2023-09-18 13:26:23

by Niklas Schnelle

Subject: [PATCH v2 2/2] iommu/virtio: Add ops->flush_iotlb_all and enable deferred flush

Add ops->flush_iotlb_all operation to enable virtio-iommu for the
dma-iommu deferred flush scheme. This results in a significant increase
in performance in exchange for a window in which devices can still
access previously IOMMU mapped memory when running with
CONFIG_IOMMU_DEFAULT_DMA_LAZY. The previous strict behavior can be
achieved with iommu.strict=1 on the kernel command line or
CONFIG_IOMMU_DEFAULT_DMA_STRICT.

Link: https://lore.kernel.org/lkml/20230802123612.GA6142@myrica/
Signed-off-by: Niklas Schnelle <[email protected]>
---
drivers/iommu/virtio-iommu.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 3649586f0e5c..4dd330fbcbdd 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -926,6 +926,13 @@ static int viommu_iotlb_sync_map(struct iommu_domain *domain,
return viommu_sync_req(vdomain->viommu);
}

+static void viommu_flush_iotlb_all(struct iommu_domain *domain)
+{
+ struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+ viommu_sync_req(vdomain->viommu);
+}
+
static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
{
struct iommu_resv_region *entry, *new_entry, *msi = NULL;
@@ -1051,6 +1058,8 @@ static bool viommu_capable(struct device *dev, enum iommu_cap cap)
switch (cap) {
case IOMMU_CAP_CACHE_COHERENCY:
return true;
+ case IOMMU_CAP_DEFERRED_FLUSH:
+ return true;
default:
return false;
}
@@ -1071,6 +1080,7 @@ static struct iommu_ops viommu_ops = {
.map_pages = viommu_map_pages,
.unmap_pages = viommu_unmap_pages,
.iova_to_phys = viommu_iova_to_phys,
+ .flush_iotlb_all = viommu_flush_iotlb_all,
.iotlb_sync = viommu_iotlb_sync,
.iotlb_sync_map = viommu_iotlb_sync_map,
.free = viommu_domain_free,

--
2.39.2

2023-09-18 18:07:22

by Jean-Philippe Brucker

Subject: Re: [PATCH v2 2/2] iommu/virtio: Add ops->flush_iotlb_all and enable deferred flush

On Mon, Sep 18, 2023 at 01:51:44PM +0200, Niklas Schnelle wrote:
> Add ops->flush_iotlb_all operation to enable virtio-iommu for the
> dma-iommu deferred flush scheme. This results in a significant increase
> in performance in exchange for a window in which devices can still
> access previously IOMMU mapped memory when running with
> CONFIG_IOMMU_DEFAULT_DMA_LAZY. The previous strict behavior can be
> achieved with iommu.strict=1 on the kernel command line or
> CONFIG_IOMMU_DEFAULT_DMA_STRICT.
>
> Link: https://lore.kernel.org/lkml/20230802123612.GA6142@myrica/
> Signed-off-by: Niklas Schnelle <[email protected]>

Reviewed-by: Jean-Philippe Brucker <[email protected]>

> ---
> drivers/iommu/virtio-iommu.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index 3649586f0e5c..4dd330fbcbdd 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -926,6 +926,13 @@ static int viommu_iotlb_sync_map(struct iommu_domain *domain,
> return viommu_sync_req(vdomain->viommu);
> }
>
> +static void viommu_flush_iotlb_all(struct iommu_domain *domain)
> +{
> + struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> + viommu_sync_req(vdomain->viommu);
> +}
> +
> static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
> {
> struct iommu_resv_region *entry, *new_entry, *msi = NULL;
> @@ -1051,6 +1058,8 @@ static bool viommu_capable(struct device *dev, enum iommu_cap cap)
> switch (cap) {
> case IOMMU_CAP_CACHE_COHERENCY:
> return true;
> + case IOMMU_CAP_DEFERRED_FLUSH:
> + return true;
> default:
> return false;
> }
> @@ -1071,6 +1080,7 @@ static struct iommu_ops viommu_ops = {
> .map_pages = viommu_map_pages,
> .unmap_pages = viommu_unmap_pages,
> .iova_to_phys = viommu_iova_to_phys,
> + .flush_iotlb_all = viommu_flush_iotlb_all,
> .iotlb_sync = viommu_iotlb_sync,
> .iotlb_sync_map = viommu_iotlb_sync_map,
> .free = viommu_domain_free,
>
> --
> 2.39.2
>