linux-kernel - Re: [patch 3/8] PCI/MSI: Enforce that MSI-X table entry is masked for update

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Date:   Thu, 22 Jul 2021 00:59:19 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Raj\, Ashok" <ashok.raj@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Marc Zyngier <maz@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        x86@...nel.org, Ashok Raj <ashok.raj@...el.com>
Subject: Re: [patch 3/8] PCI/MSI: Enforce that MSI-X table entry is masked for update

Ashok,

On Wed, Jul 21 2021 at 15:32, Ashok Raj wrote:
> On Wed, Jul 21, 2021 at 09:11:29PM +0200, Thomas Gleixner wrote:
>> +		/*
>> +		 * The specification mandates that the entry is masked
>> +		 * when the message is modified:
>> +		 *
>> +		 * "If software changes the Address or Data value of an
>> +		 * entry while the entry is unmasked, the result is
>> +		 * undefined."
>> +		 */
>> +		if (unmasked)
>> +			__pci_msix_desc_mask_irq(entry, PCI_MSIX_ENTRY_CTRL_MASKBIT);
>> +
>
> Is there any locking needs here? say during cpu hotplug and some user-space
> setting affinity?

No. Except for suspend/resume this is always serialized by irq_desc::lock().

Thanks,

        tglx