[PATCH RFC] Remove PV superpage support (v1).

[PATCH RFC] Remove PV superpage support (v1).

[Konrad Rzeszutek Wilk]

Hey,

This patchset removes the opt_allow_superpage parameter and also the code around it.
I've tested (migration, bootup, etc) with normal PV and HVM guests and all works.

I haven't yet tested kernels that had PV superpage support in (UEK2, UEK3, classic
Xen kernels) but looking at the code it ought to just print in the dmesg:

"Xen hypervisor is not configured to allow hugepages"

and fail when setting up hugepages. That will be tested shortly (hence
the RFC nature).

I am hoping the maintainers can guide me in how they would like:
 - Deal with documentation? I removed the allowsuperpage from documentation
   but perhaps it should just mention deprecated?
 - I left put_superpage as put_page_from_l2e calls it - but I can't see
   how the _PAGE_PSE bit would be set as you won't be able to even
   put that bit on (after my patch). Perhaps just make it an
   ASSERT in put_page_from_l2e?
 - With the removal of this some of the code could be made simpler:
   if (.. _PAGE_PSE  return -EINVAL;
   instead of inverse: if (! .._PAGE_PSE) ..
   I can make that an follow up patch if desired?


 docs/misc/xen-command-line.markdown |   7 --
 tools/libxc/include/xenguest.h      |   3 +-
 tools/libxc/xc_nomigrate.c          |   2 +-
 tools/libxc/xc_sr_restore.c         |   6 +-
 tools/libxl/libxl_internal.h        |   2 +-
 tools/libxl/libxl_save_callout.c    |   4 +-
 tools/libxl/libxl_save_helper.c     |   3 +-
 tools/libxl/libxl_stream_read.c     |   2 +-
 xen/arch/x86/domain.c               |   2 -
 xen/arch/x86/domain_build.c         |   2 -
 xen/arch/x86/mm.c                   | 241 ++----------------------------------
 xen/include/asm-x86/config.h        |   9 +-
 xen/include/asm-x86/guest_pt.h      |   4 +-
 xen/include/asm-x86/mm.h            |  19 ---
 xen/include/public/xen.h            |   4 +-
 15 files changed, 23 insertions(+), 287 deletions(-)

Konrad Rzeszutek Wilk (1):
      xen/libxl/libxl: RIP PV superpage.

[PATCH RFC] xen/libxl/libxl: RIP PV superpage.

[Konrad Rzeszutek Wilk]

The last bastion of users is moving away from needing
this.

Please note that there was an partial removal by
c/s 9b3c6b13e0c085ceb53210f8e682a073096b94fa
"libxc: remove superpages option for pv domains" so an user
could not even run PV guests with superpage.

HVM guests are not affected - they have been able to use
superpages (called hugepages) if the CPU supports 2MB or 1GB
since Xen 3.3.

This is reported in the ring buffer:
(XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB

AMD CPUs that support 2MB require NPT aka Rapid Virtualization
Indexing. This was introduced in third generation Opteron -
Barcelona.

Intel CPUs that support 2MB require EPT aka Extended Page Tables.
This was introduced in Westmere microarchitecture.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 docs/misc/xen-command-line.markdown |   7 --
 tools/libxc/include/xenguest.h      |   3 +-
 tools/libxc/xc_nomigrate.c          |   2 +-
 tools/libxc/xc_sr_restore.c         |   6 +-
 tools/libxl/libxl_internal.h        |   2 +-
 tools/libxl/libxl_save_callout.c    |   4 +-
 tools/libxl/libxl_save_helper.c     |   3 +-
 tools/libxl/libxl_stream_read.c     |   2 +-
 xen/arch/x86/domain.c               |   2 -
 xen/arch/x86/domain_build.c         |   2 -
 xen/arch/x86/mm.c                   | 241 ++----------------------------------
 xen/include/asm-x86/config.h        |   9 +-
 xen/include/asm-x86/guest_pt.h      |   4 +-
 xen/include/asm-x86/mm.h            |  19 ---
 xen/include/public/xen.h            |   4 +-
 15 files changed, 23 insertions(+), 287 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index d267a04..6ea89b0 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -133,13 +133,6 @@ resume.
 `s3_mode` instructs Xen to set up the boot time (option `vga=`) video
 mode during S3 resume.
 
-### allowsuperpage
-> `= <boolean>`
-
-> Default: `true`
-
-Permit Xen to use superpages when performing memory management.
-
 ### altp2m (Intel)
 > `= <boolean>`
 
diff --git a/tools/libxc/include/xenguest.h b/tools/libxc/include/xenguest.h
index d48b3ff..11ea79b 100644
--- a/tools/libxc/include/xenguest.h
+++ b/tools/libxc/include/xenguest.h
@@ -113,7 +113,6 @@ struct restore_callbacks {
  * @parm store_mfn returned with the mfn of the store page
  * @parm hvm non-zero if this is a HVM restore
  * @parm pae non-zero if this HVM domain has PAE support enabled
- * @parm superpages non-zero to allocate guest memory with superpages
  * @parm checkpointed_stream non-zero if the far end of the stream is using checkpointing
  * @parm callbacks non-NULL to receive a callback to restore toolstack
  *       specific data
@@ -123,7 +122,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                       unsigned int store_evtchn, unsigned long *store_mfn,
                       domid_t store_domid, unsigned int console_evtchn,
                       unsigned long *console_mfn, domid_t console_domid,
-                      unsigned int hvm, unsigned int pae, int superpages,
+                      unsigned int hvm, unsigned int pae,
                       int checkpointed_stream,
                       struct restore_callbacks *callbacks);
 
diff --git a/tools/libxc/xc_nomigrate.c b/tools/libxc/xc_nomigrate.c
index 902429e..1bb4477 100644
--- a/tools/libxc/xc_nomigrate.c
+++ b/tools/libxc/xc_nomigrate.c
@@ -32,7 +32,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                       unsigned int store_evtchn, unsigned long *store_mfn,
                       domid_t store_domid, unsigned int console_evtchn,
                       unsigned long *console_mfn, domid_t console_domid,
-                      unsigned int hvm, unsigned int pae, int superpages,
+                      unsigned int hvm, unsigned int pae,
                       int checkpointed_stream,
                       struct restore_callbacks *callbacks)
 {
diff --git a/tools/libxc/xc_sr_restore.c b/tools/libxc/xc_sr_restore.c
index d4d33fd..c8b7d1f 100644
--- a/tools/libxc/xc_sr_restore.c
+++ b/tools/libxc/xc_sr_restore.c
@@ -724,7 +724,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                       unsigned int store_evtchn, unsigned long *store_mfn,
                       domid_t store_domid, unsigned int console_evtchn,
                       unsigned long *console_gfn, domid_t console_domid,
-                      unsigned int hvm, unsigned int pae, int superpages,
+                      unsigned int hvm, unsigned int pae,
                       int checkpointed_stream,
                       struct restore_callbacks *callbacks)
 {
@@ -746,9 +746,9 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
     if ( checkpointed_stream )
         assert(callbacks->checkpoint);
 
-    DPRINTF("fd %d, dom %u, hvm %u, pae %u, superpages %d"
+    DPRINTF("fd %d, dom %u, hvm %u, pae %u"
             ", checkpointed_stream %d", io_fd, dom, hvm, pae,
-            superpages, checkpointed_stream);
+            checkpointed_stream);
 
     if ( xc_domain_getinfo(xch, dom, 1, &ctx.dominfo) != 1 )
     {
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index b194e65..a6d167d 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3478,7 +3478,7 @@ _hidden int libxl__restore_emulator_xenstore_data
 _hidden void libxl__xc_domain_restore(libxl__egc *egc,
                                       libxl__domain_create_state *dcs,
                                       libxl__save_helper_state *shs,
-                                      int hvm, int pae, int superpages);
+                                      int hvm, int pae);
 /* If rc==0 then retval is the return value from xc_domain_save
  * and errnoval is the errno value it provided.
  * If rc!=0, retval and errnoval are undefined. */
diff --git a/tools/libxl/libxl_save_callout.c b/tools/libxl/libxl_save_callout.c
index 45b9727..0b60422 100644
--- a/tools/libxl/libxl_save_callout.c
+++ b/tools/libxl/libxl_save_callout.c
@@ -43,7 +43,7 @@ static void helper_done(libxl__egc *egc, libxl__save_helper_state *shs);
 
 void libxl__xc_domain_restore(libxl__egc *egc, libxl__domain_create_state *dcs,
                               libxl__save_helper_state *shs,
-                              int hvm, int pae, int superpages)
+                              int hvm, int pae)
 {
     STATE_AO_GC(dcs->ao);
 
@@ -60,7 +60,7 @@ void libxl__xc_domain_restore(libxl__egc *egc, libxl__domain_create_state *dcs,
         state->store_port,
         state->store_domid, state->console_port,
         state->console_domid,
-        hvm, pae, superpages,
+        hvm, pae,
         cbflags, dcs->restore_params.checkpointed_stream,
     };
 
diff --git a/tools/libxl/libxl_save_helper.c b/tools/libxl/libxl_save_helper.c
index 39038f9..d1bb5b9 100644
--- a/tools/libxl/libxl_save_helper.c
+++ b/tools/libxl/libxl_save_helper.c
@@ -274,7 +274,6 @@ int main(int argc, char **argv)
         domid_t console_domid =    strtoul(NEXTARG,0,10);
         unsigned int hvm =         strtoul(NEXTARG,0,10);
         unsigned int pae =         strtoul(NEXTARG,0,10);
-        int superpages =           strtoul(NEXTARG,0,10);
         unsigned cbflags =         strtoul(NEXTARG,0,10);
         int checkpointed =         strtoul(NEXTARG,0,10);
         assert(!*++argv);
@@ -289,7 +288,7 @@ int main(int argc, char **argv)
 
         r = xc_domain_restore(xch, io_fd, dom, store_evtchn, &store_mfn,
                               store_domid, console_evtchn, &console_mfn,
-                              console_domid, hvm, pae, superpages,
+                              console_domid, hvm, pae,
                               checkpointed,
                               &helper_restore_callbacks);
         helper_stub_restore_results(store_mfn,console_mfn,0);
diff --git a/tools/libxl/libxl_stream_read.c b/tools/libxl/libxl_stream_read.c
index dac134e..3be8b91 100644
--- a/tools/libxl/libxl_stream_read.c
+++ b/tools/libxl/libxl_stream_read.c
@@ -549,7 +549,7 @@ static bool process_record(libxl__egc *egc,
         break;
 
     case REC_TYPE_LIBXC_CONTEXT:
-        libxl__xc_domain_restore(egc, dcs, &stream->shs, 0, 0, 0);
+        libxl__xc_domain_restore(egc, dcs, &stream->shs, 0, 0);
         break;
 
     case REC_TYPE_EMULATOR_XENSTORE_DATA:
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 352c194..5f800f6 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2327,8 +2327,6 @@ static int relinquish_memory(
             BUG();
         }
 
-        clear_superpage_mark(page);
-
         if ( test_and_clear_bit(_PGC_allocated, &page->count_info) )
             put_page(page);
 
diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
index cb287f0..7ee1227 100644
--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -828,8 +828,6 @@ static __init void setup_pv_physmap(struct domain *d, unsigned long pgtbl_pfn,
                                              0)) != NULL )
             {
                 *pl2e = l2e_from_page(page, L1_PROT|_PAGE_DIRTY|_PAGE_PSE);
-                if ( opt_allow_superpage )
-                    get_superpage(page_to_mfn(page), d);
                 vphysmap_start += 1UL << L2_PAGETABLE_SHIFT;
                 continue;
             }
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 1ee431e..5a529f2 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -152,18 +152,13 @@ struct rangeset *__read_mostly mmio_ro_ranges;
 
 #define PAGE_CACHE_ATTRS (_PAGE_PAT|_PAGE_PCD|_PAGE_PWT)
 
-bool_t __read_mostly opt_allow_superpage;
-boolean_param("allowsuperpage", opt_allow_superpage);
-
 static void put_superpage(unsigned long mfn);
 
 static uint32_t base_disallow_mask;
 /* Global bit is allowed to be set on L1 PTEs. Intended for user mappings. */
 #define L1_DISALLOW_MASK ((base_disallow_mask | _PAGE_GNTTAB) & ~_PAGE_GLOBAL)
 
-#define L2_DISALLOW_MASK (unlikely(opt_allow_superpage) \
-                          ? base_disallow_mask & ~_PAGE_PSE \
-                          : base_disallow_mask)
+#define L2_DISALLOW_MASK (base_disallow_mask)
 
 #define l3_disallow_mask(d) (!is_pv_32bit_domain(d) ? \
                              base_disallow_mask : 0xFFFFF198U)
@@ -209,15 +204,6 @@ static void __init init_frametable_chunk(void *start, void *end)
     memset(end, -1, s - e);
 }
 
-static void __init init_spagetable(void)
-{
-    BUILD_BUG_ON(XEN_VIRT_END > SPAGETABLE_VIRT_START);
-
-    init_frametable_chunk(spage_table,
-                          mem_hotplug ? spage_table + SPAGETABLE_NR
-                                      : pdx_to_spage(max_pdx - 1) + 1);
-}
-
 void __init init_frametable(void)
 {
     unsigned int sidx, eidx, nidx;
@@ -242,9 +228,6 @@ void __init init_frametable(void)
                          : end_pg;
     init_frametable_chunk(pdx_to_page(sidx * PDX_GROUP_COUNT), top_pg);
     memset(end_pg, -1, (unsigned long)top_pg - (unsigned long)end_pg);
-
-    if (opt_allow_superpage)
-        init_spagetable();
 }
 
 #ifndef NDEBUG
@@ -985,20 +968,7 @@ get_page_from_l2e(
         return rc;
     }
 
-    if ( !opt_allow_superpage )
-    {
-        MEM_LOG("Attempt to map superpage without allowsuperpage "
-                "flag in hypervisor");
-        return -EINVAL;
-    }
-
-    if ( mfn & (L1_PAGETABLE_ENTRIES-1) )
-    {
-        MEM_LOG("Unaligned superpage map attempt mfn %lx", mfn);
-        return -EINVAL;
-    }
-
-    return get_superpage(mfn, d);
+    return -EINVAL;
 }
 
 
@@ -1853,10 +1823,7 @@ static int mod_l2_entry(l2_pgentry_t *pl2e,
         }
 
         /* Fast path for identical mapping and presence. */
-        if ( !l2e_has_changed(ol2e, nl2e,
-                              unlikely(opt_allow_superpage)
-                              ? _PAGE_PSE | _PAGE_RW | _PAGE_PRESENT
-                              : _PAGE_PRESENT) )
+        if ( !l2e_has_changed(ol2e, nl2e, _PAGE_PRESENT) )
         {
             adjust_guest_l2e(nl2e, d);
             if ( UPDATE_ENTRY(l2, pl2e, ol2e, nl2e, pfn, vcpu, preserve_ad) )
@@ -2511,22 +2478,6 @@ int get_page_type_preemptible(struct page_info *page, unsigned long type)
     return __get_page_type(page, type, 1);
 }
 
-static int get_spage_pages(struct page_info *page, struct domain *d)
-{
-    int i;
-
-    for (i = 0; i < (1<<PAGETABLE_ORDER); i++, page++)
-    {
-        if (!get_page_and_type(page, d, PGT_writable_page))
-        {
-            while (--i >= 0)
-                put_page_and_type(--page);
-            return 0;
-        }
-    }
-    return 1;
-}
-
 static void put_spage_pages(struct page_info *page)
 {
     int i;
@@ -2538,167 +2489,10 @@ static void put_spage_pages(struct page_info *page)
     return;
 }
 
-static int mark_superpage(struct spage_info *spage, struct domain *d)
-{
-    unsigned long x, nx, y = spage->type_info;
-    int pages_done = 0;
-
-    ASSERT(opt_allow_superpage);
-
-    do {
-        x = y;
-        nx = x + 1;
-        if ( (x & SGT_type_mask) == SGT_mark )
-        {
-            MEM_LOG("Duplicate superpage mark attempt mfn %lx",
-                    spage_to_mfn(spage));
-            if ( pages_done )
-                put_spage_pages(spage_to_page(spage));
-            return -EINVAL;
-        }
-        if ( (x & SGT_type_mask) == SGT_dynamic )
-        {
-            if ( pages_done )
-            {
-                put_spage_pages(spage_to_page(spage));
-                pages_done = 0;
-            }
-        }
-        else if ( !pages_done )
-        {
-            if ( !get_spage_pages(spage_to_page(spage), d) )
-            {
-                MEM_LOG("Superpage type conflict in mark attempt mfn %lx",
-                        spage_to_mfn(spage));
-                return -EINVAL;
-            }
-            pages_done = 1;
-        }
-        nx = (nx & ~SGT_type_mask) | SGT_mark;
-
-    } while ( (y = cmpxchg(&spage->type_info, x, nx)) != x );
-
-    return 0;
-}
-
-static int unmark_superpage(struct spage_info *spage)
-{
-    unsigned long x, nx, y = spage->type_info;
-    unsigned long do_pages = 0;
-
-    ASSERT(opt_allow_superpage);
-
-    do {
-        x = y;
-        nx = x - 1;
-        if ( (x & SGT_type_mask) != SGT_mark )
-        {
-            MEM_LOG("Attempt to unmark unmarked superpage mfn %lx",
-                    spage_to_mfn(spage));
-            return -EINVAL;
-        }
-        if ( (nx & SGT_count_mask) == 0 )
-        {
-            nx = (nx & ~SGT_type_mask) | SGT_none;
-            do_pages = 1;
-        }
-        else
-        {
-            nx = (nx & ~SGT_type_mask) | SGT_dynamic;
-        }
-    } while ( (y = cmpxchg(&spage->type_info, x, nx)) != x );
-
-    if ( do_pages )
-        put_spage_pages(spage_to_page(spage));
-
-    return 0;
-}
-
-void clear_superpage_mark(struct page_info *page)
-{
-    struct spage_info *spage;
-
-    if ( !opt_allow_superpage )
-        return;
-
-    spage = page_to_spage(page);
-    if ((spage->type_info & SGT_type_mask) == SGT_mark)
-        unmark_superpage(spage);
-
-}
-
-int get_superpage(unsigned long mfn, struct domain *d)
-{
-    struct spage_info *spage;
-    unsigned long x, nx, y;
-    int pages_done = 0;
-
-    ASSERT(opt_allow_superpage);
-
-    if ( !mfn_valid(mfn | (L1_PAGETABLE_ENTRIES - 1)) )
-        return -EINVAL;
-
-    spage = mfn_to_spage(mfn);
-    y = spage->type_info;
-    do {
-        x = y;
-        nx = x + 1;
-        if ( (x & SGT_type_mask) != SGT_none )
-        {
-            if ( pages_done )
-            {
-                put_spage_pages(spage_to_page(spage));
-                pages_done = 0;
-            }
-        }
-        else
-        {
-            if ( !get_spage_pages(spage_to_page(spage), d) )
-            {
-                MEM_LOG("Type conflict on superpage mapping mfn %lx",
-                        spage_to_mfn(spage));
-                return -EINVAL;
-            }
-            pages_done = 1;
-            nx = (nx & ~SGT_type_mask) | SGT_dynamic;
-        }
-    } while ( (y = cmpxchg(&spage->type_info, x, nx)) != x );
-
-    return 0;
-}
-
 static void put_superpage(unsigned long mfn)
 {
-    struct spage_info *spage;
-    unsigned long x, nx, y;
-    unsigned long do_pages = 0;
-
-    if ( !opt_allow_superpage )
-    {
-        put_spage_pages(mfn_to_page(mfn));
-        return;
-    }
-
-    spage = mfn_to_spage(mfn);
-    y = spage->type_info;
-    do {
-        x = y;
-        nx = x - 1;
-        if ((x & SGT_type_mask) == SGT_dynamic)
-        {
-            if ((nx & SGT_count_mask) == 0)
-            {
-                nx = (nx & ~SGT_type_mask) | SGT_none;
-                do_pages = 1;
-            }
-        }
-
-    } while ((y = cmpxchg(&spage->type_info, x, nx)) != x);
-
-    if (do_pages)
-        put_spage_pages(spage_to_page(spage));
-
-    return;
+    ASSERT(1); /* This should really not be called. */
+    put_spage_pages(mfn_to_page(mfn));
 }
 
 int put_old_guest_table(struct vcpu *v)
@@ -3437,29 +3231,8 @@ long do_mmuext_op(
 
         case MMUEXT_MARK_SUPER:
         case MMUEXT_UNMARK_SUPER:
-        {
-            unsigned long mfn = op.arg1.mfn;
-
-            if ( !opt_allow_superpage )
-            {
-                MEM_LOG("Superpages disallowed");
-                rc = -ENOSYS;
-            }
-            else if ( unlikely(d != pg_owner) )
-                rc = -EPERM;
-            else if ( mfn & (L1_PAGETABLE_ENTRIES - 1) )
-            {
-                MEM_LOG("Unaligned superpage reference mfn %lx", mfn);
-                rc = -EINVAL;
-            }
-            else if ( !mfn_valid(mfn | (L1_PAGETABLE_ENTRIES - 1)) )
-                rc = -EINVAL;
-            else if ( op.cmd == MMUEXT_MARK_SUPER )
-                rc = mark_superpage(mfn_to_spage(mfn), d);
-            else
-                rc = unmark_superpage(mfn_to_spage(mfn));
-            break;
-        }
+            MEM_LOG("Superpages are deprecated.");
+            rc = -ENOSYS;
 
         default:
             MEM_LOG("Invalid extended pt command %#x", op.cmd);
diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index d97877d..eb08aa2 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -239,13 +239,8 @@ extern unsigned char boot_edid_info[128];
 #define XEN_VIRT_START          (HIRO_COMPAT_MPT_VIRT_END)
 #define XEN_VIRT_END            (XEN_VIRT_START + GB(1))
 
-/* Slot 261: superpage information array (64MB or 512MB). */
-#define SPAGETABLE_VIRT_END     FRAMETABLE_VIRT_START
-#define SPAGETABLE_NR           (((FRAMETABLE_NR - 1) >> (SUPERPAGE_SHIFT - \
-                                                          PAGE_SHIFT)) + 1)
-#define SPAGETABLE_SIZE         (SPAGETABLE_NR * sizeof(struct spage_info))
-#define SPAGETABLE_VIRT_START   ((SPAGETABLE_VIRT_END - SPAGETABLE_SIZE) & \
-                                 (_AC(-1,UL) << SUPERPAGE_SHIFT))
+/* Slot 261: superpage information array (64MB or 512MB).
+ * Now free. */
 
 #ifndef CONFIG_BIGMEM
 /* Slot 261: page-frame information array (128GB). */
diff --git a/xen/include/asm-x86/guest_pt.h b/xen/include/asm-x86/guest_pt.h
index 3447973..c163af6 100644
--- a/xen/include/asm-x86/guest_pt.h
+++ b/xen/include/asm-x86/guest_pt.h
@@ -186,9 +186,7 @@ guest_supports_superpages(struct vcpu *v)
     /* The _PAGE_PSE bit must be honoured in HVM guests, whenever
      * CR4.PSE is set or the guest is in PAE or long mode. 
      * It's also used in the dummy PT for vcpus with CR4.PG cleared. */
-    return (is_pv_vcpu(v)
-            ? opt_allow_superpage
-            : (GUEST_PAGING_LEVELS != 2 
+    return (is_pv_vcpu(v) ? 0 /* Deprecated. */ : (GUEST_PAGING_LEVELS != 2
                || !hvm_paging_enabled(v)
                || (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PSE)));
 }
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 7598414..7a0d258 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -233,21 +233,6 @@ struct page_info
 #define PGC_count_width   PG_shift(9)
 #define PGC_count_mask    ((1UL<<PGC_count_width)-1)
 
-struct spage_info
-{
-       unsigned long type_info;
-};
-
- /* The following page types are MUTUALLY EXCLUSIVE. */
-#define SGT_none          PG_mask(0, 2)  /* superpage not in use */
-#define SGT_mark          PG_mask(1, 2)  /* Marked as a superpage */
-#define SGT_dynamic       PG_mask(2, 2)  /* has been dynamically mapped as a superpage */
-#define SGT_type_mask     PG_mask(3, 2)  /* Bits 30-31 or 62-63. */
-
- /* Count of uses of this superpage as its current type. */
-#define SGT_count_width   PG_shift(3)
-#define SGT_count_mask    ((1UL<<SGT_count_width)-1)
-
 #define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
 #define is_xen_heap_mfn(mfn) \
     (__mfn_valid(mfn) && is_xen_heap_page(__mfn_to_page(mfn)))
@@ -281,7 +266,6 @@ extern void free_shared_domheap_page(struct page_info *page);
 
 #define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
 #define spage_table ((struct spage_info *)SPAGETABLE_VIRT_START)
-int get_superpage(unsigned long mfn, struct domain *d);
 extern unsigned long max_page;
 extern unsigned long total_pages;
 void init_frametable(void);
@@ -327,8 +311,6 @@ void zap_ro_mpt(unsigned long mfn);
 
 int is_iomem_page(unsigned long mfn);
 
-void clear_superpage_mark(struct page_info *page);
-
 const unsigned long *get_platform_badpages(unsigned int *array_size);
 /* Per page locks:
  * page_lock() is used for two purposes: pte serialization, and memory sharing.
@@ -402,7 +384,6 @@ static inline int get_page_and_type(struct page_info *page,
 
 int check_descriptor(const struct domain *, struct desc_struct *d);
 
-extern bool_t opt_allow_superpage;
 extern paddr_t mem_hotplug;
 
 /******************************************************************************
diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index 7b629b1..c3b290d 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -272,7 +272,8 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
  *  The one bits that does not fit with the default layout is the PAGE_PSE
  *  also called PAGE_PAT). The MMUEXT_[UN]MARK_SUPER arguments to the
  *  HYPERVISOR_mmuext_op serve as mechanism to set a pagetable to be 4MB
- *  (or 2MB) instead of using the PAGE_PSE bit.
+ *  (or 2MB) instead of using the PAGE_PSE bit. That functionality is now
+ *  deprecated and will return -ENOSYS.
  *
  *  The reason that the PAGE_PSE (bit 7) is not being utilized is due to Xen
  *  using it as the Page Attribute Table (PAT) bit - for details on it please
@@ -382,6 +383,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
  *
  * cmd: MMUEXT_[UN]MARK_SUPER
  * mfn: Machine frame number of head of superpage to be [un]marked.
+ * These sub-ops are deprecated and will return -ENOSYS.
  */
 /* ` enum mmuext_cmd { */
 #define MMUEXT_PIN_L1_TABLE      0
-- 
2.1.0

Re: [PATCH RFC] xen/libxl/libxl: RIP PV superpage.

[Jan Beulich]

>>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
> @@ -985,20 +968,7 @@ get_page_from_l2e(
>          return rc;
>      }
>  
> -    if ( !opt_allow_superpage )
> -    {
> -        MEM_LOG("Attempt to map superpage without allowsuperpage "
> -                "flag in hypervisor");
> -        return -EINVAL;
> -    }
> -
> -    if ( mfn & (L1_PAGETABLE_ENTRIES-1) )
> -    {
> -        MEM_LOG("Unaligned superpage map attempt mfn %lx", mfn);
> -        return -EINVAL;
> -    }
> -
> -    return get_superpage(mfn, d);
> +    return -EINVAL;
>  }

This return is now unreachable. You should instead remove the if()
around the code block right ahead of the code you delete here,
which is possible/correct due to _PAGE_PSE now always being in
L2_DISALLOW_MASK.

>  static void put_superpage(unsigned long mfn)
>  {
> -    struct spage_info *spage;
> -    unsigned long x, nx, y;
> -    unsigned long do_pages = 0;
> -
> -    if ( !opt_allow_superpage )
> -    {
> -        put_spage_pages(mfn_to_page(mfn));
> -        return;
> -    }
> -
> -    spage = mfn_to_spage(mfn);
> -    y = spage->type_info;
> -    do {
> -        x = y;
> -        nx = x - 1;
> -        if ((x & SGT_type_mask) == SGT_dynamic)
> -        {
> -            if ((nx & SGT_count_mask) == 0)
> -            {
> -                nx = (nx & ~SGT_type_mask) | SGT_none;
> -                do_pages = 1;
> -            }
> -        }
> -
> -    } while ((y = cmpxchg(&spage->type_info, x, nx)) != x);
> -
> -    if (do_pages)
> -        put_spage_pages(spage_to_page(spage));
> -
> -    return;
> +    ASSERT(1); /* This should really not be called. */
> +    put_spage_pages(mfn_to_page(mfn));
>  }

As follows from the reply to your intro mail, this ASSERT needs to
go away. But very likely it would be best to inline the body of
put_spage_pages() into its only caller, to not needlessly leave
traces of this super-page code.

> @@ -3437,29 +3231,8 @@ long do_mmuext_op(
>  
>          case MMUEXT_MARK_SUPER:
>          case MMUEXT_UNMARK_SUPER:
> -        {
> -            unsigned long mfn = op.arg1.mfn;
> -
> -            if ( !opt_allow_superpage )
> -            {
> -                MEM_LOG("Superpages disallowed");
> -                rc = -ENOSYS;
> -            }
> -            else if ( unlikely(d != pg_owner) )
> -                rc = -EPERM;
> -            else if ( mfn & (L1_PAGETABLE_ENTRIES - 1) )
> -            {
> -                MEM_LOG("Unaligned superpage reference mfn %lx", mfn);
> -                rc = -EINVAL;
> -            }
> -            else if ( !mfn_valid(mfn | (L1_PAGETABLE_ENTRIES - 1)) )
> -                rc = -EINVAL;
> -            else if ( op.cmd == MMUEXT_MARK_SUPER )
> -                rc = mark_superpage(mfn_to_spage(mfn), d);
> -            else
> -                rc = unmark_superpage(mfn_to_spage(mfn));
> -            break;
> -        }
> +            MEM_LOG("Superpages are deprecated.");
> +            rc = -ENOSYS;
>  
>          default:
>              MEM_LOG("Invalid extended pt command %#x", op.cmd);

I think having this handled by the default case would be good
enough. MEM_LOG() doesn't print anything in release builds
anyway, and for debug builds we don't need to do more than
the minimum here.

If you feel strongly about leaving the code in, you need to add
a break statement.

> --- a/xen/include/asm-x86/config.h
> +++ b/xen/include/asm-x86/config.h
> @@ -239,13 +239,8 @@ extern unsigned char boot_edid_info[128];
>  #define XEN_VIRT_START          (HIRO_COMPAT_MPT_VIRT_END)
>  #define XEN_VIRT_END            (XEN_VIRT_START + GB(1))
>  
> -/* Slot 261: superpage information array (64MB or 512MB). */
> -#define SPAGETABLE_VIRT_END     FRAMETABLE_VIRT_START
> -#define SPAGETABLE_NR           (((FRAMETABLE_NR - 1) >> (SUPERPAGE_SHIFT - \
> -                                                          PAGE_SHIFT)) + 1)
> -#define SPAGETABLE_SIZE         (SPAGETABLE_NR * sizeof(struct spage_info))
> -#define SPAGETABLE_VIRT_START   ((SPAGETABLE_VIRT_END - SPAGETABLE_SIZE) & \
> -                                 (_AC(-1,UL) << SUPERPAGE_SHIFT))
> +/* Slot 261: superpage information array (64MB or 512MB).
> + * Now free. */

No, this is too simple a change. You should update more places
and not leave this kind of a comment around.

> --- a/xen/include/asm-x86/guest_pt.h
> +++ b/xen/include/asm-x86/guest_pt.h
> @@ -186,9 +186,7 @@ guest_supports_superpages(struct vcpu *v)
>      /* The _PAGE_PSE bit must be honoured in HVM guests, whenever
>       * CR4.PSE is set or the guest is in PAE or long mode. 
>       * It's also used in the dummy PT for vcpus with CR4.PG cleared. */
> -    return (is_pv_vcpu(v)
> -            ? opt_allow_superpage
> -            : (GUEST_PAGING_LEVELS != 2 
> +    return (is_pv_vcpu(v) ? 0 /* Deprecated. */ : (GUEST_PAGING_LEVELS != 2
>                 || !hvm_paging_enabled(v)
>                 || (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PSE)));
>  }

No need for this "Deprecated" comment.

> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -272,7 +272,8 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
>   *  The one bits that does not fit with the default layout is the PAGE_PSE
>   *  also called PAGE_PAT). The MMUEXT_[UN]MARK_SUPER arguments to the
>   *  HYPERVISOR_mmuext_op serve as mechanism to set a pagetable to be 4MB
> - *  (or 2MB) instead of using the PAGE_PSE bit.
> + *  (or 2MB) instead of using the PAGE_PSE bit. That functionality is now
> + *  deprecated and will return -ENOSYS.
>   *
>   *  The reason that the PAGE_PSE (bit 7) is not being utilized is due to Xen
>   *  using it as the Page Attribute Table (PAT) bit - for details on it please
> @@ -382,6 +383,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
>   *
>   * cmd: MMUEXT_[UN]MARK_SUPER
>   * mfn: Machine frame number of head of superpage to be [un]marked.
> + * These sub-ops are deprecated and will return -ENOSYS.
>   */

"Deprecated" to means "do not use, but they still work".

Also you should be hiding their definitions inside an

#if __XEN_INTERFACE_VERSION__ < 0x00040700

Jan

Re: [PATCH RFC] xen/libxl/libxl: RIP PV superpage.

[Wei Liu]

You have two "libxl" in subject line.

On Fri, Jan 29, 2016 at 10:30:46AM -0500, Konrad Rzeszutek Wilk wrote:
> The last bastion of users is moving away from needing
> this.
> 
> Please note that there was an partial removal by
> c/s 9b3c6b13e0c085ceb53210f8e682a073096b94fa
> "libxc: remove superpages option for pv domains" so an user
> could not even run PV guests with superpage.
> 
> HVM guests are not affected - they have been able to use
> superpages (called hugepages) if the CPU supports 2MB or 1GB
> since Xen 3.3.
> 
> This is reported in the ring buffer:
> (XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB
> 
> AMD CPUs that support 2MB require NPT aka Rapid Virtualization
> Indexing. This was introduced in third generation Opteron -
> Barcelona.
> 
> Intel CPUs that support 2MB require EPT aka Extended Page Tables.
> This was introduced in Westmere microarchitecture.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  docs/misc/xen-command-line.markdown |   7 --
>  tools/libxc/include/xenguest.h      |   3 +-
>  tools/libxc/xc_nomigrate.c          |   2 +-
>  tools/libxc/xc_sr_restore.c         |   6 +-
>  tools/libxl/libxl_internal.h        |   2 +-
>  tools/libxl/libxl_save_callout.c    |   4 +-
>  tools/libxl/libxl_save_helper.c     |   3 +-
>  tools/libxl/libxl_stream_read.c     |   2 +-

Changes to toolstack code are done only to internal functions and only
delete the extra argument for superpage flag. They look sensible.

Wei.

Re: [PATCH RFC] Remove PV superpage support (v1).

[Jan Beulich]

>>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
> I am hoping the maintainers can guide me in how they would like:
>  - Deal with documentation? I removed the allowsuperpage from documentation
>    but perhaps it should just mention deprecated?

Since you delete the option, deleting it from doc seems fine to me.

>  - I left put_superpage as put_page_from_l2e calls it - but I can't see
>    how the _PAGE_PSE bit would be set as you won't be able to even
>    put that bit on (after my patch). Perhaps just make it an
>    ASSERT in put_page_from_l2e?

No, that can't be done. Did you check why it is the way it is
(having to do with the alternative initial P2M placement, which
does use superpages despite the guest itself not being able to
create any)?

Jan

Re: [PATCH RFC] Remove PV superpage support (v1).

[Konrad Rzeszutek Wilk]

On Fri, Jan 29, 2016 at 09:00:15AM -0700, Jan Beulich wrote:
> >>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
> > I am hoping the maintainers can guide me in how they would like:
> >  - Deal with documentation? I removed the allowsuperpage from documentation
> >    but perhaps it should just mention deprecated?
> 
> Since you delete the option, deleting it from doc seems fine to me.
> 
> >  - I left put_superpage as put_page_from_l2e calls it - but I can't see
> >    how the _PAGE_PSE bit would be set as you won't be able to even
> >    put that bit on (after my patch). Perhaps just make it an
> >    ASSERT in put_page_from_l2e?
> 
> No, that can't be done. Did you check why it is the way it is
> (having to do with the alternative initial P2M placement, which
> does use superpages despite the guest itself not being able to
> create any)?

If I recall - this was done for P2M array when put in a different virtual
address space? And this being only the initial domain - would this ..
Oh this can be done for normal guests as well I presume?

Time to dig in this a bit more.

> Jan
> 

Re: [PATCH RFC] Remove PV superpage support (v1).

[Jan Beulich]

>>> On 29.01.16 at 17:26, <konrad.wilk@oracle.com> wrote:
> On Fri, Jan 29, 2016 at 09:00:15AM -0700, Jan Beulich wrote:
>> >>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
>> > I am hoping the maintainers can guide me in how they would like:
>> >  - Deal with documentation? I removed the allowsuperpage from documentation
>> >    but perhaps it should just mention deprecated?
>> 
>> Since you delete the option, deleting it from doc seems fine to me.
>> 
>> >  - I left put_superpage as put_page_from_l2e calls it - but I can't see
>> >    how the _PAGE_PSE bit would be set as you won't be able to even
>> >    put that bit on (after my patch). Perhaps just make it an
>> >    ASSERT in put_page_from_l2e?
>> 
>> No, that can't be done. Did you check why it is the way it is
>> (having to do with the alternative initial P2M placement, which
>> does use superpages despite the guest itself not being able to
>> create any)?
> 
> If I recall - this was done for P2M array when put in a different virtual
> address space? And this being only the initial domain - would this ..
> Oh this can be done for normal guests as well I presume?

Iirc Jürgen enabled this for DomU too not so long ago.

Jan

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Re: [PATCH RFC] Remove PV superpage support (v1).

[Juergen Gross]

On 29/01/16 17:46, Jan Beulich wrote:
>>>> On 29.01.16 at 17:26, <konrad.wilk@oracle.com> wrote:
>> On Fri, Jan 29, 2016 at 09:00:15AM -0700, Jan Beulich wrote:
>>>>>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
>>>> I am hoping the maintainers can guide me in how they would like:
>>>>  - Deal with documentation? I removed the allowsuperpage from documentation
>>>>    but perhaps it should just mention deprecated?
>>>
>>> Since you delete the option, deleting it from doc seems fine to me.
>>>
>>>>  - I left put_superpage as put_page_from_l2e calls it - but I can't see
>>>>    how the _PAGE_PSE bit would be set as you won't be able to even
>>>>    put that bit on (after my patch). Perhaps just make it an
>>>>    ASSERT in put_page_from_l2e?
>>>
>>> No, that can't be done. Did you check why it is the way it is
>>> (having to do with the alternative initial P2M placement, which
>>> does use superpages despite the guest itself not being able to
>>> create any)?
>>
>> If I recall - this was done for P2M array when put in a different virtual
>> address space? And this being only the initial domain - would this ..
>> Oh this can be done for normal guests as well I presume?
> 
> Iirc Jürgen enabled this for DomU too not so long ago.

I did. The Xen tools won't use superpages for the p2m array, however.


Juergen

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Re: [PATCH RFC] Remove PV superpage support (v1).

[Jan Beulich]

>>> On 01.02.16 at 05:54, <JGross@suse.com> wrote:
> On 29/01/16 17:46, Jan Beulich wrote:
>>>>> On 29.01.16 at 17:26, <konrad.wilk@oracle.com> wrote:
>>> On Fri, Jan 29, 2016 at 09:00:15AM -0700, Jan Beulich wrote:
>>>>>>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
>>>>> I am hoping the maintainers can guide me in how they would like:
>>>>>  - Deal with documentation? I removed the allowsuperpage from documentation
>>>>>    but perhaps it should just mention deprecated?
>>>>
>>>> Since you delete the option, deleting it from doc seems fine to me.
>>>>
>>>>>  - I left put_superpage as put_page_from_l2e calls it - but I can't see
>>>>>    how the _PAGE_PSE bit would be set as you won't be able to even
>>>>>    put that bit on (after my patch). Perhaps just make it an
>>>>>    ASSERT in put_page_from_l2e?
>>>>
>>>> No, that can't be done. Did you check why it is the way it is
>>>> (having to do with the alternative initial P2M placement, which
>>>> does use superpages despite the guest itself not being able to
>>>> create any)?
>>>
>>> If I recall - this was done for P2M array when put in a different virtual
>>> address space? And this being only the initial domain - would this ..
>>> Oh this can be done for normal guests as well I presume?
>> 
>> Iirc Jürgen enabled this for DomU too not so long ago.
> 
> I did. The Xen tools won't use superpages for the p2m array, however.

That's unfortunate. Is there a reason for this?

Jan

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Re: [PATCH RFC] Remove PV superpage support (v1).

[Juergen Gross]

On 01/02/16 08:53, Jan Beulich wrote:
>>>> On 01.02.16 at 05:54, <JGross@suse.com> wrote:
>> On 29/01/16 17:46, Jan Beulich wrote:
>>>>>> On 29.01.16 at 17:26, <konrad.wilk@oracle.com> wrote:
>>>> On Fri, Jan 29, 2016 at 09:00:15AM -0700, Jan Beulich wrote:
>>>>>>>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
>>>>>> I am hoping the maintainers can guide me in how they would like:
>>>>>>  - Deal with documentation? I removed the allowsuperpage from documentation
>>>>>>    but perhaps it should just mention deprecated?
>>>>>
>>>>> Since you delete the option, deleting it from doc seems fine to me.
>>>>>
>>>>>>  - I left put_superpage as put_page_from_l2e calls it - but I can't see
>>>>>>    how the _PAGE_PSE bit would be set as you won't be able to even
>>>>>>    put that bit on (after my patch). Perhaps just make it an
>>>>>>    ASSERT in put_page_from_l2e?
>>>>>
>>>>> No, that can't be done. Did you check why it is the way it is
>>>>> (having to do with the alternative initial P2M placement, which
>>>>> does use superpages despite the guest itself not being able to
>>>>> create any)?
>>>>
>>>> If I recall - this was done for P2M array when put in a different virtual
>>>> address space? And this being only the initial domain - would this ..
>>>> Oh this can be done for normal guests as well I presume?
>>>
>>> Iirc Jürgen enabled this for DomU too not so long ago.
>>
>> I did. The Xen tools won't use superpages for the p2m array, however.
> 
> That's unfortunate. Is there a reason for this?

It's a matter of complexity. Adding superpage usage for the p2m array
would add quite some code to the tools without a real gain, as the domU
will have to split the superpage in any case in order to be able to
support migration of the domain. So the only gain would be to save
about 0.2% of memory footprint while booting the kernel (when the kernel
is up the difference would be zero).

Juergen

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Re: [PATCH RFC] Remove PV superpage support (v1).

[Jan Beulich]

>>> On 01.02.16 at 09:03, <JGross@suse.com> wrote:
> On 01/02/16 08:53, Jan Beulich wrote:
>>>>> On 01.02.16 at 05:54, <JGross@suse.com> wrote:
>>> On 29/01/16 17:46, Jan Beulich wrote:
>>>>>>> On 29.01.16 at 17:26, <konrad.wilk@oracle.com> wrote:
>>>>> On Fri, Jan 29, 2016 at 09:00:15AM -0700, Jan Beulich wrote:
>>>>>>>>> On 29.01.16 at 16:30, <konrad.wilk@oracle.com> wrote:
>>>>>>> I am hoping the maintainers can guide me in how they would like:
>>>>>>>  - Deal with documentation? I removed the allowsuperpage from documentation
>>>>>>>    but perhaps it should just mention deprecated?
>>>>>>
>>>>>> Since you delete the option, deleting it from doc seems fine to me.
>>>>>>
>>>>>>>  - I left put_superpage as put_page_from_l2e calls it - but I can't see
>>>>>>>    how the _PAGE_PSE bit would be set as you won't be able to even
>>>>>>>    put that bit on (after my patch). Perhaps just make it an
>>>>>>>    ASSERT in put_page_from_l2e?
>>>>>>
>>>>>> No, that can't be done. Did you check why it is the way it is
>>>>>> (having to do with the alternative initial P2M placement, which
>>>>>> does use superpages despite the guest itself not being able to
>>>>>> create any)?
>>>>>
>>>>> If I recall - this was done for P2M array when put in a different virtual
>>>>> address space? And this being only the initial domain - would this ..
>>>>> Oh this can be done for normal guests as well I presume?
>>>>
>>>> Iirc Jürgen enabled this for DomU too not so long ago.
>>>
>>> I did. The Xen tools won't use superpages for the p2m array, however.
>> 
>> That's unfortunate. Is there a reason for this?
> 
> It's a matter of complexity. Adding superpage usage for the p2m array
> would add quite some code to the tools without a real gain, as the domU
> will have to split the superpage in any case in order to be able to
> support migration of the domain. So the only gain would be to save
> about 0.2% of memory footprint while booting the kernel (when the kernel
> is up the difference would be zero).

Okay, makes sense. I just assumed that like in the Dom0 case
the code to set up the table would have been new anyway (due
to which in the Dom0 case it was actually natural to use large
pages where possible).

Jan

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Re: [PATCH RFC] Remove PV superpage support (v1).

[Ian Campbell]

On Fri, 2016-01-29 at 10:30 -0500, Konrad Rzeszutek Wilk wrote:
>  - Deal with documentation? I removed the allowsuperpage from
> documentation
>    but perhaps it should just mention deprecated?

"deprecated" means "still available but use is discouraged". Since AIUI you
really are removing PV superpages here calling it deprecated would be
wrong. I think you should just remove all mentions of it from the
documentation.

Ian.

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