Messages in this thread | | | Subject | Re: [PATCH] iommu/amd: Fix unity mapping initialization race | From | Wan Zongshun <> | Date | Sun, 10 Jul 2016 19:40:53 +0800 |
| |
On 2016年07月07日 00:00, Joerg Roedel wrote: > From: Joerg Roedel <jroedel@suse.de> > > There is a race condition in the AMD IOMMU init code that > causes requested unity mappings to be blocked by the IOMMU > for a short period of time. This results on boot failures > and IO_PAGE_FAULTs on some machines. > > Fix this by making sure the unity mappings are installed > before all other DMA is blocked. > > Fixes: aafd8ba0ca74 ('iommu/amd: Implement add_device and remove_device') > Cc: stable@vger.kernel.org # v4.2+ > Signed-off-by: Joerg Roedel <jroedel@suse.de> > --- > drivers/iommu/amd_iommu_init.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c > index d091def..59741ea 100644 > --- a/drivers/iommu/amd_iommu_init.c > +++ b/drivers/iommu/amd_iommu_init.c > @@ -1568,13 +1568,23 @@ static int __init amd_iommu_init_pci(void) > break; > } > > + /* > + * Order is important here to make sure any unity map requirements are > + * fulfilled. The unity mappings are created and written to the device > + * table during the amd_iommu_init_api() call. > + * > + * After that we call init_device_table_dma() to make sure any > + * uninitialized DTE will block DMA, and in the end we flush the caches > + * of all IOMMUs to make sure the changes to the device table are > + * active. > + */
Joerg,
Do you mean we need enable the V and TV bits to DTE entry after all DTEs tables were initialized completely?
I checked this function 'init_device_table_dma', and find it just set V and TV bit, to set translation info valid and DTE bits127:1 valid.
So I just think all things it should to do are to allow DMA access, GPA-to-SPA translation should be active, why you add function comments below is to not allow DMA access and suppress all page faults?
/* * Init the device table to not allow DMA access for devices and * suppress all page faults */ static void init_device_table_dma(void)
> + ret = amd_iommu_init_api(); > + > init_device_table_dma(); > > for_each_iommu(iommu) > iommu_flush_all_caches(iommu); > > - ret = amd_iommu_init_api(); > - > if (!ret) > print_iommu_info(); > >
| |