lkml.org 
[lkml]   [2021]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: `AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y` causes AMDGPU to fail on Ryzen: amdgpu: SME is not compatible with RAVEN
    On Mon, Oct 11, 2021 at 10:21 AM Paul Menzel <pmenzel@molgen.mpg.de> wrote:
    >
    > Dear Tom,
    >
    >
    > Am 11.10.21 um 15:58 schrieb Tom Lendacky:
    > > On 10/11/21 8:52 AM, Paul Menzel wrote:
    >
    > >> Am 11.10.21 um 15:27 schrieb Tom Lendacky:
    > >>> On 10/11/21 8:11 AM, Borislav Petkov wrote:
    > >>>> On Mon, Oct 11, 2021 at 03:05:33PM +0200, Paul Menzel wrote:
    > >>>>> I think, the IOMMU is enabled on the MSI B350M MORTAR, but
    > >>>>> otherwise, yes
    > >>>>> this looks fine. The help text could also be updated to mention
    > >>>>> problems
    > >>>>> with AMD Raven devices.
    > >>>>
    > >>>> This is not only about Raven GPUs but, as Alex explained, pretty much
    > >>>> about every device which doesn't support a 48 bit DMA mask. I'll expand
    > >>>> that aspect in the changelog.
    > >>>
    > >>> In general, non-GPU devices that don't support a 48-bit DMA mask work
    > >>> fine (assuming they have set their DMA mask appropriately). It really
    > >>> depends on whether SWIOTLB will be able to satisfy the memory
    > >>> requirements of the driver when the IOMMU is not enabled or in
    > >>> passthrough mode. Since GPU devices need/use a lot of memory, that
    > >>> becomes a problem.
    > >>
    > >> How can I check that?
    > >
    > > How can you check what? 32-bit DMA devices? GPUs? I need a bit more
    > > information...
    >
    > How can I check, why MEM_ENCRYPT is not working on my device despite the
    > IOMMU being enabled.

    I think there are several potential problem cases:

    1. Device is in passthrough mode in the IOMMU and the device has a
    limited DMA mask. This could be due to a hardware requirements (e.g.,
    IOMMUv2 functionality) or a hardware/platform requirements (e.g., ACPI
    IOMMU tables define passthrough for a specific device or memory
    region). This is the case for Raven.

    2. Device driver bug (e.g., driver not using the DMA API properly)

    Alex

    >
    >
    > Kind regards,
    >
    > Paul

    \
     
     \ /
      Last update: 2021-10-11 16:34    [W:3.796 / U:0.192 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site