KVM: s390: remove the last user of page->index

Shadow page tables use page->index to keep the g2 address of the guest
page table being shadowed.

Instead of keeping the information in page->index, split the address
and smear it over the 16-bit softbits areas of 4 PGSTEs.

This removes the last s390 user of page->index.

Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Link: https://lore.kernel.org/r/20250123144627.312456-16-imbrenda@linux.ibm.com
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250123144627.312456-16-imbrenda@linux.ibm.com>

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index a96bde2e5f18de42f271601661523f983183c4e8..3ca5af4cfe432e24d2484f7cb48b0393697a84bb 100644 (file)
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -420,6 +420,7 @@ void setup_protection_map(void);
 #define PGSTE_HC_BIT   0x0020000000000000UL
 #define PGSTE_GR_BIT   0x0004000000000000UL
 #define PGSTE_GC_BIT   0x0002000000000000UL
+#define PGSTE_ST2_MASK 0x0000ffff00000000UL
 #define PGSTE_UC_BIT   0x0000000000008000UL    /* user dirty (migration) */
 #define PGSTE_IN_BIT   0x0000000000004000UL    /* IPTE notify bit */
 #define PGSTE_VSIE_BIT 0x0000000000002000UL    /* ref'd in a shadow table */
@@ -2007,4 +2008,18 @@ extern void s390_reset_cmma(struct mm_struct *mm);
 #define pmd_pgtable(pmd) \
        ((pgtable_t)__va(pmd_val(pmd) & -sizeof(pte_t)*PTRS_PER_PTE))
 
+static inline unsigned long gmap_pgste_get_pgt_addr(unsigned long *pgt)
+{
+       unsigned long *pgstes, res;
+
+       pgstes = pgt + _PAGE_ENTRIES;
+
+       res = (pgstes[0] & PGSTE_ST2_MASK) << 16;
+       res |= pgstes[1] & PGSTE_ST2_MASK;
+       res |= (pgstes[2] & PGSTE_ST2_MASK) >> 16;
+       res |= (pgstes[3] & PGSTE_ST2_MASK) >> 32;
+
+       return res;
+}
+
 #endif /* _S390_PAGE_H */

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index bb1340389369cbc8877a3af3933349f775699f07..f6fded15633ad87f6b02c2c42aea35a3c9164253 100644 (file)
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1409,6 +1409,7 @@ shadow_pgt:
 static int shadow_pgt_lookup(struct gmap *sg, unsigned long saddr, unsigned long *pgt,
                             int *dat_protection, int *fake)
 {
+       unsigned long pt_index;
        unsigned long *table;
        struct page *page;
        int rc;
@@ -1418,9 +1419,10 @@ static int shadow_pgt_lookup(struct gmap *sg, unsigned long saddr, unsigned long
        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;
+               pt_index = gmap_pgste_get_pgt_addr(page_to_virt(page));
+               *pgt = pt_index & ~GMAP_SHADOW_FAKE_TABLE;
                *dat_protection = !!(*table & _SEGMENT_ENTRY_PROTECT);
-               *fake = !!(page->index & GMAP_SHADOW_FAKE_TABLE);
+               *fake = !!(pt_index & GMAP_SHADOW_FAKE_TABLE);
                rc = 0;
        } else  {
                rc = -EAGAIN;

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 38f04432170408f1de3542d6299c20b8623c1e11..94d9277858009d7b96be717786485b1694c18534 100644 (file)
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -1733,6 +1733,23 @@ out_free:
 }
 EXPORT_SYMBOL_GPL(gmap_shadow_sgt);
 
+static void gmap_pgste_set_pgt_addr(struct ptdesc *ptdesc, unsigned long pgt_addr)
+{
+       unsigned long *pgstes = page_to_virt(ptdesc_page(ptdesc));
+
+       pgstes += _PAGE_ENTRIES;
+
+       pgstes[0] &= ~PGSTE_ST2_MASK;
+       pgstes[1] &= ~PGSTE_ST2_MASK;
+       pgstes[2] &= ~PGSTE_ST2_MASK;
+       pgstes[3] &= ~PGSTE_ST2_MASK;
+
+       pgstes[0] |= (pgt_addr >> 16) & PGSTE_ST2_MASK;
+       pgstes[1] |= pgt_addr & PGSTE_ST2_MASK;
+       pgstes[2] |= (pgt_addr << 16) & PGSTE_ST2_MASK;
+       pgstes[3] |= (pgt_addr << 32) & PGSTE_ST2_MASK;
+}
+
 /**
  * gmap_shadow_pgt - instantiate a shadow page table
  * @sg: pointer to the shadow guest address space structure
@@ -1760,9 +1777,10 @@ int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
        ptdesc = page_table_alloc_pgste(sg->mm);
        if (!ptdesc)
                return -ENOMEM;
-       ptdesc->pt_index = pgt & _SEGMENT_ENTRY_ORIGIN;
+       origin = pgt & _SEGMENT_ENTRY_ORIGIN;
        if (fake)
-               ptdesc->pt_index |= GMAP_SHADOW_FAKE_TABLE;
+               origin |= GMAP_SHADOW_FAKE_TABLE;
+       gmap_pgste_set_pgt_addr(ptdesc, origin);
        s_pgt = page_to_phys(ptdesc_page(ptdesc));
        /* Install shadow page table */
        spin_lock(&sg->guest_table_lock);