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Subject: Re: [PATCH v5 2/5] iommu/uapi: Add argsz for user filled data
To:     Jacob Pan <jacob.jun.pan@linux.intel.com>,
        iommu@lists.linux-foundation.org,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        Alex Williamson <alex.williamson@redhat.com>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Yi Liu <yi.l.liu@intel.com>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Christoph Hellwig <hch@infradead.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        Jonathan Corbet <corbet@lwn.net>
References: <1594925117-64892-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1594925117-64892-3-git-send-email-jacob.jun.pan@linux.intel.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <1538ec69-62a2-ea04-0870-a583fc63a2bf@redhat.com>
Date:   Fri, 17 Jul 2020 15:44:23 +0200
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Hi Jacob,

On 7/16/20 8:45 PM, Jacob Pan wrote:
> As IOMMU UAPI gets extended, user data size may increase. To support
> backward compatibiliy, this patch introduces a size field to each UAPI
> data structures. It is *always* the responsibility for the user to fill in
> the correct size. Padding fields are adjusted to ensure 8 byte alignment.
> 
> Specific scenarios for user data handling are documented in:
> Documentation/userspace-api/iommu.rst
> 
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>  include/uapi/linux/iommu.h | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> index e907b7091a46..d5e9014f690e 100644
> --- a/include/uapi/linux/iommu.h
> +++ b/include/uapi/linux/iommu.h
> @@ -135,6 +135,7 @@ enum iommu_page_response_code {
>  
>  /**
>   * struct iommu_page_response - Generic page response information
> + * @argsz: User filled size of this data
>   * @version: API version of this structure
>   * @flags: encodes whether the corresponding fields are valid
>   *         (IOMMU_FAULT_PAGE_RESPONSE_* values)
> @@ -143,6 +144,7 @@ enum iommu_page_response_code {
>   * @code: response code from &enum iommu_page_response_code
>   */
>  struct iommu_page_response {
> +	__u32	argsz;
>  #define IOMMU_PAGE_RESP_VERSION_1	1
Don't you need to incr the version for all the modified structs?
>  	__u32	version;
>  #define IOMMU_PAGE_RESP_PASID_VALID	(1 << 0)
> @@ -218,6 +220,7 @@ struct iommu_inv_pasid_info {
>  /**
>   * struct iommu_cache_invalidate_info - First level/stage invalidation
>   *     information
> + * @argsz: User filled size of this data
>   * @version: API version of this structure
>   * @cache: bitfield that allows to select which caches to invalidate
>   * @granularity: defines the lowest granularity used for the invalidation:
> @@ -246,6 +249,7 @@ struct iommu_inv_pasid_info {
>   * must support the used granularity.
>   */
>  struct iommu_cache_invalidate_info {
> +	__u32	argsz;
>  #define IOMMU_CACHE_INVALIDATE_INFO_VERSION_1 1
>  	__u32	version;
so there is no "flags" field in this struct. Is it OK?
>  /* IOMMU paging structure cache */
> @@ -255,7 +259,7 @@ struct iommu_cache_invalidate_info {
>  #define IOMMU_CACHE_INV_TYPE_NR		(3)
>  	__u8	cache;
>  	__u8	granularity;
> -	__u8	padding[2];
> +	__u8	padding[6];
>  	union {
>  		struct iommu_inv_pasid_info pasid_info;
>  		struct iommu_inv_addr_info addr_info;
> @@ -292,6 +296,7 @@ struct iommu_gpasid_bind_data_vtd {
>  
>  /**
>   * struct iommu_gpasid_bind_data - Information about device and guest PASID binding
> + * @argsz:	User filled size of this data
>   * @version:	Version of this data structure
>   * @format:	PASID table entry format
>   * @flags:	Additional information on guest bind request
> @@ -309,17 +314,18 @@ struct iommu_gpasid_bind_data_vtd {
>   * PASID to host PASID based on this bind data.
>   */
>  struct iommu_gpasid_bind_data {
> +	__u32 argsz;
>  #define IOMMU_GPASID_BIND_VERSION_1	1
>  	__u32 version;
>  #define IOMMU_PASID_FORMAT_INTEL_VTD	1
>  	__u32 format;
> +	__u32 addr_width;
>  #define IOMMU_SVA_GPASID_VAL	(1 << 0) /* guest PASID valid */
>  	__u64 flags;
>  	__u64 gpgd;
>  	__u64 hpasid;
>  	__u64 gpasid;
> -	__u32 addr_width;
> -	__u8  padding[12];
> +	__u8  padding[8];
>  	/* Vendor specific data */
>  	union {
>  		struct iommu_gpasid_bind_data_vtd vtd;
> 
Thanks

Eric