Re: [PATCH V5 1/5] iommu/amd: Remove unnecessary locking from AMD iommu driver
From: Christoph Hellwig <hch@infradead.org>
Date: 2019-08-20 09:41:52
Also in:
linux-arm-msm, linux-iommu, linux-mediatek, linux-rockchip, linux-s390, linux-samsung-soc, linux-tegra, lkml
On Thu, Aug 15, 2019 at 12:09:39PM +0100, Tom Murphy wrote:
We can remove the mutex lock from amd_iommu_map and amd_iommu_unmap. iommu_map doesn’t lock while mapping and so no two calls should touch the same iova range. The AMD driver already handles the page table page allocations without locks so we can safely remove the locks.
I've been looking over the code and trying to understand how the synchronization works. I gues we the cmpxchg64 in free_clear_pte is the important point here? I have to admit I don't fully understand the concurrency issues here, but neither do I understand what the mutex you removed might have helped to start with. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel