/* Set up p2m_top to point to the domain-builder provided p2m pages */
void __init xen_build_dynamic_phys_to_machine(void)
{
unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
unsigned long pfn;
xen_max_p2m_pfn = max_pfn;
p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_missing);
p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(p2m_mid_missing);
p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_init(p2m_top);
p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_identity);
/*
* The domain builder gives us a pre-constructed p2m array in
* mfn_list for all the pages initially given to us, so we just
* need to graft that into our tree structure.
*/
for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
if (p2m_top[topidx] == p2m_mid_missing) {
unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(mid);
p2m_top[topidx] = mid;
}
/*
* As long as the mfn_list has enough entries to completely
* fill a p2m page, pointing into the array is ok. But if
* not the entries beyond the last pfn will be undefined.
*/
if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
unsigned long p2midx;
p2midx = max_pfn % P2M_PER_PAGE;
for ( ; p2midx < P2M_PER_PAGE; p2midx++)
mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
}
p2m_top[topidx][mididx] = &mfn_list[pfn];
}
m2p_override_init();
}
int arch_domain_create(struct domain *d, unsigned int domcr_flags)
{
int rc;
d->arch.relmem = RELMEM_not_started;
/* Idle domains do not need this setup */
if ( is_idle_domain(d) )
return 0;
if ( (rc = p2m_init(d)) != 0 )
goto fail;
rc = -ENOMEM;
if ( (d->shared_info = alloc_xenheap_pages(0, 0)) == NULL )
goto fail;
/* Default the virtual ID to match the physical */
d->arch.vpidr = boot_cpu_data.midr.bits;
clear_page(d->shared_info);
share_xen_page_with_guest(
virt_to_page(d->shared_info), d, XENSHARE_writable);
if ( (rc = p2m_alloc_table(d)) != 0 )
goto fail;
if ( (rc = gicv_setup(d)) != 0 )
goto fail;
if ( (rc = domain_vgic_init(d)) != 0 )
goto fail;
if ( (rc = domain_vtimer_init(d)) != 0 )
goto fail;
if ( d->domain_id )
d->arch.evtchn_irq = GUEST_EVTCHN_PPI;
else
d->arch.evtchn_irq = platform_dom0_evtchn_ppi();
/*
* Virtual UART is only used by linux early printk and decompress code.
* Only use it for the hardware domain because the linux kernel may not
* support multi-platform.
*/
if ( is_hardware_domain(d) && (rc = domain_vuart_init(d)) )
goto fail;
if ( (rc = iommu_domain_init(d)) != 0 )
goto fail;
return 0;
fail:
d->is_dying = DOMDYING_dead;
arch_domain_destroy(d);
return rc;
}
void __init xen_build_dynamic_phys_to_machine(void)
{
unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
unsigned long pfn;
xen_max_p2m_pfn = max_pfn;
p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_missing);
p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(p2m_mid_missing);
p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_top_init(p2m_top);
p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m_identity);
for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
unsigned mididx = p2m_mid_index(pfn);
if (p2m_top[topidx] == p2m_mid_missing) {
unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_mid_init(mid);
p2m_top[topidx] = mid;
}
if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
unsigned long p2midx;
p2midx = max_pfn % P2M_PER_PAGE;
for ( ; p2midx < P2M_PER_PAGE; p2midx++)
mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
}
p2m_top[topidx][mididx] = &mfn_list[pfn];
}
m2p_override_init();
}
static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary)
{
unsigned topidx, mididx, idx;
unsigned long *p2m;
unsigned long *mid_mfn_p;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
/* Pfff.. No boundary cross-over, lets get out. */
if (!idx && check_boundary)
return false;
WARN(p2m_top[topidx][mididx] == p2m_identity,
"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
topidx, mididx);
/*
* Could be done by xen_build_dynamic_phys_to_machine..
*/
if (p2m_top[topidx][mididx] != p2m_missing)
return false;
/* Boundary cross-over for the edges: */
p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
p2m_init(p2m);
p2m_top[topidx][mididx] = p2m;
/* For save/restore we need to MFN of the P2M saved */
mid_mfn_p = p2m_top_mfn_p[topidx];
WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
"P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
topidx, mididx);
mid_mfn_p[mididx] = virt_to_mfn(p2m);
return true;
}
static bool __init __early_alloc_p2m(unsigned long pfn)
{
unsigned topidx, mididx, idx;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
if (!idx)
return false;
WARN(p2m_top[topidx][mididx] == p2m_identity,
"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
topidx, mididx);
if (p2m_top[topidx][mididx] != p2m_missing)
return false;
if (idx) {
unsigned long *p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
unsigned long *mid_mfn_p;
p2m_init(p2m);
p2m_top[topidx][mididx] = p2m;
mid_mfn_p = p2m_top_mfn_p[topidx];
WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
"P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
topidx, mididx);
mid_mfn_p[mididx] = virt_to_mfn(p2m);
}
return idx != 0;
}
/*
* Fully allocate the p2m structure for a given pfn. We need to check
* that both the top and mid levels are allocated, and make sure the
* parallel mfn tree is kept in sync. We may race with other cpus, so
* the new pages are installed with cmpxchg; if we lose the race then
* simply free the page we allocated and use the one that's there.
*/
static bool alloc_p2m(unsigned long pfn)
{
unsigned topidx;
unsigned long *top_mfn_p, *mid_mfn;
pte_t *ptep, *pte_pg;
unsigned int level;
unsigned long flags;
unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
unsigned long p2m_pfn;
ptep = lookup_address(addr, &level);
BUG_ON(!ptep || level != PG_LEVEL_4K);
pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
/* PMD level is missing, allocate a new one */
ptep = alloc_p2m_pmd(addr, pte_pg);
if (!ptep)
return false;
}
if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
topidx = p2m_top_index(pfn);
top_mfn_p = &p2m_top_mfn[topidx];
mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
if (mid_mfn == p2m_mid_missing_mfn) {
/* Separately check the mid mfn level */
unsigned long missing_mfn;
unsigned long mid_mfn_mfn;
unsigned long old_mfn;
mid_mfn = alloc_p2m_page();
if (!mid_mfn)
return false;
p2m_mid_mfn_init(mid_mfn, p2m_missing);
missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
mid_mfn_mfn = virt_to_mfn(mid_mfn);
old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
if (old_mfn != missing_mfn) {
free_p2m_page(mid_mfn);
mid_mfn = mfn_to_virt(old_mfn);
} else {
p2m_top_mfn_p[topidx] = mid_mfn;
}
}
} else {
mid_mfn = NULL;
}
p2m_pfn = pte_pfn(READ_ONCE(*ptep));
if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
/* p2m leaf page is missing */
unsigned long *p2m;
p2m = alloc_p2m_page();
if (!p2m)
return false;
if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
p2m_init(p2m);
else
p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
spin_lock_irqsave(&p2m_update_lock, flags);
if (pte_pfn(*ptep) == p2m_pfn) {
HYPERVISOR_shared_info->arch.p2m_generation++;
wmb(); /* Tools are synchronizing via p2m_generation. */
set_pte(ptep,
pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
wmb(); /* Tools are synchronizing via p2m_generation. */
HYPERVISOR_shared_info->arch.p2m_generation++;
if (mid_mfn)
mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
p2m = NULL;
}
spin_unlock_irqrestore(&p2m_update_lock, flags);
if (p2m)
free_p2m_page(p2m);
}
/* Expanded the p2m? */
if (pfn > xen_p2m_last_pfn) {
xen_p2m_last_pfn = pfn;
HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
}
return true;
}
static void __init xen_rebuild_p2m_list(unsigned long *p2m)
{
unsigned int i, chunk;
unsigned long pfn;
unsigned long *mfns;
pte_t *ptep;
pmd_t *pmdp;
int type;
p2m_missing = alloc_p2m_page();
p2m_init(p2m_missing);
p2m_identity = alloc_p2m_page();
p2m_init(p2m_identity);
p2m_missing_pte = alloc_p2m_page();
paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
p2m_identity_pte = alloc_p2m_page();
paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
for (i = 0; i < PTRS_PER_PTE; i++) {
set_pte(p2m_missing_pte + i,
pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
set_pte(p2m_identity_pte + i,
pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
}
for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
/*
* Try to map missing/identity PMDs or p2m-pages if possible.
* We have to respect the structure of the mfn_list_list
* which will be built just afterwards.
* Chunk size to test is one p2m page if we are in the middle
* of a mfn_list_list mid page and the complete mid page area
* if we are at index 0 of the mid page. Please note that a
* mid page might cover more than one PMD, e.g. on 32 bit PAE
* kernels.
*/
chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
type = xen_p2m_elem_type(pfn);
i = 0;
if (type != P2M_TYPE_PFN)
for (i = 1; i < chunk; i++)
if (xen_p2m_elem_type(pfn + i) != type)
break;
if (i < chunk)
/* Reset to minimal chunk size. */
chunk = P2M_PER_PAGE;
if (type == P2M_TYPE_PFN || i < chunk) {
/* Use initial p2m page contents. */
#ifdef CONFIG_X86_64
mfns = alloc_p2m_page();
copy_page(mfns, xen_p2m_addr + pfn);
#else
mfns = xen_p2m_addr + pfn;
#endif
ptep = populate_extra_pte((unsigned long)(p2m + pfn));
set_pte(ptep,
pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
continue;
}
if (chunk == P2M_PER_PAGE) {
/* Map complete missing or identity p2m-page. */
mfns = (type == P2M_TYPE_MISSING) ?
p2m_missing : p2m_identity;
ptep = populate_extra_pte((unsigned long)(p2m + pfn));
set_pte(ptep,
pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
continue;
}
/* Complete missing or identity PMD(s) can be mapped. */
ptep = (type == P2M_TYPE_MISSING) ?
p2m_missing_pte : p2m_identity_pte;
for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
pmdp = populate_extra_pmd(
(unsigned long)(p2m + pfn) + i * PMD_SIZE);
set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
}
}
}
int arch_domain_create(struct domain *d, unsigned int domcr_flags,
struct xen_arch_domainconfig *config)
{
int rc;
uint8_t gic_version;
d->arch.relmem = RELMEM_not_started;
/* Idle domains do not need this setup */
if ( is_idle_domain(d) )
return 0;
ASSERT(config != NULL);
if ( (rc = p2m_init(d)) != 0 )
goto fail;
rc = -ENOMEM;
if ( (d->shared_info = alloc_xenheap_pages(0, 0)) == NULL )
goto fail;
/* Default the virtual ID to match the physical */
d->arch.vpidr = boot_cpu_data.midr.bits;
clear_page(d->shared_info);
share_xen_page_with_guest(
virt_to_page(d->shared_info), d, XENSHARE_writable);
if ( (rc = domain_io_init(d)) != 0 )
goto fail;
if ( (rc = p2m_alloc_table(d)) != 0 )
goto fail;
/*
* Currently the vGIC is emulating the same version of the
* hardware GIC. Only the value XEN_DOMCTL_CONFIG_GIC_DEFAULT
* is allowed. The DOMCTL will return the actual version of the
* GIC.
*/
rc = -EOPNOTSUPP;
if ( config->gic_version != XEN_DOMCTL_CONFIG_GIC_DEFAULT )
goto fail;
switch ( gic_hw_version() )
{
case GIC_V3:
gic_version = XEN_DOMCTL_CONFIG_GIC_V3;
break;
case GIC_V2:
gic_version = XEN_DOMCTL_CONFIG_GIC_V2;
break;
default:
BUG();
}
config->gic_version = gic_version;
if ( (rc = gicv_setup(d)) != 0 )
goto fail;
if ( (rc = domain_vgic_init(d)) != 0 )
goto fail;
if ( (rc = domain_vtimer_init(d)) != 0 )
goto fail;
/*
* The hardware domain will get a PPI later in
* arch/arm/domain_build.c depending on the
* interrupt map of the hardware.
*/
if ( !is_hardware_domain(d) )
{
d->arch.evtchn_irq = GUEST_EVTCHN_PPI;
/* At this stage vgic_reserve_virq should never fail */
if ( !vgic_reserve_virq(d, GUEST_EVTCHN_PPI) )
BUG();
}
/*
* Virtual UART is only used by linux early printk and decompress code.
* Only use it for the hardware domain because the linux kernel may not
* support multi-platform.
*/
if ( is_hardware_domain(d) && (rc = domain_vuart_init(d)) )
goto fail;
if ( (rc = iommu_domain_init(d)) != 0 )
goto fail;
return 0;
fail:
d->is_dying = DOMDYING_dead;
arch_domain_destroy(d);
return rc;
}
int arch_domain_create(struct domain *d, unsigned int domcr_flags,
struct xen_arch_domainconfig *config)
{
int rc, count = 0;
BUILD_BUG_ON(GUEST_MAX_VCPUS < MAX_VIRT_CPUS);
d->arch.relmem = RELMEM_not_started;
/* Idle domains do not need this setup */
if ( is_idle_domain(d) )
return 0;
ASSERT(config != NULL);
/* p2m_init relies on some value initialized by the IOMMU subsystem */
if ( (rc = iommu_domain_init(d)) != 0 )
goto fail;
if ( (rc = p2m_init(d)) != 0 )
goto fail;
rc = -ENOMEM;
if ( (d->shared_info = alloc_xenheap_pages(0, 0)) == NULL )
goto fail;
/* Default the virtual ID to match the physical */
d->arch.vpidr = boot_cpu_data.midr.bits;
clear_page(d->shared_info);
share_xen_page_with_guest(
virt_to_page(d->shared_info), d, XENSHARE_writable);
switch ( config->gic_version )
{
case XEN_DOMCTL_CONFIG_GIC_NATIVE:
switch ( gic_hw_version () )
{
case GIC_V2:
config->gic_version = XEN_DOMCTL_CONFIG_GIC_V2;
d->arch.vgic.version = GIC_V2;
break;
case GIC_V3:
config->gic_version = XEN_DOMCTL_CONFIG_GIC_V3;
d->arch.vgic.version = GIC_V3;
break;
default:
BUG();
}
break;
case XEN_DOMCTL_CONFIG_GIC_V2:
d->arch.vgic.version = GIC_V2;
break;
case XEN_DOMCTL_CONFIG_GIC_V3:
d->arch.vgic.version = GIC_V3;
break;
default:
rc = -EOPNOTSUPP;
goto fail;
}
if ( (rc = domain_vgic_register(d, &count)) != 0 )
goto fail;
if ( (rc = domain_io_init(d, count + MAX_IO_HANDLER)) != 0 )
goto fail;
if ( (rc = domain_vgic_init(d, config->nr_spis)) != 0 )
goto fail;
if ( (rc = domain_vtimer_init(d, config)) != 0 )
goto fail;
update_domain_wallclock_time(d);
/*
* The hardware domain will get a PPI later in
* arch/arm/domain_build.c depending on the
* interrupt map of the hardware.
*/
if ( !is_hardware_domain(d) )
{
d->arch.evtchn_irq = GUEST_EVTCHN_PPI;
/* At this stage vgic_reserve_virq should never fail */
if ( !vgic_reserve_virq(d, GUEST_EVTCHN_PPI) )
BUG();
}
/*
* Virtual UART is only used by linux early printk and decompress code.
* Only use it for the hardware domain because the linux kernel may not
* support multi-platform.
*/
if ( is_hardware_domain(d) && (rc = domain_vuart_init(d)) )
goto fail;
return 0;
fail:
d->is_dying = DOMDYING_dead;
arch_domain_destroy(d);
return rc;
}
/*
* Fully allocate the p2m structure for a given pfn. We need to check
* that both the top and mid levels are allocated, and make sure the
* parallel mfn tree is kept in sync. We may race with other cpus, so
* the new pages are installed with cmpxchg; if we lose the race then
* simply free the page we allocated and use the one that's there.
*/
static bool alloc_p2m(unsigned long pfn)
{
unsigned topidx, mididx;
unsigned long ***top_p, **mid;
unsigned long *top_mfn_p, *mid_mfn;
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn);
top_p = &p2m_top[topidx];
mid = *top_p;
if (mid == p2m_mid_missing) {
/* Mid level is missing, allocate a new one */
mid = alloc_p2m_page();
if (!mid)
return false;
p2m_mid_init(mid);
if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
free_p2m_page(mid);
}
top_mfn_p = &p2m_top_mfn[topidx];
mid_mfn = p2m_top_mfn_p[topidx];
BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
if (mid_mfn == p2m_mid_missing_mfn) {
/* Separately check the mid mfn level */
unsigned long missing_mfn;
unsigned long mid_mfn_mfn;
mid_mfn = alloc_p2m_page();
if (!mid_mfn)
return false;
p2m_mid_mfn_init(mid_mfn);
missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
mid_mfn_mfn = virt_to_mfn(mid_mfn);
if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
free_p2m_page(mid_mfn);
else
p2m_top_mfn_p[topidx] = mid_mfn;
}
if (p2m_top[topidx][mididx] == p2m_identity ||
p2m_top[topidx][mididx] == p2m_missing) {
/* p2m leaf page is missing */
unsigned long *p2m;
unsigned long *p2m_orig = p2m_top[topidx][mididx];
p2m = alloc_p2m_page();
if (!p2m)
return false;
p2m_init(p2m);
if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
free_p2m_page(p2m);
else
mid_mfn[mididx] = virt_to_mfn(p2m);
}
return true;
}
/*
* Skim over the P2M tree looking at pages that are either filled with
* INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
* replace the P2M leaf with a p2m_missing or p2m_identity.
* Stick the old page in the new P2M tree location.
*/
bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_mfn)
{
unsigned topidx;
unsigned mididx;
unsigned ident_pfns;
unsigned inv_pfns;
unsigned long *p2m;
unsigned long *mid_mfn_p;
unsigned idx;
unsigned long pfn;
/* We only look when this entails a P2M middle layer */
if (p2m_index(set_pfn))
return false;
for (pfn = 0; pfn <= MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
topidx = p2m_top_index(pfn);
if (!p2m_top[topidx])
continue;
if (p2m_top[topidx] == p2m_mid_missing)
continue;
mididx = p2m_mid_index(pfn);
p2m = p2m_top[topidx][mididx];
if (!p2m)
continue;
if ((p2m == p2m_missing) || (p2m == p2m_identity))
continue;
if ((unsigned long)p2m == INVALID_P2M_ENTRY)
continue;
ident_pfns = 0;
inv_pfns = 0;
for (idx = 0; idx < P2M_PER_PAGE; idx++) {
/* IDENTITY_PFNs are 1:1 */
if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
ident_pfns++;
else if (p2m[idx] == INVALID_P2M_ENTRY)
inv_pfns++;
else
break;
}
if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
goto found;
}
return false;
found:
/* Found one, replace old with p2m_identity or p2m_missing */
p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
/* And the other for save/restore.. */
mid_mfn_p = p2m_top_mfn_p[topidx];
/* NOTE: Even if it is a p2m_identity it should still be point to
* a page filled with INVALID_P2M_ENTRY entries. */
mid_mfn_p[mididx] = virt_to_mfn(p2m_missing);
/* Reset where we want to stick the old page in. */
topidx = p2m_top_index(set_pfn);
mididx = p2m_mid_index(set_pfn);
/* This shouldn't happen */
if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
early_alloc_p2m(set_pfn);
if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
return false;
p2m_init(p2m);
p2m_top[topidx][mididx] = p2m;
mid_mfn_p = p2m_top_mfn_p[topidx];
mid_mfn_p[mididx] = virt_to_mfn(p2m);
return true;
}