[PATCH] iommu/amd: flush IOTLB for specific domains only

[Daniel Drake]

Hi Arindam,

You CC'd me on this - does this mean that it is a fix for the issue
described in the thread "amd-iommu: can't boot with amdgpu, AMD-Vi:
Completion-Wait loop timed out" ?

Thanks
Daniel


On Mon, Mar 27, 2017 at 12:17 AM,  <arindam.nath at amd.com> wrote:
> From: Arindam Nath <arindam.nath at amd.com>
>
> The idea behind flush queues is to defer the IOTLB flushing
> for domains for which the mappings are no longer valid. We
> add such domains in queue_add(), and when the queue size
> reaches FLUSH_QUEUE_SIZE, we perform __queue_flush().
>
> Since we have already taken lock before __queue_flush()
> is called, we need to make sure the IOTLB flushing is
> performed as quickly as possible.
>
> In the current implementation, we perform IOTLB flushing
> for all domains irrespective of which ones were actually
> added in the flush queue initially. This can be quite
> expensive especially for domains for which unmapping is
> not required at this point of time.
>
> This patch makes use of domain information in
> 'struct flush_queue_entry' to make sure we only flush
> IOTLBs for domains who need it, skipping others.
>
> Signed-off-by: Arindam Nath <arindam.nath at amd.com>
> ---
>  drivers/iommu/amd_iommu.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 98940d1..6a9a048 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2227,15 +2227,16 @@ static struct iommu_group *amd_iommu_device_group(struct device *dev)
>
>  static void __queue_flush(struct flush_queue *queue)
>  {
> -       struct protection_domain *domain;
> -       unsigned long flags;
>         int idx;
>
> -       /* First flush TLB of all known domains */
> -       spin_lock_irqsave(&amd_iommu_pd_lock, flags);
> -       list_for_each_entry(domain, &amd_iommu_pd_list, list)
> -               domain_flush_tlb(domain);
> -       spin_unlock_irqrestore(&amd_iommu_pd_lock, flags);
> +       /* First flush TLB of all domains which were added to flush queue */
> +       for (idx = 0; idx < queue->next; ++idx) {
> +               struct flush_queue_entry *entry;
> +
> +               entry = queue->entries + idx;
> +
> +               domain_flush_tlb(&entry->dma_dom->domain);
> +       }
>
>         /* Wait until flushes have completed */
>         domain_flush_complete(NULL);
> --
> 1.9.1
>