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

[Colin Ian King]

On 23/02/2021 16:36, Andrea Righi 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) {
> 

This makes sense. Thanks Andrea.

Acked-by: Colin Ian King <colin.king at canonical.com>