Re: [Xen-devel] [PATCH v2] libxc: add xc_domain_add_to_physmap_batch to wrap XENMEM_add_to_physmap_batch

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jun 21, 2017 at 01:29:26AM +0800, Zhongze Liu wrote:
> This is a preparation for the proposal "allow setting up shared memory areas
> between VMs from xl config file". See:
> V2: https://lists.xen.org/archives/html/xen-devel/2017-06/msg02256.html
> V1: https://lists.xen.org/archives/html/xen-devel/2017-05/msg01288.html
> 
> The plan is to use XENMEM_add_to_physmap_batch in xl to map foregin pages from
> one DomU to another so that the page could be shared. But currently there is 
> no
> wrapper for XENMEM_add_to_physmap_batch in libxc, so we just add a wrapper for
> it.
> 
> Signed-off-by: Zhongze Liu <blackskygg@xxxxxxxxx>
> ---
> +int xc_domain_add_to_physmap_batch(xc_interface *xch,
> +                                   domid_t domid,
> +                                   domid_t foreign_domid,
> +                                   unsigned int space,
> +                                   unsigned int size,
> +                                   xen_ulong_t *idxs,
> +                                   xen_pfn_t *gpfns,
> +                                   int *errs)
> +{
> +    int rc;
> +    DECLARE_HYPERCALL_BOUNCE(idxs, size * sizeof(*idxs), 
> XC_HYPERCALL_BUFFER_BOUNCE_IN);
> +    DECLARE_HYPERCALL_BOUNCE(gpfns, size * sizeof(*gpfns), 
> XC_HYPERCALL_BUFFER_BOUNCE_IN);
> +    DECLARE_HYPERCALL_BOUNCE(errs, size * sizeof(*errs), 
> XC_HYPERCALL_BUFFER_BOUNCE_OUT);
> +
> +    struct xen_add_to_physmap_batch xatp_batch = {
> +        .domid = domid,
> +        .space = space,
> +        .size = size,
> +        .u = {.foreign_domid = foreign_domid}

Coding style issue.

Just a note, the struct is different for pre-4.7 and post-4.7 Xen. You
don't need to implement a version of this function for pre-4.7 Xen.

> +    };
> +
> +    if ( xc_hypercall_bounce_pre(xch, idxs)  ||
> +         xc_hypercall_bounce_pre(xch, gpfns) ||
> +         xc_hypercall_bounce_pre(xch, errs)  )
> +    {
> +        PERROR("Could not bounce memory for XENMEM_add_to_physmap_batch");
> +        goto out;

rc will be uninitialised in this exit path.

> +    }
> +
> +    set_xen_guest_handle(xatp_batch.idxs, idxs);
> +    set_xen_guest_handle(xatp_batch.gpfns, gpfns);
> +    set_xen_guest_handle(xatp_batch.errs, errs);
> +
> +    rc = do_memory_op(xch, XENMEM_add_to_physmap_batch,
> +                      &xatp_batch, sizeof(xatp_batch));
> +
> +out:
> +    xc_hypercall_bounce_post(xch, idxs);
> +    xc_hypercall_bounce_post(xch, gpfns);
> +    xc_hypercall_bounce_post(xch, errs);
> +
> +    return rc;
> +}
> +
>  int xc_domain_claim_pages(xc_interface *xch,
>                                 uint32_t domid,
>                                 unsigned long nr_pages)
> -- 
> 2.13.1
> 

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