ACK: [SRU][X/aws][PATCH 1/1] Revert "iommu/vt-d: Gracefully handle DMAR units with no supported address widths"

Guilherme Piccoli gpiccoli at canonical.com
Tue Feb 23 17:11:51 UTC 2021


On Tue, Feb 23, 2021 at 1:36 PM Andrea Righi <andrea.righi at canonical.com> wrote:
>
> BugLink: https://bugs.launchpad.net/bugs/1913739
>
> This reverts commit 561ef22a7d396289a1c5a1d18057ccdf9bb59826.
>
> It seems that this patch is addressing the problem correctly only with
> kernels >4.4. For now it is probably safer to simply drop this patch and
> revert this change in 4.4 to avoid introducing potential regressions.
>
> Signed-off-by: Andrea Righi <andrea.righi at canonical.com>
> ---
>  drivers/iommu/dmar.c | 45 ++++++++++++++------------------------------
>  1 file changed, 14 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> index 78174f2f9fafb..00169c9eb3eed 100644
> --- a/drivers/iommu/dmar.c
> +++ b/drivers/iommu/dmar.c
> @@ -1012,8 +1012,8 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
>  {
>         struct intel_iommu *iommu;
>         u32 ver, sts;
> -       int agaw = -1;
> -       int msagaw = -1;
> +       int agaw = 0;
> +       int msagaw = 0;
>         int err;
>
>         if (!drhd->reg_base_addr) {
> @@ -1038,28 +1038,17 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
>         }
>
>         err = -EINVAL;
> -       if (cap_sagaw(iommu->cap) == 0) {
> -               pr_info("%s: No supported address widths. Not attempting DMA translation.\n",
> -                       iommu->name);
> -               drhd->ignored = 1;
> +       agaw = iommu_calculate_agaw(iommu);
> +       if (agaw < 0) {
> +               pr_err("Cannot get a valid agaw for iommu (seq_id = %d)\n",
> +                       iommu->seq_id);
> +               goto err_unmap;
>         }
> -
> -       if (!drhd->ignored) {
> -               agaw = iommu_calculate_agaw(iommu);
> -               if (agaw < 0) {
> -                       pr_err("Cannot get a valid agaw for iommu (seq_id = %d)\n",
> -                              iommu->seq_id);
> -                       drhd->ignored = 1;
> -               }
> -       }
> -       if (!drhd->ignored) {
> -               msagaw = iommu_calculate_max_sagaw(iommu);
> -               if (msagaw < 0) {
> -                       pr_err("Cannot get a valid max agaw for iommu (seq_id = %d)\n",
> -                              iommu->seq_id);
> -                       drhd->ignored = 1;
> -                       agaw = -1;
> -               }
> +       msagaw = iommu_calculate_max_sagaw(iommu);
> +       if (msagaw < 0) {
> +               pr_err("Cannot get a valid max agaw for iommu (seq_id = %d)\n",
> +                       iommu->seq_id);
> +               goto err_unmap;
>         }
>         iommu->agaw = agaw;
>         iommu->msagaw = msagaw;
> @@ -1088,12 +1077,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
>
>         drhd->iommu = iommu;
>
> -       /*
> -        * This is only for hotplug; at boot time intel_iommu_enabled won't
> -        * be set yet. When intel_iommu_init() runs, it registers the units
> -        * present at boot time, then sets intel_iommu_enabled.
> -        */
> -       if (intel_iommu_enabled && !drhd->ignored)
> +       if (intel_iommu_enabled)
>                 iommu->iommu_dev = iommu_device_create(NULL, iommu,
>                                                        intel_iommu_groups,
>                                                        "%s", iommu->name);
> @@ -1111,8 +1095,7 @@ error:
>
>  static void free_iommu(struct intel_iommu *iommu)
>  {
> -       if (intel_iommu_enabled && iommu->iommu_dev)
> -               iommu_device_destroy(iommu->iommu_dev);
> +       iommu_device_destroy(iommu->iommu_dev);
>
>         if (iommu->irq) {
>                 if (iommu->pr_irq) {
> --
> 2.30.0
>

Thanks Andrea, a clean patch, with reasonable justification.

Acked-by: Guilherme G. Piccoli <gpiccoli at canonical.com>



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