Re: [PATCH 16/19] iommu/amd: Use roundup_pow_two() instead of get_order()
From: Robin Murphy <robin.murphy@arm.com>
Date: 2025-02-05 16:23:34
Also in:
asahi, linux-iommu, linux-patches, linux-riscv, linux-rockchip, linux-samsung-soc, linux-sunxi, linux-tegra
On 2025-02-04 6:34 pm, Jason Gunthorpe wrote:
1 << (get_order(x) + PAGE_SHIFT) == roundup_pow_two()
...unless x < 2048, which does seem possible here if last_bdf is sufficiently small. Not too significant in the cases where the result is only rounded back up again for an allocation or remap anyway, but I do wonder about the use of dev_table_size in iommu_set_device_table(), and whether this change might break it, or whether it's already wrong for that case and this might actually fix it... Thanks, Robin.
quoted hunk ↗ jump to hunk
Use the shorter version. Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> --- drivers/iommu/amd/init.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index f1c5041647173c..7d77929bc63af3 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c@@ -247,10 +247,7 @@ static void init_translation_status(struct amd_iommu *iommu) static inline unsigned long tbl_size(int entry_size, int last_bdf) { - unsigned shift = PAGE_SHIFT + - get_order((last_bdf + 1) * entry_size); - - return 1UL << shift; + return roundup_pow_of_two((last_bdf + 1) * entry_size); } int amd_iommu_get_num_iommus(void)