linux-kernel - Re: [PATCH 09/18] iommu/vt-d: Enlightened PASID allocation

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Message-ID: <20190409100859.GF9224@smile.fi.intel.com>
Date:   Tue, 9 Apr 2019 13:08:59 +0300
From:   Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        Yi Liu <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [PATCH 09/18] iommu/vt-d: Enlightened PASID allocation

On Mon, Apr 08, 2019 at 04:59:24PM -0700, Jacob Pan wrote:
> From: Lu Baolu <baolu.lu@...ux.intel.com>
> 
> If Intel IOMMU runs in caching mode, a.k.a. virtual IOMMU, the
> IOMMU driver should rely on the emulation software to allocate
> and free PASID IDs. The Intel vt-d spec revision 3.0 defines a
> register set to support this. This includes a capability register,
> a virtual command register and a virtual response register. Refer
> to section 10.4.42, 10.4.43, 10.4.44 for more information.
> 
> This patch adds the enlightened PASID allocation/free interfaces
> via the virtual command register.

> +	pr_debug("vcmd alloc pasid\n");

Perhaps tracepoints should be in use?
OTOH we have function tracer, so, this message in any case is a noise.
And this is applicable to other similar cases.

-- 
With Best Regards,
Andy Shevchenko