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[34.83.136.168]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c743a8186efsm2341998a12.13.2026.03.20.11.56.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Mar 2026 11:56:52 -0700 (PDT) Date: Fri, 20 Mar 2026 18:56:48 +0000 From: Samiullah Khawaja To: Pranjal Shrivastava Cc: Vipin Sharma , David Woodhouse , Lu Baolu , Joerg Roedel , Will Deacon , Jason Gunthorpe , Robin Murphy , Kevin Tian , Alex Williamson , Shuah Khan , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Saeed Mahameed , Adithya Jayachandran , Parav Pandit , Leon Romanovsky , William Tu , Pratyush Yadav , Pasha Tatashin , David Matlack , Andrew Morton , Chris Li , YiFei Zhu Subject: Re: [PATCH 04/14] iommu/pages: Add APIs to preserve/unpreserve/restore iommu pages Message-ID: References: <20260203220948.2176157-1-skhawaja@google.com> <20260203220948.2176157-5-skhawaja@google.com> <20260317202925.GA2582517.vipinsh@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Fri, Mar 20, 2026 at 11:01:25AM +0000, Pranjal Shrivastava wrote: >On Tue, Mar 17, 2026 at 01:59:03PM -0700, Vipin Sharma wrote: >> On Tue, Feb 03, 2026 at 10:09:38PM +0000, Samiullah Khawaja wrote: >> > + > >[------- snip >8 --------] > >> > +EXPORT_SYMBOL_GPL(iommu_unpreserve_pages); >> > + >> > +void iommu_restore_page(u64 phys) >> > +{ >> > + struct ioptdesc *iopt; >> > + struct folio *folio; >> > + unsigned long pgcnt; >> > + unsigned int order; >> > + >> > + folio = kho_restore_folio(phys); >> > + BUG_ON(!folio); >> > + >> > + iopt = folio_ioptdesc(folio); >> > + >> > + order = folio_order(folio); >> > + pgcnt = 1UL << order; >> > + mod_node_page_state(folio_pgdat(folio), NR_IOMMU_PAGES, pgcnt); >> > + lruvec_stat_mod_folio(folio, NR_SECONDARY_PAGETABLE, pgcnt); >> >> Above two functions are also used in other two places in this file, lets >> create a common function for these two operations. >> > >I was thinking about this, out of the 2 other places one is >`__iommu_free_desc` where we are supposed to subtract pgcnt.. but I >think we can follow the -pgcnt pattern we have currently and add a >helper `iommu_folio_update_stats(folio, pgcnt)` where we can pass -pgcnt >to subtract nr_pages? Something like: > >+static inline void iommu_folio_update_stats(struct folio *folio, long nr_pages) >+{ >+ mod_node_page_state(folio_pgdat(folio), NR_IOMMU_PAGES, nr_pages); >+ lruvec_stat_mod_folio(folio, NR_SECONDARY_PAGETABLE, nr_pages); >+} > >@@ -86,8 +91,7 @@ static void __iommu_free_desc(struct ioptdesc *iopt) > if (IOMMU_PAGES_USE_DMA_API) > WARN_ON_ONCE(iopt->incoherent); > >- mod_node_page_state(folio_pgdat(folio), NR_IOMMU_PAGES, -pgcnt); >- lruvec_stat_mod_folio(folio, NR_SECONDARY_PAGETABLE, -pgcnt); >+ iommu_folio_update_stats(folio, -(long)pgcnt); > folio_put(folio); > } > >But I'm unsure if passing -(long)pgcnt is a good idea? mod_node_page_state() takes last argument as "long" and I can see other examples of passing -folio_nr_pages(folio) directly into it. So we can just keep it as following: iommu_folio_update_stats(folio, -pgcnt); I think it is a good cleanup. I will update this in the next revision. > >> > +} >> > +EXPORT_SYMBOL_GPL(iommu_restore_page); >> > + > >Thanks, >Praan