From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753436AbcLFQcF (ORCPT ); Tue, 6 Dec 2016 11:32:05 -0500 Received: from 8bytes.org ([81.169.241.247]:58816 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501AbcLFQcE (ORCPT ); Tue, 6 Dec 2016 11:32:04 -0500 Date: Tue, 6 Dec 2016 17:31:11 +0100 From: Joerg Roedel To: Jacob Pan Cc: iommu@lists.linux-foundation.org, LKML , David Woodhouse , Raj Ashok , Mika Kuoppala Subject: Re: [PATCH] iommu/intel-iommu: fix pasid table size encoding Message-ID: <20161206163111.GC27203@8bytes.org> References: <1480629026-174113-1-git-send-email-jacob.jun.pan@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1480629026-174113-1-git-send-email-jacob.jun.pan@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jacob, On Thu, Dec 01, 2016 at 01:50:26PM -0800, Jacob Pan wrote: > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 27596e6..f112aa9 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -5173,6 +5173,29 @@ static void intel_iommu_remove_device(struct device *dev) > } > > #ifdef CONFIG_INTEL_IOMMU_SVM > +#define MAX_NR_PASID_BITS (20) > +static inline unsigned long intel_iommu_get_pts(struct intel_iommu *iommu) > +{ > + unsigned long pts; > + > + /* > + * Convert ecap_pss to extend context entry pts encoding, also > + * respect the soft pasid_max value set by the iommu. > + * - number of PASID bits = ecap_pss + 1 > + * - number of PASID table entries = 2^(pts + 5) > + * Therefore, pts = ecap_pss - 4 > + * e.g. KBL ecap_pss = 0x13, PASID has 20 bits, pts = 15 > + */ > + if (ecap_pss(iommu->ecap) < 5) > + return 0; > + > + pts = (ecap_pss(iommu->ecap) - 4); > + > + /* pasid_max is encoded as actual number of entries not the bits */ > + return min(find_first_bit((unsigned long *)&iommu->pasid_max, > + MAX_NR_PASID_BITS) - 5, pts); Iommu->max_pasid already depends on ecap_pss(), so I think it is better to just calculate the pts value as ffs(iommu->max_pasid) - 5. This way you don't need an extra function and have a simpler calculation. Joerg