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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Juergen Gross <jgross@suse.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     x86@kernel.org, Andrew Cooper <andrew.cooper3@citrix.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Wei Liu <wei.liu@kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Peter Keresztes Schmidt <peter@keresztesschmidt.de>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: Re: [patch V2 16/58] x86/apic: Sanitize num_processors handling
In-Reply-To: <d232e50f-01fc-ef2e-db29-3f790d960c0e@suse.com>
References: <20230724131206.500814398@linutronix.de>
 <20230724132045.555787669@linutronix.de>
 <d232e50f-01fc-ef2e-db29-3f790d960c0e@suse.com>
Date:   Mon, 31 Jul 2023 14:50:07 +0200
Message-ID: <87y1iwnt34.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Mon, Jul 31 2023 at 12:17, Juergen Gross wrote:
> On 24.07.23 15:34, Thomas Gleixner wrote:
> This is introducing a regression for Xen PV guests: those have no ACPI
> tables, so smp_found_config will be 0. OTOH num_processors has been set
> already using hypervisor data, so setting num_processors to 1 here will
> overwrite the previous setting.
>
> Below diff on top is fixing the problem:

Fixing? You can't be serious about that.

Why can't XENPV pretend that it has a smp configuration detected,
i.e. setting smp_found_config as any other special get_smp_config()
implementation does?

XENPV is already a major pain to deal with. No need to expand the
related insanity all over the place.

Thanks,

        tglx