e-mail]>
> [Linux commit 91df9fdf51492aec9fed6b4cbd33160886740f47, ported to Xen]
> Signed-off-by: Andrew Cooper <[e-mail]>

Acked-by: Jan Beulich <[e-mail]>

Patch

diff --git a/xen/arch/x86/cpu/microcode/intel.c b/xen/arch/x86/cpu/microcode/intel.c
index a9f4d6e829..d031196d4c 100644
--- a/xen/arch/x86/cpu/microcode/intel.c
+++ b/xen/arch/x86/cpu/microcode/intel.c
@@ -25,6 +25,7 @@ 
 #include <xen/init.h>
 
 #include <asm/msr.h>
+#include <asm/system.h>
 
 #include "private.h"
 
@@ -267,6 +268,8 @@  static int apply_microcode(const struct microcode_patch *patch)
     if ( microcode_update_match(patch) != NEW_UCODE )
         return -EINVAL;
 
+    wbinvd();
+
     /* write microcode via MSR 0x79 */
     wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)patch->data);
     wrmsrl(MSR_IA32_UCODE_REV, 0x0ULL);