On 07/31/17 at 12:21pm, Joerg Roedel wrote: > Hi Baoquan, > > On Mon, Jul 31, 2017 at 06:15:30PM +0800, Baoquan He wrote: > > I plan to add GFP_DMA32 when allocate amd_iommu_dev_table in > > early_amd_iommu_init() as below. Then in kdump kernel we don't need to > > worry if the old amd_iommu_dev_table could be above 4G, right? And might > > not need to check if it's above 4G, right? > > > > diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c > > index 781a138..85d6445 100644 > > --- a/drivers/iommu/amd_iommu_init.c > > +++ b/drivers/iommu/amd_iommu_init.c > > @@ -2436,7 +2436,8 @@ static int __init early_amd_iommu_init(void) > > > > /* Device table - directly used by all IOMMUs */ > > ret = -ENOMEM; > > - amd_iommu_dev_table = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, > > + amd_iommu_dev_table = (void *)__get_free_pages( > > + GFP_KERNEL | __GFP_ZERO | GFP_DMA32, > > get_order(dev_table_size)); > > if (amd_iommu_dev_table == NULL) > > goto out; > > Yeah, adding GFP_DMA32 is right. But you still need to check it in the > kdump path. Not checking it would mean you trust the old kernel, but > since it paniced there is no reason to put any trust in what happened > before.
You are right, it could be touched accidentally. It must be checked. Thanks a lot for your answer!
