Re: [Xen-devel] [PATCH v21 1/2] common: add a new mappable resource type: XENMEM_resource_grant_table

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.08.18 at 12:38, <Paul.Durrant@xxxxxxxxxx> wrote:
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 08 August 2018 11:30
>> 
>> >>> On 08.08.18 at 11:00, <paul.durrant@xxxxxxxxxx> wrote:
>> > @@ -3860,6 +3866,47 @@ int mem_sharing_gref_to_gfn(struct
>> grant_table *gt, grant_ref_t ref,
>> >  }
>> >  #endif
>> >
>> > +/* caller must hold write lock */
>> > +static int gnttab_get_status_frame_mfn(struct domain *d,
>> > +                                       unsigned long idx, mfn_t *mfn)
>> > +{
>> > +    struct grant_table *gt = d->grant_table;
>> 
>> const?
>> 
> 
> IIRC that didn't work because gnttab_grow_table() modifies the content.

But you don't pass gt to the function:

>> > +    ASSERT(gt->gt_version == 2);
>> > +
>> > +    if ( idx >= nr_status_frames(gt) )
>> > +    {
>> > +        unsigned long nr = status_to_grant_frames(idx + 1);
>> > +
>> > +        if ( nr <= gt->max_grant_frames )
>> > +            gnttab_grow_table(d, nr);

^^^

>> > @@ -3906,6 +3943,38 @@ int gnttab_map_frame(struct domain *d,
>> unsigned long idx, gfn_t gfn,
>> >      return rc;
>> >  }
>> >
>> > +int gnttab_get_shared_frame(struct domain *d, unsigned long idx,
>> > +                            mfn_t *mfn)
>> > +{
>> > +    struct grant_table *gt = d->grant_table;
>> > +    int rc;
>> > +
>> > +    grant_write_lock(gt);
>> > +
>> > +    if ( gt->gt_version == 0 )
>> > +        gt->gt_version = 1;
>> 
>> Since you've moved this here instead of dropping it, what requirement
>> have you found for this to be set (other than the ASSERT() you put in
>> gnttab_get_shared_frame_mfn()?
>> 
> 
> The code in patch #2 is executed before the grant table version is set. I 
> could alternatively have libxl explicitly set the version to 1 before trying 
> to seed the table.

But that's not my point. What's wrong with leaving it at zero?

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel