linux-kernel - Re: [PATCH v5 2/5] iommu/uapi: Add argsz for user filled data

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Date:   Mon, 20 Jul 2020 18:52:33 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Auger Eric <eric.auger@...hat.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Yi Liu <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Jonathan Corbet <corbet@....net>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v5 2/5] iommu/uapi: Add argsz for user filled data

On Fri, 17 Jul 2020 15:44:23 +0200
Auger Eric <eric.auger@...hat.com> wrote:

> 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@...el.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.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?
not literal "flags" but @cache and @granularity are flags in reality. I
think that is OK. I also updated document to say "flags or equivalent".

> >  	__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
> 

[Jacob Pan]