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[47.54.130.67]) by smtp.gmail.com with ESMTPSA id af79cd13be357-910baa3c045sm682967285a.13.2026.05.15.15.35.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 May 2026 15:35:45 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1wO18D-00000008EMQ-0W2r; Fri, 15 May 2026 19:35:45 -0300 Date: Fri, 15 May 2026 19:35:45 -0300 From: Jason Gunthorpe To: Yu Zhang Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-arch@vger.kernel.org, wei.liu@kernel.org, kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com, longli@microsoft.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, bhelgaas@google.com, kwilczynski@kernel.org, lpieralisi@kernel.org, mani@kernel.org, robh@kernel.org, arnd@arndb.de, mhklinux@outlook.com, jacob.pan@linux.microsoft.com, tgopinath@linux.microsoft.com, easwar.hariharan@linux.microsoft.com Subject: Re: [PATCH v1 4/4] iommu/hyperv: Add page-selective IOTLB flush support Message-ID: <20260515223545.GL7702@ziepe.ca> References: <20260511162408.1180069-1-zhangyu1@linux.microsoft.com> <20260511162408.1180069-5-zhangyu1@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260511162408.1180069-5-zhangyu1@linux.microsoft.com> On Tue, May 12, 2026 at 12:24:08AM +0800, Yu Zhang wrote: > +static inline u16 hv_iommu_fill_iova_list(union hv_iommu_flush_va *iova_list, > + unsigned long start, > + unsigned long end) > +{ > + unsigned long start_pfn = start >> PAGE_SHIFT; > + unsigned long end_pfn = PAGE_ALIGN(end) >> PAGE_SHIFT; > + unsigned long nr_pages = end_pfn - start_pfn; > + u16 count = 0; > + > + while (nr_pages > 0) { > + unsigned long flush_pages; > + int order; > + unsigned long pfn_align; > + unsigned long size_align; > + > + if (count >= HV_IOMMU_MAX_FLUSH_VA_COUNT) { > + count = HV_IOMMU_FLUSH_VA_OVERFLOW; > + break; > + } > + > + if (start_pfn) > + pfn_align = __ffs(start_pfn); > + else > + pfn_align = BITS_PER_LONG - 1; > + > + size_align = __fls(nr_pages); > + order = min(pfn_align, size_align); > + iova_list[count].page_mask_shift = order; > + iova_list[count].page_number = start_pfn; > + > + flush_pages = 1UL << order; > + start_pfn += flush_pages; > + nr_pages -= flush_pages; > + count++; > + } This seems like a really silly hypervisor interface. Why doesn't it just accept a normal range? Splitting it into power of two aligned ranges is very inefficient. Jason