[Xen-devel] [hybrid]: code review for function mapping pfn to foreign mfn

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

Hi,

I wrote up some code to map/unmap pfn to mfn for hybrid. I wonder if anyone
can please look at it and give any comments. I tested it and seems to work
ok.

Basically, the library, xl running in hybrid dom0, needs to map domU pages
during guest creation. I tried using existing add to physmap, mmu_update,
but nothing was feasible. So wrote this. Its called from
privcmd_ioctl_mmap_batch().

thanks,
Mukesh


/* add frames from foreign domain to current domain physmap. Similar to 
 * XENMEM_add_to_physmap but the mfn frame is foreign, is being mapped into 
 * current privileged domain, and is not removed from foreign domain. 
 * Usage: libxl when creating guest in hybrid dom0 doing privcmd_ioctl_mmap
 * Return: 0 success
 */
static long _add_foreign_to_pmap_batch(XEN_GUEST_HANDLE(void) arg)
{
    struct xen_add_to_foreign_pmap_batch pmapb;
    unsigned long rc=0, i, prev_mfn, mfn = 0;
    struct domain *fdom, *currd = current->domain;
    p2m_type_t p2mt;

    if ( copy_from_guest(&pmapb, arg, 1) )
        return -EFAULT;

    fdom = get_pg_owner(pmapb.foreign_domid);

    if ( fdom== NULL ) {
        put_pg_owner(fdom);
        return -EPERM;
    }

    for (i=0; (rc == 0) && (i < pmapb.count); i++) {
        unsigned long fgmfn = pmapb.gmfn+i, gpfn = pmapb.gpfn+i;
        mfn = mfn_x(gfn_to_mfn_query(p2m_get_hostp2m(fdom), fgmfn, &p2mt));
        if ( !p2m_is_valid(p2mt) )
            rc = -EINVAL;

        if ( !rc && !get_page_from_pagenr(mfn, fdom) )
            rc = -EPERM;

        if (!rc) 
            put_page(mfn_to_page(mfn));
        else 
            break;

        /* Remove previously mapped page if it was present. */
        prev_mfn = gmfn_to_mfn(currd, gpfn);
        if ( mfn_valid(prev_mfn) )
        {
            if ( is_xen_heap_mfn(prev_mfn) )
                /* Xen heap frames are simply unhooked from this phys slot */
                guest_physmap_remove_page(currd, gpfn, prev_mfn, 0);
            else
                /* Normal domain memory is freed, to avoid leaking memory. */
                guest_remove_page(currd, gpfn);
        }
        /* Map at new location. */
        /* Can't use guest_physmap_add_page() because it will update the m2p
         * table so mfn ---> gpfn in dom0 and not gpfn of domU.
         */
        /* rc = guest_physmap_add_page(currd, gpfn, mfn, 0); */

        rc = set_mmio_p2m_entry(p2m_get_hostp2m(currd), gpfn, mfn);
        if (rc==0) {
            printk("guest_physmap_add_page failed.gpfn:%lx mfn:%lx fgmfn:%lx\n",
                   gpfn, mfn, fgmfn);
            rc == -EINVAL;
        } else 
            rc = 0;
    }

    pmapb.count = i;
    copy_to_guest(arg, &pmapb, 1);
    put_pg_owner(fdom);
    return rc;
}

static long noinline _rem_foreign_pmap_batch(XEN_GUEST_HANDLE(void) arg)
{
    xen_pfn_t gmfn;
    struct xen_rem_foreign_pmap_batch pmapb;
    p2m_type_t p2mt;
    int i, rc=0;
    struct domain *currd = current->domain;

    if ( copy_from_guest(&pmapb, arg, 1) )
        return -EFAULT;

    for ( gmfn=pmapb.s_gpfn, i=0;  i < pmapb.count;  i++, gmfn++ ) {

        mfn_t mfn = mfn_x(gfn_to_mfn(p2m_get_hostp2m(currd), gmfn, &p2mt));
        if ( unlikely(!mfn_valid(mfn)) )
        {
            gdprintk(XENLOG_INFO, "%s: Domain:%u gmfn:%lx invalid\n",
                     __FUNCTION__, currd->domain_id, gmfn);
            rc = -EINVAL;
            break;
        }
        /* guest_physmap_remove_page(currd, gmfn, mfn, 0); */
        clear_mmio_p2m_entry(p2m_get_hostp2m(currd), gmfn);
    }
    pmapb.count = i;
    copy_to_guest(arg, &pmapb, 1);
    return rc;
}


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