linux-kernel - Re: [PATCH RFC 12/13] iommu/vt-d: Add a helper to retrieve PID address

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Message-ID: <874jgvuls0.ffs@tglx>
Date:   Wed, 06 Dec 2023 21:19:11 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>,
        iommu@...ts.linux.dev, Lu Baolu <baolu.lu@...ux.intel.com>,
        kvm@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, maz@...nel.org,
        peterz@...radead.org, seanjc@...gle.com,
        Robin Murphy <robin.murphy@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH RFC 12/13] iommu/vt-d: Add a helper to retrieve PID address

On Sat, Nov 11 2023 at 20:16, Jacob Pan wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
>
> When programming IRTE for posted mode, we need to retrieve the
> physical

we need .... I surely did not write this changelog.

> address of the posted interrupt descriptor (PID) that belongs to it's
> target CPU.
>
> This per CPU PID has already been set up during cpu_init().

This information is useful because?

> +static u64 get_pi_desc_addr(struct irq_data *irqd)
> +{
> +	int cpu = cpumask_first(irq_data_get_effective_affinity_mask(irqd));

The effective affinity mask is magically correct when this is called?