| Message ID | 20250217160844.3164003-1-ross.lagerwall@citrix.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | x86/ucode: Add option to scan microcode by default | expand |
On 17.02.2025 17:08, Ross Lagerwall wrote: > A lot of systems automatically add microcode to the initrd so it can be > useful as a vendor policy to always scan for microcode. Add a Kconfig > option to allow setting the default behaviour. > > The default behaviour is unchanged since the new option defaults to > "no". > > Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> > --- > xen/arch/x86/Kconfig | 11 +++++++++++ > xen/arch/x86/cpu/microcode/core.c | 2 +- > 2 files changed, 12 insertions(+), 1 deletion(-) Please also update the command line doc accordingly. > --- a/xen/arch/x86/Kconfig > +++ b/xen/arch/x86/Kconfig > @@ -383,6 +383,17 @@ config ALTP2M > > If unsure, stay with defaults. > > +config UCODE_SCAN_DEFAULT > + def_bool n Just "bool" will suffice. Also can you please send patches To: the list, with maintainers Cc:-ed? Jan
On 17/02/2025 4:18 pm, Jan Beulich wrote: > On 17.02.2025 17:08, Ross Lagerwall wrote: >> A lot of systems automatically add microcode to the initrd so it can be >> useful as a vendor policy to always scan for microcode. Add a Kconfig >> option to allow setting the default behaviour. >> >> The default behaviour is unchanged since the new option defaults to >> "no". >> >> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> >> --- >> xen/arch/x86/Kconfig | 11 +++++++++++ >> xen/arch/x86/cpu/microcode/core.c | 2 +- >> 2 files changed, 12 insertions(+), 1 deletion(-) > Please also update the command line doc accordingly. I've got an open task to fix both the cmdline and sphinx docs WRT changes in 4.20. I could do this too. ~Andrew
On 17/02/2025 4:08 pm, Ross Lagerwall wrote: > A lot of systems automatically add microcode to the initrd so it can be > useful as a vendor policy to always scan for microcode. Add a Kconfig > option to allow setting the default behaviour. > > The default behaviour is unchanged since the new option defaults to > "no". > > Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> I'm pretty sure this is safe on 4.20. Prior versions of Xen need the fix to make idx/scan be mutually exclusive, which hasn't been backported yet IIRC. > --- > xen/arch/x86/Kconfig | 11 +++++++++++ > xen/arch/x86/cpu/microcode/core.c | 2 +- > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig > index 9cdd04721afa..b806d8bc3319 100644 > --- a/xen/arch/x86/Kconfig > +++ b/xen/arch/x86/Kconfig > @@ -383,6 +383,17 @@ config ALTP2M > > If unsure, stay with defaults. > > +config UCODE_SCAN_DEFAULT > + def_bool n > + prompt "Scan for microcode by default" > + help > + During boot, Xen can scan the multiboot images for a CPIO archive > + containing CPU microcode to be loaded. ", which is Linux's mechanism for early microcode loading." This is quite an important point to cover. > + > + Enabling this option will cause Xen to scan for it by default. > + > + If unsure, say N. Personally I don't like this "If unsure", because it's almost always redundant with the default. In this case, it really ought to be "set if you have a Linux dom0", which in turn begs the question as to whether it ought to be bool y. ~Andrew
On Mon, Feb 17, 2025 at 4:44 PM Andrew Cooper <andrew.cooper3@citrix.com> wrote: > > On 17/02/2025 4:08 pm, Ross Lagerwall wrote: > > A lot of systems automatically add microcode to the initrd so it can be > > useful as a vendor policy to always scan for microcode. Add a Kconfig > > option to allow setting the default behaviour. > > > > The default behaviour is unchanged since the new option defaults to > > "no". > > > > Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> > > I'm pretty sure this is safe on 4.20. > > Prior versions of Xen need the fix to make idx/scan be mutually > exclusive, which hasn't been backported yet IIRC. > > > --- > > xen/arch/x86/Kconfig | 11 +++++++++++ > > xen/arch/x86/cpu/microcode/core.c | 2 +- > > 2 files changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig > > index 9cdd04721afa..b806d8bc3319 100644 > > --- a/xen/arch/x86/Kconfig > > +++ b/xen/arch/x86/Kconfig > > @@ -383,6 +383,17 @@ config ALTP2M > > > > If unsure, stay with defaults. > > > > +config UCODE_SCAN_DEFAULT > > + def_bool n > > + prompt "Scan for microcode by default" > > + help > > + During boot, Xen can scan the multiboot images for a CPIO archive > > + containing CPU microcode to be loaded. > > ", which is Linux's mechanism for early microcode loading." > > This is quite an important point to cover. > > > + > > + Enabling this option will cause Xen to scan for it by default. > > + > > + If unsure, say N. > > Personally I don't like this "If unsure", because it's almost always > redundant with the default. > > In this case, it really ought to be "set if you have a Linux dom0", > which in turn begs the question as to whether it ought to be bool y. > I agree with you that changing the default to yes is probably a good idea but I think it would be better to separate making it configurable from changing the default behaviour. Ross
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig index 9cdd04721afa..b806d8bc3319 100644 --- a/xen/arch/x86/Kconfig +++ b/xen/arch/x86/Kconfig @@ -383,6 +383,17 @@ config ALTP2M If unsure, stay with defaults. +config UCODE_SCAN_DEFAULT + def_bool n + prompt "Scan for microcode by default" + help + During boot, Xen can scan the multiboot images for a CPIO archive + containing CPU microcode to be loaded. + + Enabling this option will cause Xen to scan for it by default. + + If unsure, say N. + endmenu source "common/Kconfig" diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c index 87283cff1de4..de00c22b4bd6 100644 --- a/xen/arch/x86/cpu/microcode/core.c +++ b/xen/arch/x86/cpu/microcode/core.c @@ -100,7 +100,7 @@ static struct microcode_patch *microcode_cache; * location we require that they are not both active together. */ static int __initdata opt_mod_idx; -static bool __initdata opt_scan; +static bool __initdata opt_scan = IS_ENABLED(CONFIG_UCODE_SCAN_DEFAULT); /* * Used by the EFI path only, when xen.cfg identifies an explicit microcode
A lot of systems automatically add microcode to the initrd so it can be useful as a vendor policy to always scan for microcode. Add a Kconfig option to allow setting the default behaviour. The default behaviour is unchanged since the new option defaults to "no". Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> --- xen/arch/x86/Kconfig | 11 +++++++++++ xen/arch/x86/cpu/microcode/core.c | 2 +- 2 files changed, 12 insertions(+), 1 deletion(-)