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To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        Shuah Khan <shuah@kernel.org>, Jonathan Corbet <corbet@lwn.net>
Cc:     "H . Peter Anvin" <hpa@zytor.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Dionna Amalie Glaze <dionnaglaze@google.com>,
        Chong Cai <chongc@google.com>, Qinkun Bao <qinkun@apache.org>,
        Guorui Yu <GuoRui.Yu@linux.alibaba.com>,
        Du Fan <fan.du@intel.com>, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v3 1/3] x86/tdx: Add TDX Guest event notify interrupt
 support
In-Reply-To: <83a832b156f6e3bf906fee657b0147f042481a36.1684048511.git.sathyanarayanan.kuppuswamy@linux.intel.com>
References: <cover.1684048511.git.sathyanarayanan.kuppuswamy@linux.intel.com>
 <83a832b156f6e3bf906fee657b0147f042481a36.1684048511.git.sathyanarayanan.kuppuswamy@linux.intel.com>
Date:   Wed, 23 Aug 2023 22:47:56 +0200
Message-ID: <875y55eb9f.ffs@tglx>
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List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sun, May 14 2023 at 00:23, Kuppuswamy Sathyanarayanan wrote:
> +static int __init tdx_event_irq_init(void)
> +{
> +	struct irq_affinity_desc desc;
> +	struct irq_alloc_info info;
> +	struct irq_cfg *cfg;
> +	int irq;
> +
> +	if (!cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> +		return 0;
> +
> +	init_irq_alloc_info(&info, NULL);
> +
> +	cpumask_set_cpu(smp_processor_id(), &desc.mask);

desc is completely uninitialized here and therefore desc.mask and
desc.is_managed contain random stack content.

The only reason why this "works" is that tdx_event_irq_init() is an
early initcall which is invoked before SMP init, so the only choice of
the allocator is to pick an interrupt on CPU0.

Thanks,

        tglx