[PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Suchit Karunakaran]

Fix a logic bug in early_init_intel() where a conditional range check:
(c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
was always false due to (PRESCOTT) being numerically greater than the
upper bound (WILLAMETTE). This triggers:-Werror=logical-op: 
logical ‘and’ of mutually exclusive tests is always false
The fix corrects the constant ordering to ensure the range is valid:
(c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)

Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
constant_tsc model checks")

Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>

Changes since v1:
- Fix incorrect logic
---
 arch/x86/kernel/cpu/intel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 076eaa41b8c8..6f5bd5dbc249 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
 	if (c->x86_power & (1 << 8)) {
 		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
 		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
-	} else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
+	} else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
 		   (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
 		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
 	}
-- 
2.50.1

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Greg KH]

On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran wrote:
> Fix a logic bug in early_init_intel() where a conditional range check:
> (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> was always false due to (PRESCOTT) being numerically greater than the
> upper bound (WILLAMETTE). This triggers:-Werror=logical-op: 
> logical ‘and’ of mutually exclusive tests is always false
> The fix corrects the constant ordering to ensure the range is valid:
> (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> 
> Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> constant_tsc model checks")
> 
> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> 
> Changes since v1:
> - Fix incorrect logic
> ---
>  arch/x86/kernel/cpu/intel.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index 076eaa41b8c8..6f5bd5dbc249 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
>  	if (c->x86_power & (1 << 8)) {
>  		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>  		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> -	} else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> +	} else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
>  		   (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
>  		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>  	}
> -- 
> 2.50.1
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You have marked a patch with a "Fixes:" tag for a commit that is in an
  older released kernel, yet you do not have a cc: stable line in the
  signed-off-by area at all, which means that the patch will not be
  applied to any older kernel releases.  To properly fix this, please
  follow the documented rules in the
  Documentation/process/stable-kernel-rules.rst file for how to resolve
  this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Suchit Karunakaran]

On Tue, 29 Jul 2025 at 10:58, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran wrote:
> > Fix a logic bug in early_init_intel() where a conditional range check:
> > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> > was always false due to (PRESCOTT) being numerically greater than the
> > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
> > logical ‘and’ of mutually exclusive tests is always false
> > The fix corrects the constant ordering to ensure the range is valid:
> > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> >
> > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> > constant_tsc model checks")
> >
> > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> >
> > Changes since v1:
> > - Fix incorrect logic
> > ---
> >  arch/x86/kernel/cpu/intel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > index 076eaa41b8c8..6f5bd5dbc249 100644
> > --- a/arch/x86/kernel/cpu/intel.c
> > +++ b/arch/x86/kernel/cpu/intel.c
> > @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> >       if (c->x86_power & (1 << 8)) {
> >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
> >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
> >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> >       }
> > --
> > 2.50.1
> >
> >
>
> Hi,
>
> This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
> a patch that has triggered this response.  He used to manually respond
> to these common problems, but in order to save his sanity (he kept
> writing the same thing over and over, yet to different people), I was
> created.  Hopefully you will not take offence and will fix the problem
> in your patch and resubmit it so that it can be accepted into the Linux
> kernel tree.
>
> You are receiving this message because of the following common error(s)
> as indicated below:
>
> - You have marked a patch with a "Fixes:" tag for a commit that is in an
>   older released kernel, yet you do not have a cc: stable line in the
>   signed-off-by area at all, which means that the patch will not be
>   applied to any older kernel releases.  To properly fix this, please
>   follow the documented rules in the
>   Documentation/process/stable-kernel-rules.rst file for how to resolve
>   this.
>
> If you wish to discuss this problem further, or you have questions about
> how to resolve this issue, please feel free to respond to this email and
> Greg will reply once he has dug out from the pending patches received
> from other developers.
>
> thanks,
>
> greg k-h's patch email bot

Hi Greg,
I've a question regarding backporting this fix. Can this fix be
backported to stable kernel version 6.15.8? Also, should I send the
backport patch only after the initial patch has been merged in
mainline or linux-next?

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Greg KH]

On Tue, Jul 29, 2025 at 12:23:27PM +0530, Suchit Karunakaran wrote:
> On Tue, 29 Jul 2025 at 10:58, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran wrote:
> > > Fix a logic bug in early_init_intel() where a conditional range check:
> > > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> > > was always false due to (PRESCOTT) being numerically greater than the
> > > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
> > > logical ‘and’ of mutually exclusive tests is always false
> > > The fix corrects the constant ordering to ensure the range is valid:
> > > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> > >
> > > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> > > constant_tsc model checks")
> > >
> > > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> > >
> > > Changes since v1:
> > > - Fix incorrect logic
> > > ---
> > >  arch/x86/kernel/cpu/intel.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > > index 076eaa41b8c8..6f5bd5dbc249 100644
> > > --- a/arch/x86/kernel/cpu/intel.c
> > > +++ b/arch/x86/kernel/cpu/intel.c
> > > @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> > >       if (c->x86_power & (1 << 8)) {
> > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> > > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> > > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
> > >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
> > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > >       }
> > > --
> > > 2.50.1
> > >
> > >
> >
> > Hi,
> >
> > This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
> > a patch that has triggered this response.  He used to manually respond
> > to these common problems, but in order to save his sanity (he kept
> > writing the same thing over and over, yet to different people), I was
> > created.  Hopefully you will not take offence and will fix the problem
> > in your patch and resubmit it so that it can be accepted into the Linux
> > kernel tree.
> >
> > You are receiving this message because of the following common error(s)
> > as indicated below:
> >
> > - You have marked a patch with a "Fixes:" tag for a commit that is in an
> >   older released kernel, yet you do not have a cc: stable line in the
> >   signed-off-by area at all, which means that the patch will not be
> >   applied to any older kernel releases.  To properly fix this, please
> >   follow the documented rules in the
> >   Documentation/process/stable-kernel-rules.rst file for how to resolve
> >   this.
> >
> > If you wish to discuss this problem further, or you have questions about
> > how to resolve this issue, please feel free to respond to this email and
> > Greg will reply once he has dug out from the pending patches received
> > from other developers.
> >
> > thanks,
> >
> > greg k-h's patch email bot
> 
> Hi Greg,
> I've a question regarding backporting this fix. Can this fix be
> backported to stable kernel version 6.15.8? Also, should I send the
> backport patch only after the initial patch has been merged in
> mainline or linux-next?

Did you read the document that my bot linked to above?  It should answer
those questions :)

thanks,

greg k-h

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Suchit Karunakaran]

On Tue, 29 Jul 2025 at 13:26, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jul 29, 2025 at 12:23:27PM +0530, Suchit Karunakaran wrote:
> > On Tue, 29 Jul 2025 at 10:58, Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran wrote:
> > > > Fix a logic bug in early_init_intel() where a conditional range check:
> > > > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> > > > was always false due to (PRESCOTT) being numerically greater than the
> > > > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
> > > > logical ‘and’ of mutually exclusive tests is always false
> > > > The fix corrects the constant ordering to ensure the range is valid:
> > > > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> > > >
> > > > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> > > > constant_tsc model checks")
> > > >
> > > > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> > > >
> > > > Changes since v1:
> > > > - Fix incorrect logic
> > > > ---
> > > >  arch/x86/kernel/cpu/intel.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > > > index 076eaa41b8c8..6f5bd5dbc249 100644
> > > > --- a/arch/x86/kernel/cpu/intel.c
> > > > +++ b/arch/x86/kernel/cpu/intel.c
> > > > @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> > > >       if (c->x86_power & (1 << 8)) {
> > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > > >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> > > > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> > > > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
> > > >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
> > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > > >       }
> > > > --
> > > > 2.50.1
> > > >
> > > >
> > >
> > > Hi,
> > >
> > > This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
> > > a patch that has triggered this response.  He used to manually respond
> > > to these common problems, but in order to save his sanity (he kept
> > > writing the same thing over and over, yet to different people), I was
> > > created.  Hopefully you will not take offence and will fix the problem
> > > in your patch and resubmit it so that it can be accepted into the Linux
> > > kernel tree.
> > >
> > > You are receiving this message because of the following common error(s)
> > > as indicated below:
> > >
> > > - You have marked a patch with a "Fixes:" tag for a commit that is in an
> > >   older released kernel, yet you do not have a cc: stable line in the
> > >   signed-off-by area at all, which means that the patch will not be
> > >   applied to any older kernel releases.  To properly fix this, please
> > >   follow the documented rules in the
> > >   Documentation/process/stable-kernel-rules.rst file for how to resolve
> > >   this.
> > >
> > > If you wish to discuss this problem further, or you have questions about
> > > how to resolve this issue, please feel free to respond to this email and
> > > Greg will reply once he has dug out from the pending patches received
> > > from other developers.
> > >
> > > thanks,
> > >
> > > greg k-h's patch email bot
> >
> > Hi Greg,
> > I've a question regarding backporting this fix. Can this fix be
> > backported to stable kernel version 6.15.8? Also, should I send the
> > backport patch only after the initial patch has been merged in
> > mainline or linux-next?
>
> Did you read the document that my bot linked to above?  It should answer
> those questions :)
>
> thanks,
>
> greg k-h

Hi Greg,
I did go through the document you linked. I just wanted to clarify
about the backporting process, especially since the merge window has
already started and it might take some time for this to be merged into
mainline. Regardless, I'll send the backport patch after the initial
one has been merged.
Thanks again, and I apologize for any inconvenience.

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Greg KH]

On Tue, Jul 29, 2025 at 02:24:43PM +0530, Suchit Karunakaran wrote:
> On Tue, 29 Jul 2025 at 13:26, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Tue, Jul 29, 2025 at 12:23:27PM +0530, Suchit Karunakaran wrote:
> > > On Tue, 29 Jul 2025 at 10:58, Greg KH <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran wrote:
> > > > > Fix a logic bug in early_init_intel() where a conditional range check:
> > > > > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> > > > > was always false due to (PRESCOTT) being numerically greater than the
> > > > > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
> > > > > logical ‘and’ of mutually exclusive tests is always false
> > > > > The fix corrects the constant ordering to ensure the range is valid:
> > > > > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> > > > >
> > > > > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> > > > > constant_tsc model checks")
> > > > >
> > > > > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> > > > >
> > > > > Changes since v1:
> > > > > - Fix incorrect logic
> > > > > ---
> > > > >  arch/x86/kernel/cpu/intel.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > > > > index 076eaa41b8c8..6f5bd5dbc249 100644
> > > > > --- a/arch/x86/kernel/cpu/intel.c
> > > > > +++ b/arch/x86/kernel/cpu/intel.c
> > > > > @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> > > > >       if (c->x86_power & (1 << 8)) {
> > > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > > > >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> > > > > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> > > > > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
> > > > >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
> > > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > > > >       }
> > > > > --
> > > > > 2.50.1
> > > > >
> > > > >
> > > >
> > > > Hi,
> > > >
> > > > This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
> > > > a patch that has triggered this response.  He used to manually respond
> > > > to these common problems, but in order to save his sanity (he kept
> > > > writing the same thing over and over, yet to different people), I was
> > > > created.  Hopefully you will not take offence and will fix the problem
> > > > in your patch and resubmit it so that it can be accepted into the Linux
> > > > kernel tree.
> > > >
> > > > You are receiving this message because of the following common error(s)
> > > > as indicated below:
> > > >
> > > > - You have marked a patch with a "Fixes:" tag for a commit that is in an
> > > >   older released kernel, yet you do not have a cc: stable line in the
> > > >   signed-off-by area at all, which means that the patch will not be
> > > >   applied to any older kernel releases.  To properly fix this, please
> > > >   follow the documented rules in the
> > > >   Documentation/process/stable-kernel-rules.rst file for how to resolve
> > > >   this.
> > > >
> > > > If you wish to discuss this problem further, or you have questions about
> > > > how to resolve this issue, please feel free to respond to this email and
> > > > Greg will reply once he has dug out from the pending patches received
> > > > from other developers.
> > > >
> > > > thanks,
> > > >
> > > > greg k-h's patch email bot
> > >
> > > Hi Greg,
> > > I've a question regarding backporting this fix. Can this fix be
> > > backported to stable kernel version 6.15.8? Also, should I send the
> > > backport patch only after the initial patch has been merged in
> > > mainline or linux-next?
> >
> > Did you read the document that my bot linked to above?  It should answer
> > those questions :)
> >
> > thanks,
> >
> > greg k-h
> 
> Hi Greg,
> I did go through the document you linked. I just wanted to clarify
> about the backporting process, especially since the merge window has
> already started and it might take some time for this to be merged into
> mainline. Regardless, I'll send the backport patch after the initial
> one has been merged.

As the document states, a commit must be in Linus's tree first, before
we can consider it for any stable release.

thanks,

greg k-h

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Suchit Karunakaran]

On Tue, 29 Jul 2025 at 14:31, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jul 29, 2025 at 02:24:43PM +0530, Suchit Karunakaran wrote:
> > On Tue, 29 Jul 2025 at 13:26, Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Tue, Jul 29, 2025 at 12:23:27PM +0530, Suchit Karunakaran wrote:
> > > > On Tue, 29 Jul 2025 at 10:58, Greg KH <gregkh@linuxfoundation.org> wrote:
> > > > >
> > > > > On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran wrote:
> > > > > > Fix a logic bug in early_init_intel() where a conditional range check:
> > > > > > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> > > > > > was always false due to (PRESCOTT) being numerically greater than the
> > > > > > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
> > > > > > logical ‘and’ of mutually exclusive tests is always false
> > > > > > The fix corrects the constant ordering to ensure the range is valid:
> > > > > > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> > > > > >
> > > > > > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> > > > > > constant_tsc model checks")
> > > > > >
> > > > > > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> > > > > >
> > > > > > Changes since v1:
> > > > > > - Fix incorrect logic
> > > > > > ---
> > > > > >  arch/x86/kernel/cpu/intel.c | 2 +-
> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > > > > > index 076eaa41b8c8..6f5bd5dbc249 100644
> > > > > > --- a/arch/x86/kernel/cpu/intel.c
> > > > > > +++ b/arch/x86/kernel/cpu/intel.c
> > > > > > @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> > > > > >       if (c->x86_power & (1 << 8)) {
> > > > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > > > > >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> > > > > > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> > > > > > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
> > > > > >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
> > > > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > > > > >       }
> > > > > > --
> > > > > > 2.50.1
> > > > > >
> > > > > >
> > > > >
> > > > > Hi,
> > > > >
> > > > > This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
> > > > > a patch that has triggered this response.  He used to manually respond
> > > > > to these common problems, but in order to save his sanity (he kept
> > > > > writing the same thing over and over, yet to different people), I was
> > > > > created.  Hopefully you will not take offence and will fix the problem
> > > > > in your patch and resubmit it so that it can be accepted into the Linux
> > > > > kernel tree.
> > > > >
> > > > > You are receiving this message because of the following common error(s)
> > > > > as indicated below:
> > > > >
> > > > > - You have marked a patch with a "Fixes:" tag for a commit that is in an
> > > > >   older released kernel, yet you do not have a cc: stable line in the
> > > > >   signed-off-by area at all, which means that the patch will not be
> > > > >   applied to any older kernel releases.  To properly fix this, please
> > > > >   follow the documented rules in the
> > > > >   Documentation/process/stable-kernel-rules.rst file for how to resolve
> > > > >   this.
> > > > >
> > > > > If you wish to discuss this problem further, or you have questions about
> > > > > how to resolve this issue, please feel free to respond to this email and
> > > > > Greg will reply once he has dug out from the pending patches received
> > > > > from other developers.
> > > > >
> > > > > thanks,
> > > > >
> > > > > greg k-h's patch email bot
> > > >
> > > > Hi Greg,
> > > > I've a question regarding backporting this fix. Can this fix be
> > > > backported to stable kernel version 6.15.8? Also, should I send the
> > > > backport patch only after the initial patch has been merged in
> > > > mainline or linux-next?
> > >
> > > Did you read the document that my bot linked to above?  It should answer
> > > those questions :)
> > >
> > > thanks,
> > >
> > > greg k-h
> >
> > Hi Greg,
> > I did go through the document you linked. I just wanted to clarify
> > about the backporting process, especially since the merge window has
> > already started and it might take some time for this to be merged into
> > mainline. Regardless, I'll send the backport patch after the initial
> > one has been merged.
>
> As the document states, a commit must be in Linus's tree first, before
> we can consider it for any stable release.
>
> thanks,
>
> greg k-h

Hi Greg,
Thank you for the clarification. I now understand that a commit must
be in Linus's tree before it can be considered for any stable release.
I apologize for the repeated questions and any inconvenience.

Thanks,
Suchit

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Sohil Mehta]

Though the title is correct, it is better to make it more precise.
Something like:

x86/cpu/intel: Fix the constant_tsc model check for Pentium 4s

On 7/28/2025 9:26 PM, Suchit Karunakaran wrote:
> Fix a logic bug in early_init_intel() where a conditional range check:
> (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> was always false due to (PRESCOTT) being numerically greater than the
> upper bound (WILLAMETTE). This triggers:-Werror=logical-op: 
> logical ‘and’ of mutually exclusive tests is always false

We can focus on the why instead of how this error was found. How about
wording it as below?

The logic to synthesize constant_tsc for Pentium 4s (Family 15) is
wrong. Since INTEL_P4_PRESCOTT is numerically greater than
INTEL_P4_WILLAMETTE, the logic always results in false and never sets
X86_FEATURE_CONSTANT_TSC for any Pentium 4 model.

The error was introduced while replacing the x86_model check with a VFM
one. The original check was as follows:

	if ((c->x86 == 0xf && c->x86_model >= 0x03) ||
		(c->x86 == 0x6 && c->x86_model >= 0x0e))
		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);

Fix the logic to cover all Pentium 4 models from Prescott (model 3) to
Cedarmill (model 6) which is the last model released in Family 15.

> The fix corrects the constant ordering to ensure the range is valid:
> (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> 

This line is unnecessary. Changes that are easily observable in the diff
below don't need to be described in the commit message.

> Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> constant_tsc model checks")
> 

The "Fixes:" line doesn't need to be broken down into multiple lines.
All of it can be on the same line.

For patches being reviewed for upstream, adding a stable Cc (Option 1 in
the stable documentation) is the easiest and preferred way to
automatically trigger submissions for stable.

In this case, include the below Cc: line after the Fixes: line.

Cc: <stable@vger.kernel.org> # v6.15

> Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> 
> Changes since v1:
> - Fix incorrect logic

Patch-to-patch changes should be below the --- line. That way they will
get ignored when the patch is applied to the maintainer's tree.

> ---
>  arch/x86/kernel/cpu/intel.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index 076eaa41b8c8..6f5bd5dbc249 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
>  	if (c->x86_power & (1 << 8)) {
>  		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>  		set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> -	} else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> +	} else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
>  		   (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
>  		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>  	}

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[H. Peter Anvin]

On July 29, 2025 2:08:47 AM PDT, Suchit Karunakaran <suchitkarunakaran@gmail.com> wrote:
>On Tue, 29 Jul 2025 at 14:31, Greg KH <gregkh@linuxfoundation.org> wrote:
>>
>> On Tue, Jul 29, 2025 at 02:24:43PM +0530, Suchit Karunakaran wrote:
>> > On Tue, 29 Jul 2025 at 13:26, Greg KH <gregkh@linuxfoundation.org>
>wrote:
>> > >
>> > > On Tue, Jul 29, 2025 at 12:23:27PM +0530, Suchit Karunakaran wrote:
>> > > > On Tue, 29 Jul 2025 at 10:58, Greg KH <gregkh@linuxfoundation.org>
>wrote:
>> > > > >
>> > > > > On Tue, Jul 29, 2025 at 09:56:21AM +0530, Suchit Karunakaran
>wrote:
>> > > > > > Fix a logic bug in early_init_intel() where a conditional range
>check:
>> > > > > > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <=
>INTEL_P4_WILLAMETTE)
>> > > > > > was always false due to (PRESCOTT) being numerically greater
>than the
>> > > > > > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
>> > > > > > logical ‘and’ of mutually exclusive tests is always false
>> > > > > > The fix corrects the constant ordering to ensure the range is
>valid:
>> > > > > > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <=
>INTEL_P4_CEDARMILL)
>> > > > > >
>> > > > > > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
>> > > > > > constant_tsc model checks")
>> > > > > >
>> > > > > > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
>> > > > > >
>> > > > > > Changes since v1:
>> > > > > > - Fix incorrect logic
>> > > > > > ---
>> > > > > >  arch/x86/kernel/cpu/intel.c | 2 +-
>> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
>> > > > > >
>> > > > > > diff --git a/arch/x86/kernel/cpu/intel.c
>b/arch/x86/kernel/cpu/intel.c
>> > > > > > index 076eaa41b8c8..6f5bd5dbc249 100644
>> > > > > > --- a/arch/x86/kernel/cpu/intel.c
>> > > > > > +++ b/arch/x86/kernel/cpu/intel.c
>> > > > > > @@ -262,7 +262,7 @@ static void early_init_intel(struct
>cpuinfo_x86 *c)
>> > > > > >       if (c->x86_power & (1 << 8)) {
>> > > > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>> > > > > >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
>> > > > > > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm
><= INTEL_P4_WILLAMETTE) ||
>> > > > > > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT &&
>c->x86_vfm <= INTEL_P4_CEDARMILL) ||
>> > > > > >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm
><= INTEL_IVYBRIDGE)) {
>> > > > > >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>> > > > > >       }
>> > > > > > --
>> > > > > > 2.50.1
>> > > > > >
>> > > > > >
>> > > > >
>> > > > > Hi,
>> > > > >
>> > > > > This is the friendly patch-bot of Greg Kroah-Hartman.  You have
>sent him
>> > > > > a patch that has triggered this response.  He used to manually
>respond
>> > > > > to these common problems, but in order to save his sanity (he kept
>> > > > > writing the same thing over and over, yet to different people), I
>was
>> > > > > created.  Hopefully you will not take offence and will fix the
>problem
>> > > > > in your patch and resubmit it so that it can be accepted into the
>Linux
>> > > > > kernel tree.
>> > > > >
>> > > > > You are receiving this message because of the following common
>error(s)
>> > > > > as indicated below:
>> > > > >
>> > > > > - You have marked a patch with a "Fixes:" tag for a commit that
>is in an
>> > > > >   older released kernel, yet you do not have a cc: stable line in
>the
>> > > > >   signed-off-by area at all, which means that the patch will not
>be
>> > > > >   applied to any older kernel releases.  To properly fix this,
>please
>> > > > >   follow the documented rules in the
>> > > > >   Documentation/process/stable-kernel-rules.rst file for how to
>resolve
>> > > > >   this.
>> > > > >
>> > > > > If you wish to discuss this problem further, or you have
>questions about
>> > > > > how to resolve this issue, please feel free to respond to this
>email and
>> > > > > Greg will reply once he has dug out from the pending patches
>received
>> > > > > from other developers.
>> > > > >
>> > > > > thanks,
>> > > > >
>> > > > > greg k-h's patch email bot
>> > > >
>> > > > Hi Greg,
>> > > > I've a question regarding backporting this fix. Can this fix be
>> > > > backported to stable kernel version 6.15.8? Also, should I send the
>> > > > backport patch only after the initial patch has been merged in
>> > > > mainline or linux-next?
>> > >
>> > > Did you read the document that my bot linked to above?  It should
>answer
>> > > those questions :)
>> > >
>> > > thanks,
>> > >
>> > > greg k-h
>> >
>> > Hi Greg,
>> > I did go through the document you linked. I just wanted to clarify
>> > about the backporting process, especially since the merge window has
>> > already started and it might take some time for this to be merged into
>> > mainline. Regardless, I'll send the backport patch after the initial
>> > one has been merged.
>>
>> As the document states, a commit must be in Linus's tree first, before
>> we can consider it for any stable release.
>>
>
>Hi Greg,
>Thanks for clarifying. I understand now that a commit must be in Linus's
>tree before it can be considered for any stable release.
>I apologize for the repeated questions and any inconvenience.
>
>Thanks,
>Suchit

It does, *unless* there is a detailed explanation why it is not applicable to mainline (for example, "the code in mainline was completely rewritten and does not have the bug because...")

Re: [PATCH v2] x86/intel: Fix always false range check in x86_vfm model matching

[Suchit Karunakaran]

On Wed, 30 Jul 2025 at 00:20, Sohil Mehta <sohil.mehta@intel.com> wrote:
>
> Though the title is correct, it is better to make it more precise.
> Something like:
>
> x86/cpu/intel: Fix the constant_tsc model check for Pentium 4s
>
> On 7/28/2025 9:26 PM, Suchit Karunakaran wrote:
> > Fix a logic bug in early_init_intel() where a conditional range check:
> > (c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE)
> > was always false due to (PRESCOTT) being numerically greater than the
> > upper bound (WILLAMETTE). This triggers:-Werror=logical-op:
> > logical ‘and’ of mutually exclusive tests is always false
>
> We can focus on the why instead of how this error was found. How about
> wording it as below?
>
> The logic to synthesize constant_tsc for Pentium 4s (Family 15) is
> wrong. Since INTEL_P4_PRESCOTT is numerically greater than
> INTEL_P4_WILLAMETTE, the logic always results in false and never sets
> X86_FEATURE_CONSTANT_TSC for any Pentium 4 model.
>
> The error was introduced while replacing the x86_model check with a VFM
> one. The original check was as follows:
>
>         if ((c->x86 == 0xf && c->x86_model >= 0x03) ||
>                 (c->x86 == 0x6 && c->x86_model >= 0x0e))
>                 set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
>
> Fix the logic to cover all Pentium 4 models from Prescott (model 3) to
> Cedarmill (model 6) which is the last model released in Family 15.
>
> > The fix corrects the constant ordering to ensure the range is valid:
> > (c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL)
> >
>
> This line is unnecessary. Changes that are easily observable in the diff
> below don't need to be described in the commit message.
>
> > Fixes: fadb6f569b10 ("x86/cpu/intel: Limit the non-architectural
> > constant_tsc model checks")
> >
>
> The "Fixes:" line doesn't need to be broken down into multiple lines.
> All of it can be on the same line.
>
> For patches being reviewed for upstream, adding a stable Cc (Option 1 in
> the stable documentation) is the easiest and preferred way to
> automatically trigger submissions for stable.
>
> In this case, include the below Cc: line after the Fixes: line.
>
> Cc: <stable@vger.kernel.org> # v6.15
>
> > Signed-off-by: Suchit Karunakaran <suchitkarunakaran@gmail.com>
> >
> > Changes since v1:
> > - Fix incorrect logic
>
> Patch-to-patch changes should be below the --- line. That way they will
> get ignored when the patch is applied to the maintainer's tree.
>
> > ---
> >  arch/x86/kernel/cpu/intel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > index 076eaa41b8c8..6f5bd5dbc249 100644
> > --- a/arch/x86/kernel/cpu/intel.c
> > +++ b/arch/x86/kernel/cpu/intel.c
> > @@ -262,7 +262,7 @@ static void early_init_intel(struct cpuinfo_x86 *c)
> >       if (c->x86_power & (1 << 8)) {
> >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> >               set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
> > -     } else if ((c->x86_vfm >= INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_WILLAMETTE) ||
> > +     } else if ((c->x86_vfm >=  INTEL_P4_PRESCOTT && c->x86_vfm <= INTEL_P4_CEDARMILL) ||
> >                  (c->x86_vfm >= INTEL_CORE_YONAH  && c->x86_vfm <= INTEL_IVYBRIDGE)) {
> >               set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> >       }
>

Hi Sohil,
Thank you very much for your valuable feedback. I have incorporated
all the suggested changes and sent out the v3 patch. Could you please
review it?

Thanks,
Suchit