[PATCH v2 15/15] KVM: s390: remove the last user of page->index

Claudio Imbrenda
2025-01-16T11:34:15Z

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.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
arch/s390/include/asm/pgtable.h | 15 +++++++++++++++
arch/s390/kvm/gaccess.c | 6 ++++--
arch/s390/mm/gmap.c | 22 ++++++++++++++++++++--
3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 151488bb9ed7..948100a8fa7e 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -419,6 +419,7 @@ static inline int is_module_addr(void *addr)
#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 */
@@ -2001,4 +2002,18 @@ 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_index(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 560b5677929b..3bf3a80942de 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1409,6 +1409,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
static int gmap_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 gmap_shadow_pgt_lookup(struct gmap *sg, unsigned long saddr, unsigned
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_index(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 80674bbf0f7b..dd06dbecc0a0 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -1720,6 +1720,23 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
}
EXPORT_SYMBOL_GPL(gmap_shadow_sgt);

+static void gmap_pgste_set_index(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
@@ -1747,9 +1764,10 @@ 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_index(ptdesc, origin);
s_pgt = page_to_phys(ptdesc_page(ptdesc));
/* Install shadow page table */
spin_lock(&sg->guest_table_lock);
--
2.47.1