Re: [Xen-devel] [PATCH 3/3] xen/privcmd: add PRIVCMD_MMAPBATCH_V2 ioctl

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-08-24 at 12:41 +0100, Konrad Rzeszutek Wilk wrote:
> > >> +struct privcmd_mmapbatch_v2 {
> > >> +        unsigned int num; /* number of pages to populate */
> > > 
> > > unsigend int? Not 'u32'?
> > >> +        domid_t dom;      /* target domain */
> > >> +        __u64 addr;       /* virtual address */
> > >> +        const xen_pfn_t __user *arr; /* array of mfns */
> > >> +        int __user *err;  /* array of error codes */
> > > 
> > > int? Not a specific type?
> > 
> > It's an existing interface supported by classic Xen kernels and
> > currently being used by libxc.  So while I agree that it's not the best
> > interface, I don't think it can be changed.
> 
> How does it work with a 64-bit dom0 and 32-bit userspace? Is the libxc
> smart enough to figure out the size of the structure?

This already doesn't work for numerous reasons.

The man one being that libxc will make 32 bit hypercalls, but when the
kernel forwards them on they look like 64 bit ones.

Ian.



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