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Manjarres" To: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org Subject: [RFC PATCH v4 05/15] iommu: Use bitmap to calculate page size in iommu_pgsize() Date: Wed, 7 Apr 2021 21:52:31 -0700 Message-Id: <20210408045241.27316-6-isaacm@codeaurora.org> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20210408045241.27316-1-isaacm@codeaurora.org> References: <20210408045241.27316-1-isaacm@codeaurora.org> MIME-Version: 1.0 Cc: "Isaac J . Manjarres" , robin.murphy@arm.com, Will Deacon , pratikp@codeaurora.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" From: Will Deacon Avoid the potential for shifting values by amounts greater than the width of their type by using a bitmap to compute page size in iommu_pgsize(). Signed-off-by: Will Deacon Signed-off-by: Isaac J. Manjarres --- drivers/iommu/iommu.c | 31 ++++++++++++------------------- 1 file changed, 12 insertions(+), 19 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index d0b0a15dba84..bcd623862bf9 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -8,6 +8,7 @@ #include #include +#include #include #include #include @@ -2360,30 +2361,22 @@ static size_t iommu_pgsize(struct iommu_domain *domain, unsigned long addr_merge, size_t size) { unsigned int pgsize_idx; + unsigned long pgsizes; size_t pgsize; - /* Max page size that still fits into 'size' */ - pgsize_idx = __fls(size); + /* Page sizes supported by the hardware and small enough for @size */ + pgsizes = domain->pgsize_bitmap & GENMASK(__fls(size), 0); - /* need to consider alignment requirements ? */ - if (likely(addr_merge)) { - /* Max page size allowed by address */ - unsigned int align_pgsize_idx = __ffs(addr_merge); - pgsize_idx = min(pgsize_idx, align_pgsize_idx); - } - - /* build a mask of acceptable page sizes */ - pgsize = (1UL << (pgsize_idx + 1)) - 1; - - /* throw away page sizes not supported by the hardware */ - pgsize &= domain->pgsize_bitmap; + /* Constrain the page sizes further based on the maximum alignment */ + if (likely(addr_merge)) + pgsizes &= GENMASK(__ffs(addr_merge), 0); - /* make sure we're still sane */ - BUG_ON(!pgsize); + /* Make sure we have at least one suitable page size */ + BUG_ON(!pgsizes); - /* pick the biggest page */ - pgsize_idx = __fls(pgsize); - pgsize = 1UL << pgsize_idx; + /* Pick the biggest page size remaining */ + pgsize_idx = __fls(pgsizes); + pgsize = BIT(pgsize_idx); return pgsize; } -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu