linux-kernel - Re: [PATCH] Use x2apic_supported() in the default_apic_id

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1331846504.16101.12.camel@sbsiddha-desk.sc.intel.com>
Date:	Thu, 15 Mar 2012 14:21:44 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Steffen Persvold <sp@...ascale.com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Daniel J Blueman <daniel@...ascale-asia.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] Use x2apic_supported() in the default_apic_id_valid()
 function.

On Thu, 2012-03-15 at 13:23 -0700, Yinghai Lu wrote:
> On Thu, Mar 15, 2012 at 11:03 AM, Steffen Persvold <sp@...ascale.com> wrote:
> > Use x2apic_supported() in the default_apic_id_valid() function. If x2apic mode is disabled (via nox2apic for example), x2apic_supported() will return false.
> >
> > This allows us to substitute the check in arch/x86/kernel/acpi/boot.c::acpi_parse_x2apic and avoid feigning the x2apic cpu feature in the NumaChip apic code.
> >
> > Signed-off-by: Steffen Persvold <sp@...ascale.com>
> > Reviewed-by: Daniel J Blueman <daniel@...ascale-asia.com>
> 
> I double checked on system with x2apic preenabled,
> nox2apic in boot command line still works well and it
> skips starting APs with apic id > 255.
> 
> Acked-by: Yinghai Lu <yinghai@...nel.org>

This breaks the smpboot check if enabling interrupt-remapping/x2apic
fails on a platform. We will be in xapic mode and we don't clear the
x2apic cpufeature bit in this case and as such smpboot check will fail.

So this change breaks the commit
c284b42abadbb22083bfde24d308899c08d44ffa.

I think the right thing is to have two different apid_id_valid checks
one for xapic driver (apic_flat_64.c) and another for x2apic driver
(x2apic_phys/cluster.c) and that way, x2apic MADT entries will be parsed
only if bios has handed over the OS in x2apic mode or if we have
selected the numachip model.

thanks,
suresh


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/