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Miller" , iommu@lists.linux-foundation.org (open list:DMA MAPPING HELPERS), netdev@vger.kernel.org (open list:NETWORKING [GENERAL]) Subject: [PATCH 2/2] swiotlb: Return consistent SWIOTLB segments/nr_tbl Date: Tue, 11 Jun 2019 10:58:25 -0700 Message-Id: <20190611175825.572-3-f.fainelli@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190611175825.572-1-f.fainelli@gmail.com> References: <20190611175825.572-1-f.fainelli@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With a specifically contrived memory layout where there is no physical memory available to the kernel below the 4GB boundary, we will fail to perform the initial swiotlb_init() call and set no_iotlb_memory to true. There are drivers out there that call into swiotlb_nr_tbl() to determine whether they can use the SWIOTLB. With the right DMA_BIT_MASK() value for these drivers (say 64-bit), they won't ever need to hit swiotlb_tbl_map_single() so this can go unoticed and we would be possibly lying about those drivers. Signed-off-by: Florian Fainelli --- kernel/dma/swiotlb.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index b2b5c5df273c..e906ef2e6315 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -129,15 +129,17 @@ setup_io_tlb_npages(char *str) } early_param("swiotlb", setup_io_tlb_npages); +static bool no_iotlb_memory; + unsigned long swiotlb_nr_tbl(void) { - return io_tlb_nslabs; + return unlikely(no_iotlb_memory) ? 0 : io_tlb_nslabs; } EXPORT_SYMBOL_GPL(swiotlb_nr_tbl); unsigned int swiotlb_max_segment(void) { - return max_segment; + return unlikely(no_iotlb_memory) ? 0 : max_segment; } EXPORT_SYMBOL_GPL(swiotlb_max_segment); @@ -160,8 +162,6 @@ unsigned long swiotlb_size_or_default(void) return size ? size : (IO_TLB_DEFAULT_SIZE); } -static bool no_iotlb_memory; - void swiotlb_print_info(void) { unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT; -- 2.17.1