On Tue, Aug 01, 2017 at 07:37:26PM +0800, Baoquan He wrote: > AMD pointed out it's unsafe to update the device-table while iommu > is enabled. It turns out that device-table pointer update is split > up into two 32bit writes in the IOMMU hardware. So updating it while > the IOMMU is enabled could have some nasty side effects. > > The safe way to work around this is to always allocate the device-table > below 4G, including the old device-table in normal kernel and the > device-table used for copying the content of the old device-table in kdump > kernel. Meanwhile we need check if the address of old device-table is > above 4G because it might has been touched accidentally in corrupted > 1st kernel. > > Signed-off-by: Baoquan He <b...@redhat.com> > --- > drivers/iommu/amd_iommu_init.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c > index 6a77b99d08e4..8c6431ac5698 100644 > --- a/drivers/iommu/amd_iommu_init.c > +++ b/drivers/iommu/amd_iommu_init.c > @@ -882,11 +882,15 @@ static int copy_device_table(void) > continue; > > old_devtb_phys = entry & PAGE_MASK; > + if (old_devtb_phys > 0x100000000ULL) {
Needs to be '>='. > + pr_err("The address of old device table is above 4G, > not trustworthy!/n"); > + return -1; > + } Okay, forget my previous comment about it, the check is added here _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu