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Date: Wed, 9 Nov 2016 17:03:24 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Charles (Chas) Williams" <ciwillia@brocade.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        "M. Vefa Bicakci" <m.v.b@runbox.com>, Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH] x86/cpuid: Deal with broken firmware once more
Message-ID: <20161109160324.GR3142@twins.programming.kicks-ass.net>
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On Wed, Nov 09, 2016 at 04:35:51PM +0100, Thomas Gleixner wrote:
> Both ACPI and MP specifications require that the APIC id in the respective
> tables must be the same as the APIC id in CPUID. 
> 
> The kernel retrieves the physical package id from the APIC id during the
> ACPI/MP table scan and builds the physical to logical package map.
> 
> There exist Virtualbox and Xen implementations which violate the spec. As a

ISTR it was VMware, not VirtualBox, but whatever.. they're both crazy
virt stuff.

>  /*
> + * The physical to logical package id mapping is initialized from the
> + * acpi/mptables information. Make sure that CPUID actually agrees with
> + * that.
> + */
> +static void sanitize_package_id(struct cpuinfo_x86 *c)
> +{
> +#ifdef CONFIG_SMP
> +	unsigned int pkg, apicid, cpu = smp_processor_id();
> +
> +	apicid = apic->cpu_present_to_apicid(cpu);
> +	pkg = apicid >> boot_cpu_data.x86_coreid_bits;
> +
> +	if (apicid != c->initial_apicid) {
> +		pr_err(FW_BUG "CPU%u: APIC id mismatch. Firmware: %x CPUID: %x\n",
> +		       cpu, apicid, c->initial_apicid);

Should we not also 'fix' c->initial_apicid ?

> +	}
> +	if (pkg != c->phys_proc_id) {
> +		pr_err(FW_BUG "CPU%u: Using firmware package id %u instead of %u\n",
> +		       cpu, pkg, c->phys_proc_id);
> +		c->phys_proc_id = pkg;
> +	}
> +	c->logical_proc_id = topology_phys_to_logical_pkg(pkg);
> +#else
> +	c->locical_proc_id = 0;

UP FTW ;-)

> +#endif
> +}