linux-kernel - Re: [EXTERNAL] Re: [PATCH] x86/ioapic: Don't return 0 as valid virq

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Date:   Mon, 13 Mar 2023 12:14:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Saurabh Singh Sengar <ssengar@...rosoft.com>
Cc:     Saurabh Sengar <ssengar@...ux.microsoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "johan+linaro@...nel.org" <johan+linaro@...nel.org>,
        "isaku.yamahata@...el.com" <isaku.yamahata@...el.com>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rahul.tanwar@...ux.intel.com" <rahul.tanwar@...ux.intel.com>,
        "andriy.shevchenko@...el.com" <andriy.shevchenko@...el.com>
Subject: Re: [EXTERNAL] Re: [PATCH] x86/ioapic: Don't return 0 as valid virq

On Mon, Mar 13, 2023 at 03:29:32AM +0000, Saurabh Singh Sengar wrote:
> To be specific in our system which is a guest VM we don't need IO-APIC and hence
> there is no device tree node for it. It is observed that we get irq 0 assigned to PCI-MSI.

This should be added to your commit message: what guest VM is that and
why should the kernel support it.

Why doesn't it need an IO-APIC and why does the current code need to be
changed just for your guest VM?

What else needs to be changed so that your VM works?

Where is that VM's documentation and why can't that VM be fixed *not* to
need kernel changes? IOW, why can't that VM emulate an IO-APIC like the
others do...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette