linux-kernel - RE: [PATCH 1/3] iommufd: Remove IOMMUFD_PAGE_RESP

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Message-ID: <BN9PR11MB5276DF9FD2A752CBDAE522938CA42@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Wed, 10 Jul 2024 09:45:35 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Jason Gunthorpe <jgg@...pe.ca>,
	"Joerg Roedel" <joro@...tes.org>, Will Deacon <will@...nel.org>, Robin Murphy
	<robin.murphy@....com>, Nicolin Chen <nicolinc@...dia.com>, "Liu, Yi L"
	<yi.l.liu@...el.com>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/3] iommufd: Remove IOMMUFD_PAGE_RESP_FAILURE

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Wednesday, July 10, 2024 4:34 PM
> 
> The response code of IOMMUFD_PAGE_RESP_FAILURE was defined to be
> equivalent to the "Response Failure" in PCI spec, section 10.4.2.1.
> This response code indicates that one or more pages within the
> associated request group have encountered or caused an unrecoverable
> error. Therefore, this response disables the PRI at the function.
> 
> Modern I/O virtualization technologies, like SR-IOV, share PRI among
> the assignable device units. Therefore, a response failure on one unit
> might cause I/O failure on other units.
> 
> Remove this response code so that user space can only respond with
> SUCCESS or INVALID. The VMM is recommended to emulate a failure
> response
> as a PRI reset, or PRI disable and changing to a non-PRI domain.
> 
> Fixes: c714f15860fc ("iommufd: Add fault and response message definitions")
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  include/uapi/linux/iommufd.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index ede2b464a761..e31385b75d0b 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -765,14 +765,10 @@ struct iommu_hwpt_pgfault {
>   * @IOMMUFD_PAGE_RESP_INVALID: Could not handle this fault, don't retry
> the
>   *                             access. This is the "Invalid Request" in PCI
>   *                             10.4.2.1.
> - * @IOMMUFD_PAGE_RESP_FAILURE: General error. Drop all subsequent
> faults from
> - *                             this device if possible. This is the "Response
> - *                             Failure" in PCI 10.4.2.1.
>   */
>  enum iommufd_page_response_code {
>  	IOMMUFD_PAGE_RESP_SUCCESS = 0,
>  	IOMMUFD_PAGE_RESP_INVALID,
> -	IOMMUFD_PAGE_RESP_FAILURE,
>  };
> 

It's probably good to add some words here for why FAILURE is
not allowed.

Reviewed-by: Kevin Tian <kevin.tian@...el.com>