[PATCH v2] x86/microcode: Handle negative microcode revisions

[PATCH v2] x86/microcode: Handle negative microcode revisions

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

The Intel microcode revision space is unsigned. Inside Intel there are special
microcodes that have the highest bit set, and they are considered to have
a higher revision than any microcodes that don't have this bit set.

The function comparing the microcode revision in the Linux driver compares
u32 with int, which ends up being signed extended to long on 64bit
systems. This results in these highest bit set microcode revision not loading
because their revision appears negative and smaller than the
existing microcode.

Change the comparison to unsigned. With that the loading works
as expected.

Cc: stable@vger.kernel.org # Any supported stable
Signed-off-by: Andi Kleen <ak@linux.intel.com>
--
v2: White space changes.
---
 arch/x86/kernel/cpu/microcode/intel.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 16936a24795c..e54d402500d3 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -93,7 +93,8 @@ static int find_matching_signature(void *mc, unsigned int csig, int cpf)
 /*
  * Returns 1 if update has been found, 0 otherwise.
  */
-static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev)
+static int has_newer_microcode(void *mc, unsigned int csig, int cpf,
+			       unsigned new_rev)
 {
 	struct microcode_header_intel *mc_hdr = mc;
 
-- 
2.17.1

Re: [PATCH v2] x86/microcode: Handle negative microcode revisions

[Borislav Petkov]

Dropping stable.

On Sat, Oct 20, 2018 at 07:41:58AM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> 
> The Intel microcode revision space is unsigned. Inside Intel there are special
> microcodes that have the highest bit set, and they are considered to have
> a higher revision than any microcodes that don't have this bit set.
> 
> The function comparing the microcode revision in the Linux driver compares
> u32 with int, which ends up being signed extended to long on 64bit
> systems. This results in these highest bit set microcode revision not loading
> because their revision appears negative and smaller than the
> existing microcode.
> 
> Change the comparison to unsigned. With that the loading works
> as expected.
> 
> Cc: stable@vger.kernel.org # Any supported stable
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> --
> v2: White space changes.
> ---
>  arch/x86/kernel/cpu/microcode/intel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> index 16936a24795c..e54d402500d3 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -93,7 +93,8 @@ static int find_matching_signature(void *mc, unsigned int csig, int cpf)
>  /*
>   * Returns 1 if update has been found, 0 otherwise.
>   */
> -static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev)
> +static int has_newer_microcode(void *mc, unsigned int csig, int cpf,
> +			       unsigned new_rev)
>  {
>  	struct microcode_header_intel *mc_hdr = mc;
>  
> -- 

Please incorporate all review comments before sending a new version of
your patch.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH v2] x86/microcode: Handle negative microcode revisions

[Andi Kleen]

On Sat, Oct 20, 2018 at 07:41:36PM +0200, Borislav Petkov wrote:
> Dropping stable.
> 
> On Sat, Oct 20, 2018 at 07:41:58AM -0700, Andi Kleen wrote:
> > From: Andi Kleen <ak@linux.intel.com>
> > 
> > The Intel microcode revision space is unsigned. Inside Intel there are special
> > microcodes that have the highest bit set, and they are considered to have
> > a higher revision than any microcodes that don't have this bit set.
> > 
> > The function comparing the microcode revision in the Linux driver compares
> > u32 with int, which ends up being signed extended to long on 64bit
> > systems. This results in these highest bit set microcode revision not loading
> > because their revision appears negative and smaller than the
> > existing microcode.
> > 
> > Change the comparison to unsigned. With that the loading works
> > as expected.
> > 
> > Cc: stable@vger.kernel.org # Any supported stable
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> > --
> > v2: White space changes.
> > ---
> >  arch/x86/kernel/cpu/microcode/intel.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> > index 16936a24795c..e54d402500d3 100644
> > --- a/arch/x86/kernel/cpu/microcode/intel.c
> > +++ b/arch/x86/kernel/cpu/microcode/intel.c
> > @@ -93,7 +93,8 @@ static int find_matching_signature(void *mc, unsigned int csig, int cpf)
> >  /*
> >   * Returns 1 if update has been found, 0 otherwise.
> >   */
> > -static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev)
> > +static int has_newer_microcode(void *mc, unsigned int csig, int cpf,
> > +			       unsigned new_rev)
> >  {
> >  	struct microcode_header_intel *mc_hdr = mc;
> >  
> > -- 
> 
> Please incorporate all review comments before sending a new version of
> your patch.

I replaced one more microcodes with microcodes revisions if that is
what you meant.

-Andi