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Mon, 17 Feb 2025 11:33:26 -0800 (PST) X-Google-Smtp-Source: AGHT+IFf69rFpHRBRUkpc6IQnX+RrUwLEtxZ5WL2tBVyd6sRG7DiWOFIsmQLCd6imqOjjp0RP03prA== X-Received: by 2002:a05:6602:6408:b0:855:505:e2c5 with SMTP id ca18e2360f4ac-8557a0c198emr258969839f.2.1739820806146; Mon, 17 Feb 2025 11:33:26 -0800 (PST) Received: from redhat.com ([38.15.36.11]) by smtp.gmail.com with ESMTPSA id ca18e2360f4ac-85566f8f7f6sm203761239f.42.2025.02.17.11.33.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Feb 2025 11:33:24 -0800 (PST) Date: Mon, 17 Feb 2025 12:33:20 -0700 From: Alex Williamson To: Matthew Wilcox Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, peterx@redhat.com, mitchell.augustin@canonical.com, clg@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH 5/5] vfio/type1: Use mapping page mask for pfnmaps Message-ID: <20250217123320.051fad67.alex.williamson@redhat.com> In-Reply-To: References: <20250205231728.2527186-1-alex.williamson@redhat.com> <20250205231728.2527186-6-alex.williamson@redhat.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 5zhnH_8fzF9em6RI4g3CeKtDeJLl41Jtwj0rwGACd2M_1739820806 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 2D559100002 X-Stat-Signature: sqf5xjj9dkdo5daz3pqpmonysb7g8xzh X-HE-Tag: 1739820809-651814 X-HE-Meta: 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 d1oXGcjj yfYuptMAFXGfK+rE1Zm0SdvzaGUyRG/NXWTDgVgZEAgTySqsgRdKxpVUBB+6Eev4ZdQuilq3Lopwo7dsWxY/bbkai6fnqfHqG2Kr31xull/Y/C56gey7nyMlLQXbtUgoAdAYn2M53/fY0/QvLW16nmaqCu4lb0LzZcaH3fTz5HfwkKvL3bj1LHMDkx4wJkEVRVrESOowIXnzIDf/6KgPz1dAR54OlDs9OzQRggRUT7MZDuuK7DkMoDRJq9DXWoIQN/8mlx6SkuFM/RHdoeNM+U5m/b6u41Z039C1OyhoWueqCCedofSJgW4Yyb+1g+lmp/4jW9p8noxykWlWXiS+/zJZe6M6m34sXuGlDNclVH0geTnupqlqURlDvy47Y1LrJkRJgK+sLQr5361A= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000074, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 14 Feb 2025 19:46:22 +0000 Matthew Wilcox wrote: > On Wed, Feb 05, 2025 at 04:17:21PM -0700, Alex Williamson wrote: > > + if (is_invalid_reserved_pfn(*pfn)) { > > + unsigned long epfn; > > + > > + epfn = (((*pfn << PAGE_SHIFT) + ~pgmask + 1) > > + & pgmask) >> PAGE_SHIFT; > > + ret = min_t(int, npages, epfn - *pfn); > > You've really made life hard for yourself by passing around a page mask > instead of an order (ie 0/PMD_ORDER/PUD_ORDER). Why not: > > epfn = round_up(*pfn + 1, 1 << order); > > Although if you insist on passing around a mask, this could be: > > unsigned long sz = (~pgmask >> PAGE_SHIFT) + 1; > unsigned long epfn = round_up(*pfn + 1, sz) > Hey Willy! I was wishing I had an order, but I didn't want to mangle follow_pfnmap_start() and follow_pfnmap_setup() too much. Currently the latter is doing: args->pfn = pfn_base + ((args->address & ~addr_mask) >> PAGE_SHIFT); If follow_pfnmap_start() passed an order, this would need to change to something equivalent to: args->pfn = pfn_base + ((args->address >> PAGE_SHIFT) & ((1UL << order) - 1)); Looks pretty ugly as well, so maybe I'm just shifting the ugliness around, or maybe someone can spot a more elegant representation. Thanks, Alex