diff mbox series

[v2,02/34] s390: Use _pt_s390_gaddr for gmap address tracking

Message ID 20230501192829.17086-3-vishal.moola@gmail.com (mailing list archive)
State New
Headers show
Series Split ptdesc from struct page | expand

Commit Message

Vishal Moola May 1, 2023, 7:27 p.m. UTC 
s390 uses page->index to keep track of page tables for the guest address
space. In an attempt to consolidate the usage of page fields in s390,
replace _pt_pad_2 with _pt_s390_gaddr to replace page->index in gmap.

This will help with the splitting of struct ptdesc from struct page, as
well as allow s390 to use _pt_frag_refcount for fragmented page table
tracking.

Since page->_pt_s390_gaddr aliases with mapping, ensure its set to NULL
before freeing the pages as well.

This also reverts commit 7e25de77bc5ea ("s390/mm: use pmd_pgtable_page()
helper in __gmap_segment_gaddr()") which had s390 use
pmd_pgtable_page() to get a gmap page table, as pmd_pgtable_page()
should be used for more generic process page tables.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
---
 arch/s390/mm/gmap.c      | 56 +++++++++++++++++++++++++++-------------
 include/linux/mm_types.h |  2 +-
 2 files changed, 39 insertions(+), 19 deletions(-)

Comments

Mike Rapoport May 25, 2023, 8:58 a.m. UTC | #1 
On Mon, May 01, 2023 at 12:27:57PM -0700, Vishal Moola (Oracle) wrote:
> s390 uses page->index to keep track of page tables for the guest address
> space. In an attempt to consolidate the usage of page fields in s390,
> replace _pt_pad_2 with _pt_s390_gaddr to replace page->index in gmap.
> 
> This will help with the splitting of struct ptdesc from struct page, as
> well as allow s390 to use _pt_frag_refcount for fragmented page table
> tracking.
> 
> Since page->_pt_s390_gaddr aliases with mapping, ensure its set to NULL
> before freeing the pages as well.

Wouldn't it be easier to use _pt_pad_1 which is aliased with lru and that
does not seem to be used by page tables at all?
 
> This also reverts commit 7e25de77bc5ea ("s390/mm: use pmd_pgtable_page()
> helper in __gmap_segment_gaddr()") which had s390 use
> pmd_pgtable_page() to get a gmap page table, as pmd_pgtable_page()
> should be used for more generic process page tables.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
> ---
>  arch/s390/mm/gmap.c      | 56 +++++++++++++++++++++++++++-------------
>  include/linux/mm_types.h |  2 +-
>  2 files changed, 39 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index dfe905c7bd8e..a9e8b1805894 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -70,7 +70,7 @@ static struct gmap *gmap_alloc(unsigned long limit)
>  	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
>  	if (!page)
>  		goto out_free;
> -	page->index = 0;
> +	page->_pt_s390_gaddr = 0;
>  	list_add(&page->lru, &gmap->crst_list);
>  	table = page_to_virt(page);
>  	crst_table_init(table, etype);
> @@ -187,16 +187,20 @@ static void gmap_free(struct gmap *gmap)
>  	if (!(gmap_is_shadow(gmap) && gmap->removed))
>  		gmap_flush_tlb(gmap);
>  	/* Free all segment & region tables. */
> -	list_for_each_entry_safe(page, next, &gmap->crst_list, lru)
> +	list_for_each_entry_safe(page, next, &gmap->crst_list, lru) {
> +		page->_pt_s390_gaddr = 0;
>  		__free_pages(page, CRST_ALLOC_ORDER);
> +	}
>  	gmap_radix_tree_free(&gmap->guest_to_host);
>  	gmap_radix_tree_free(&gmap->host_to_guest);
>  
>  	/* Free additional data for a shadow gmap */
>  	if (gmap_is_shadow(gmap)) {
>  		/* Free all page tables. */
> -		list_for_each_entry_safe(page, next, &gmap->pt_list, lru)
> +		list_for_each_entry_safe(page, next, &gmap->pt_list, lru) {
> +			page->_pt_s390_gaddr = 0;
>  			page_table_free_pgste(page);
> +		}
>  		gmap_rmap_radix_tree_free(&gmap->host_to_rmap);
>  		/* Release reference to the parent */
>  		gmap_put(gmap->parent);
> @@ -318,12 +322,14 @@ static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
>  		list_add(&page->lru, &gmap->crst_list);
>  		*table = __pa(new) | _REGION_ENTRY_LENGTH |
>  			(*table & _REGION_ENTRY_TYPE_MASK);
> -		page->index = gaddr;
> +		page->_pt_s390_gaddr = gaddr;
>  		page = NULL;
>  	}
>  	spin_unlock(&gmap->guest_table_lock);
> -	if (page)
> +	if (page) {
> +		page->_pt_s390_gaddr = 0;
>  		__free_pages(page, CRST_ALLOC_ORDER);
> +	}
>  	return 0;
>  }
>  
> @@ -336,12 +342,14 @@ static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
>  static unsigned long __gmap_segment_gaddr(unsigned long *entry)
>  {
>  	struct page *page;
> -	unsigned long offset;
> +	unsigned long offset, mask;
>  
>  	offset = (unsigned long) entry / sizeof(unsigned long);
>  	offset = (offset & (PTRS_PER_PMD - 1)) * PMD_SIZE;
> -	page = pmd_pgtable_page((pmd_t *) entry);
> -	return page->index + offset;
> +	mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
> +	page = virt_to_page((void *)((unsigned long) entry & mask));
> +
> +	return page->_pt_s390_gaddr + offset;
>  }
>  
>  /**
> @@ -1351,6 +1359,7 @@ static void gmap_unshadow_pgt(struct gmap *sg, unsigned long raddr)
>  	/* Free page table */
>  	page = phys_to_page(pgt);
>  	list_del(&page->lru);
> +	page->_pt_s390_gaddr = 0;
>  	page_table_free_pgste(page);
>  }
>  
> @@ -1379,6 +1388,7 @@ static void __gmap_unshadow_sgt(struct gmap *sg, unsigned long raddr,
>  		/* Free page table */
>  		page = phys_to_page(pgt);
>  		list_del(&page->lru);
> +		page->_pt_s390_gaddr = 0;
>  		page_table_free_pgste(page);
>  	}
>  }
> @@ -1409,6 +1419,7 @@ static void gmap_unshadow_sgt(struct gmap *sg, unsigned long raddr)
>  	/* Free segment table */
>  	page = phys_to_page(sgt);
>  	list_del(&page->lru);
> +	page->_pt_s390_gaddr = 0;
>  	__free_pages(page, CRST_ALLOC_ORDER);
>  }
>  
> @@ -1437,6 +1448,7 @@ static void __gmap_unshadow_r3t(struct gmap *sg, unsigned long raddr,
>  		/* Free segment table */
>  		page = phys_to_page(sgt);
>  		list_del(&page->lru);
> +		page->_pt_s390_gaddr = 0;
>  		__free_pages(page, CRST_ALLOC_ORDER);
>  	}
>  }
> @@ -1467,6 +1479,7 @@ static void gmap_unshadow_r3t(struct gmap *sg, unsigned long raddr)
>  	/* Free region 3 table */
>  	page = phys_to_page(r3t);
>  	list_del(&page->lru);
> +	page->_pt_s390_gaddr = 0;
>  	__free_pages(page, CRST_ALLOC_ORDER);
>  }
>  
> @@ -1495,6 +1508,7 @@ static void __gmap_unshadow_r2t(struct gmap *sg, unsigned long raddr,
>  		/* Free region 3 table */
>  		page = phys_to_page(r3t);
>  		list_del(&page->lru);
> +		page->_pt_s390_gaddr = 0;
>  		__free_pages(page, CRST_ALLOC_ORDER);
>  	}
>  }
> @@ -1525,6 +1539,7 @@ static void gmap_unshadow_r2t(struct gmap *sg, unsigned long raddr)
>  	/* Free region 2 table */
>  	page = phys_to_page(r2t);
>  	list_del(&page->lru);
> +	page->_pt_s390_gaddr = 0;
>  	__free_pages(page, CRST_ALLOC_ORDER);
>  }
>  
> @@ -1557,6 +1572,7 @@ static void __gmap_unshadow_r1t(struct gmap *sg, unsigned long raddr,
>  		/* Free region 2 table */
>  		page = phys_to_page(r2t);
>  		list_del(&page->lru);
> +		page->_pt_s390_gaddr = 0;
>  		__free_pages(page, CRST_ALLOC_ORDER);
>  	}
>  }
> @@ -1762,9 +1778,9 @@ int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
>  	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
>  	if (!page)
>  		return -ENOMEM;
> -	page->index = r2t & _REGION_ENTRY_ORIGIN;
> +	page->_pt_s390_gaddr = r2t & _REGION_ENTRY_ORIGIN;
>  	if (fake)
> -		page->index |= GMAP_SHADOW_FAKE_TABLE;
> +		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
>  	s_r2t = page_to_phys(page);
>  	/* Install shadow region second table */
>  	spin_lock(&sg->guest_table_lock);
> @@ -1814,6 +1830,7 @@ int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
>  	return rc;
>  out_free:
>  	spin_unlock(&sg->guest_table_lock);
> +	page->_pt_s390_gaddr = 0;
>  	__free_pages(page, CRST_ALLOC_ORDER);
>  	return rc;
>  }
> @@ -1846,9 +1863,9 @@ int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
>  	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
>  	if (!page)
>  		return -ENOMEM;
> -	page->index = r3t & _REGION_ENTRY_ORIGIN;
> +	page->_pt_s390_gaddr = r3t & _REGION_ENTRY_ORIGIN;
>  	if (fake)
> -		page->index |= GMAP_SHADOW_FAKE_TABLE;
> +		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
>  	s_r3t = page_to_phys(page);
>  	/* Install shadow region second table */
>  	spin_lock(&sg->guest_table_lock);
> @@ -1898,6 +1915,7 @@ int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
>  	return rc;
>  out_free:
>  	spin_unlock(&sg->guest_table_lock);
> +	page->_pt_s390_gaddr = 0;
>  	__free_pages(page, CRST_ALLOC_ORDER);
>  	return rc;
>  }
> @@ -1930,9 +1948,9 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
>  	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
>  	if (!page)
>  		return -ENOMEM;
> -	page->index = sgt & _REGION_ENTRY_ORIGIN;
> +	page->_pt_s390_gaddr = sgt & _REGION_ENTRY_ORIGIN;
>  	if (fake)
> -		page->index |= GMAP_SHADOW_FAKE_TABLE;
> +		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
>  	s_sgt = page_to_phys(page);
>  	/* Install shadow region second table */
>  	spin_lock(&sg->guest_table_lock);
> @@ -1982,6 +2000,7 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
>  	return rc;
>  out_free:
>  	spin_unlock(&sg->guest_table_lock);
> +	page->_pt_s390_gaddr = 0;
>  	__free_pages(page, CRST_ALLOC_ORDER);
>  	return rc;
>  }
> @@ -2014,9 +2033,9 @@ int gmap_shadow_pgt_lookup(struct gmap *sg, unsigned long saddr,
>  	if (table && !(*table & _SEGMENT_ENTRY_INVALID)) {
>  		/* Shadow page tables are full pages (pte+pgste) */
>  		page = pfn_to_page(*table >> PAGE_SHIFT);
> -		*pgt = page->index & ~GMAP_SHADOW_FAKE_TABLE;
> +		*pgt = page->_pt_s390_gaddr & ~GMAP_SHADOW_FAKE_TABLE;
>  		*dat_protection = !!(*table & _SEGMENT_ENTRY_PROTECT);
> -		*fake = !!(page->index & GMAP_SHADOW_FAKE_TABLE);
> +		*fake = !!(page->_pt_s390_gaddr & GMAP_SHADOW_FAKE_TABLE);
>  		rc = 0;
>  	} else  {
>  		rc = -EAGAIN;
> @@ -2054,9 +2073,9 @@ int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
>  	page = page_table_alloc_pgste(sg->mm);
>  	if (!page)
>  		return -ENOMEM;
> -	page->index = pgt & _SEGMENT_ENTRY_ORIGIN;
> +	page->_pt_s390_gaddr = pgt & _SEGMENT_ENTRY_ORIGIN;
>  	if (fake)
> -		page->index |= GMAP_SHADOW_FAKE_TABLE;
> +		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
>  	s_pgt = page_to_phys(page);
>  	/* Install shadow page table */
>  	spin_lock(&sg->guest_table_lock);
> @@ -2101,6 +2120,7 @@ int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
>  	return rc;
>  out_free:
>  	spin_unlock(&sg->guest_table_lock);
> +	page->_pt_s390_gaddr = 0;
>  	page_table_free_pgste(page);
>  	return rc;
>  
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 306a3d1a0fa6..6161fe1ae5b8 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -144,7 +144,7 @@ struct page {
>  		struct {	/* Page table pages */
>  			unsigned long _pt_pad_1;	/* compound_head */
>  			pgtable_t pmd_huge_pte; /* protected by page->ptl */
> -			unsigned long _pt_pad_2;	/* mapping */
> +			unsigned long _pt_s390_gaddr;	/* mapping */
>  			union {
>  				struct mm_struct *pt_mm; /* x86 pgds only */
>  				atomic_t pt_frag_refcount; /* powerpc */
> -- 
> 2.39.2
> 
>
Vishal Moola May 25, 2023, 5:12 p.m. UTC | #2 
On Thu, May 25, 2023 at 1:58 AM Mike Rapoport <rppt@kernel.org> wrote:
>
> On Mon, May 01, 2023 at 12:27:57PM -0700, Vishal Moola (Oracle) wrote:
> > s390 uses page->index to keep track of page tables for the guest address
> > space. In an attempt to consolidate the usage of page fields in s390,
> > replace _pt_pad_2 with _pt_s390_gaddr to replace page->index in gmap.
> >
> > This will help with the splitting of struct ptdesc from struct page, as
> > well as allow s390 to use _pt_frag_refcount for fragmented page table
> > tracking.
> >
> > Since page->_pt_s390_gaddr aliases with mapping, ensure its set to NULL
> > before freeing the pages as well.
>
> Wouldn't it be easier to use _pt_pad_1 which is aliased with lru and that
> does not seem to be used by page tables at all?

I initially thought the same, but s390 page tables use lru.
diff mbox series

Patch

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index dfe905c7bd8e..a9e8b1805894 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -70,7 +70,7 @@  static struct gmap *gmap_alloc(unsigned long limit)
 	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
 	if (!page)
 		goto out_free;
-	page->index = 0;
+	page->_pt_s390_gaddr = 0;
 	list_add(&page->lru, &gmap->crst_list);
 	table = page_to_virt(page);
 	crst_table_init(table, etype);
@@ -187,16 +187,20 @@  static void gmap_free(struct gmap *gmap)
 	if (!(gmap_is_shadow(gmap) && gmap->removed))
 		gmap_flush_tlb(gmap);
 	/* Free all segment & region tables. */
-	list_for_each_entry_safe(page, next, &gmap->crst_list, lru)
+	list_for_each_entry_safe(page, next, &gmap->crst_list, lru) {
+		page->_pt_s390_gaddr = 0;
 		__free_pages(page, CRST_ALLOC_ORDER);
+	}
 	gmap_radix_tree_free(&gmap->guest_to_host);
 	gmap_radix_tree_free(&gmap->host_to_guest);
 
 	/* Free additional data for a shadow gmap */
 	if (gmap_is_shadow(gmap)) {
 		/* Free all page tables. */
-		list_for_each_entry_safe(page, next, &gmap->pt_list, lru)
+		list_for_each_entry_safe(page, next, &gmap->pt_list, lru) {
+			page->_pt_s390_gaddr = 0;
 			page_table_free_pgste(page);
+		}
 		gmap_rmap_radix_tree_free(&gmap->host_to_rmap);
 		/* Release reference to the parent */
 		gmap_put(gmap->parent);
@@ -318,12 +322,14 @@  static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
 		list_add(&page->lru, &gmap->crst_list);
 		*table = __pa(new) | _REGION_ENTRY_LENGTH |
 			(*table & _REGION_ENTRY_TYPE_MASK);
-		page->index = gaddr;
+		page->_pt_s390_gaddr = gaddr;
 		page = NULL;
 	}
 	spin_unlock(&gmap->guest_table_lock);
-	if (page)
+	if (page) {
+		page->_pt_s390_gaddr = 0;
 		__free_pages(page, CRST_ALLOC_ORDER);
+	}
 	return 0;
 }
 
@@ -336,12 +342,14 @@  static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
 static unsigned long __gmap_segment_gaddr(unsigned long *entry)
 {
 	struct page *page;
-	unsigned long offset;
+	unsigned long offset, mask;
 
 	offset = (unsigned long) entry / sizeof(unsigned long);
 	offset = (offset & (PTRS_PER_PMD - 1)) * PMD_SIZE;
-	page = pmd_pgtable_page((pmd_t *) entry);
-	return page->index + offset;
+	mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
+	page = virt_to_page((void *)((unsigned long) entry & mask));
+
+	return page->_pt_s390_gaddr + offset;
 }
 
 /**
@@ -1351,6 +1359,7 @@  static void gmap_unshadow_pgt(struct gmap *sg, unsigned long raddr)
 	/* Free page table */
 	page = phys_to_page(pgt);
 	list_del(&page->lru);
+	page->_pt_s390_gaddr = 0;
 	page_table_free_pgste(page);
 }
 
@@ -1379,6 +1388,7 @@  static void __gmap_unshadow_sgt(struct gmap *sg, unsigned long raddr,
 		/* Free page table */
 		page = phys_to_page(pgt);
 		list_del(&page->lru);
+		page->_pt_s390_gaddr = 0;
 		page_table_free_pgste(page);
 	}
 }
@@ -1409,6 +1419,7 @@  static void gmap_unshadow_sgt(struct gmap *sg, unsigned long raddr)
 	/* Free segment table */
 	page = phys_to_page(sgt);
 	list_del(&page->lru);
+	page->_pt_s390_gaddr = 0;
 	__free_pages(page, CRST_ALLOC_ORDER);
 }
 
@@ -1437,6 +1448,7 @@  static void __gmap_unshadow_r3t(struct gmap *sg, unsigned long raddr,
 		/* Free segment table */
 		page = phys_to_page(sgt);
 		list_del(&page->lru);
+		page->_pt_s390_gaddr = 0;
 		__free_pages(page, CRST_ALLOC_ORDER);
 	}
 }
@@ -1467,6 +1479,7 @@  static void gmap_unshadow_r3t(struct gmap *sg, unsigned long raddr)
 	/* Free region 3 table */
 	page = phys_to_page(r3t);
 	list_del(&page->lru);
+	page->_pt_s390_gaddr = 0;
 	__free_pages(page, CRST_ALLOC_ORDER);
 }
 
@@ -1495,6 +1508,7 @@  static void __gmap_unshadow_r2t(struct gmap *sg, unsigned long raddr,
 		/* Free region 3 table */
 		page = phys_to_page(r3t);
 		list_del(&page->lru);
+		page->_pt_s390_gaddr = 0;
 		__free_pages(page, CRST_ALLOC_ORDER);
 	}
 }
@@ -1525,6 +1539,7 @@  static void gmap_unshadow_r2t(struct gmap *sg, unsigned long raddr)
 	/* Free region 2 table */
 	page = phys_to_page(r2t);
 	list_del(&page->lru);
+	page->_pt_s390_gaddr = 0;
 	__free_pages(page, CRST_ALLOC_ORDER);
 }
 
@@ -1557,6 +1572,7 @@  static void __gmap_unshadow_r1t(struct gmap *sg, unsigned long raddr,
 		/* Free region 2 table */
 		page = phys_to_page(r2t);
 		list_del(&page->lru);
+		page->_pt_s390_gaddr = 0;
 		__free_pages(page, CRST_ALLOC_ORDER);
 	}
 }
@@ -1762,9 +1778,9 @@  int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
 	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
 	if (!page)
 		return -ENOMEM;
-	page->index = r2t & _REGION_ENTRY_ORIGIN;
+	page->_pt_s390_gaddr = r2t & _REGION_ENTRY_ORIGIN;
 	if (fake)
-		page->index |= GMAP_SHADOW_FAKE_TABLE;
+		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
 	s_r2t = page_to_phys(page);
 	/* Install shadow region second table */
 	spin_lock(&sg->guest_table_lock);
@@ -1814,6 +1830,7 @@  int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
 	return rc;
 out_free:
 	spin_unlock(&sg->guest_table_lock);
+	page->_pt_s390_gaddr = 0;
 	__free_pages(page, CRST_ALLOC_ORDER);
 	return rc;
 }
@@ -1846,9 +1863,9 @@  int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
 	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
 	if (!page)
 		return -ENOMEM;
-	page->index = r3t & _REGION_ENTRY_ORIGIN;
+	page->_pt_s390_gaddr = r3t & _REGION_ENTRY_ORIGIN;
 	if (fake)
-		page->index |= GMAP_SHADOW_FAKE_TABLE;
+		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
 	s_r3t = page_to_phys(page);
 	/* Install shadow region second table */
 	spin_lock(&sg->guest_table_lock);
@@ -1898,6 +1915,7 @@  int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
 	return rc;
 out_free:
 	spin_unlock(&sg->guest_table_lock);
+	page->_pt_s390_gaddr = 0;
 	__free_pages(page, CRST_ALLOC_ORDER);
 	return rc;
 }
@@ -1930,9 +1948,9 @@  int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
 	page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
 	if (!page)
 		return -ENOMEM;
-	page->index = sgt & _REGION_ENTRY_ORIGIN;
+	page->_pt_s390_gaddr = sgt & _REGION_ENTRY_ORIGIN;
 	if (fake)
-		page->index |= GMAP_SHADOW_FAKE_TABLE;
+		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
 	s_sgt = page_to_phys(page);
 	/* Install shadow region second table */
 	spin_lock(&sg->guest_table_lock);
@@ -1982,6 +2000,7 @@  int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
 	return rc;
 out_free:
 	spin_unlock(&sg->guest_table_lock);
+	page->_pt_s390_gaddr = 0;
 	__free_pages(page, CRST_ALLOC_ORDER);
 	return rc;
 }
@@ -2014,9 +2033,9 @@  int gmap_shadow_pgt_lookup(struct gmap *sg, unsigned long saddr,
 	if (table && !(*table & _SEGMENT_ENTRY_INVALID)) {
 		/* Shadow page tables are full pages (pte+pgste) */
 		page = pfn_to_page(*table >> PAGE_SHIFT);
-		*pgt = page->index & ~GMAP_SHADOW_FAKE_TABLE;
+		*pgt = page->_pt_s390_gaddr & ~GMAP_SHADOW_FAKE_TABLE;
 		*dat_protection = !!(*table & _SEGMENT_ENTRY_PROTECT);
-		*fake = !!(page->index & GMAP_SHADOW_FAKE_TABLE);
+		*fake = !!(page->_pt_s390_gaddr & GMAP_SHADOW_FAKE_TABLE);
 		rc = 0;
 	} else  {
 		rc = -EAGAIN;
@@ -2054,9 +2073,9 @@  int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
 	page = page_table_alloc_pgste(sg->mm);
 	if (!page)
 		return -ENOMEM;
-	page->index = pgt & _SEGMENT_ENTRY_ORIGIN;
+	page->_pt_s390_gaddr = pgt & _SEGMENT_ENTRY_ORIGIN;
 	if (fake)
-		page->index |= GMAP_SHADOW_FAKE_TABLE;
+		page->_pt_s390_gaddr |= GMAP_SHADOW_FAKE_TABLE;
 	s_pgt = page_to_phys(page);
 	/* Install shadow page table */
 	spin_lock(&sg->guest_table_lock);
@@ -2101,6 +2120,7 @@  int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
 	return rc;
 out_free:
 	spin_unlock(&sg->guest_table_lock);
+	page->_pt_s390_gaddr = 0;
 	page_table_free_pgste(page);
 	return rc;
 
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 306a3d1a0fa6..6161fe1ae5b8 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -144,7 +144,7 @@  struct page {
 		struct {	/* Page table pages */
 			unsigned long _pt_pad_1;	/* compound_head */
 			pgtable_t pmd_huge_pte; /* protected by page->ptl */
-			unsigned long _pt_pad_2;	/* mapping */
+			unsigned long _pt_s390_gaddr;	/* mapping */
 			union {
 				struct mm_struct *pt_mm; /* x86 pgds only */
 				atomic_t pt_frag_refcount; /* powerpc */