Re: [PATCH v1 03/14] iommufd/device: Setup MSI on kernel-managed domains

Eric Auger
2023-03-10T16:46:38Z

Hi Nicolin,

On 3/9/23 11:53, Nicolin Chen wrote:
> The IOMMU_RESV_SW_MSI is a kernel-managed domain thing. So, it should be
> only setup on a kernel-managed domain only. If the attaching domain is a
> user-managed domain, redirect the hwpt to hwpt->parent to do it correctly.
>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
> drivers/iommu/iommufd/device.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index f95b558f5e95..a3e7d2889164 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -350,7 +350,8 @@ static int iommufd_group_setup_msi(struct iommufd_group *igroup,
> * call iommu_get_msi_cookie() on its behalf. This is necessary to setup
> * the MSI window so iommu_dma_prepare_msi() can install pages into our
> * domain after request_irq(). If it is not done interrupts will not
> - * work on this domain.
> + * work on this domain. And the msi_cookie should be always set into the
s/And the/The/
> + * kernel-managed (parent) domain.
> *
> * FIXME: This is conceptually broken for iommufd since we want to allow
> * userspace to change the domains, eg switch from an identity IOAS to a
> @@ -358,6 +359,8 @@ static int iommufd_group_setup_msi(struct iommufd_group *igroup,
> * matches what the IRQ layer actually expects in a newly created
> * domain.
> */
> + if (hwpt->parent)
> + hwpt = hwpt->parent;
I guess there is a garantee the parent hwpt is necessarily a
kernel-managed domain?
Is it that part of the spec that enforces it?
IOMMU_HWPT_ALLOC doc says:
" * A user-managed HWPT will be created from a given parent HWPT via
@pt_id, in
* which the parent HWPT must be allocated previously via the same ioctl
from a
* given IOAS.
"
Maybe precise that in the commit msg?

Thanks

Eric
> if (sw_msi_start != PHYS_ADDR_MAX && !hwpt->msi_cookie) {
> rc = iommu_get_msi_cookie(hwpt->domain, sw_msi_start);
> if (rc)