Commit 84b73876 authored by Claudio Imbrenda's avatar Claudio Imbrenda
Browse files

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: default avatarSteffen Eiden <seiden@linux.ibm.com>
Reviewed-by: default avatarChristoph Schlameuss <schlameuss@linux.ibm.com>
Link: https://lore.kernel.org/r/20250123144627.312456-16-imbrenda@linux.ibm.com


Signed-off-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20250123144627.312456-16-imbrenda@linux.ibm.com>
parent 1f438993

arch/s390/include/asm/pgtable.h

+15 −0
Original line number Diff line number Diff line
@@ -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 */

arch/s390/kvm/gaccess.c

+4 −2
Original line number Diff line number Diff line
@@ -1409,6 +1409,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr, 
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;

arch/s390/mm/gmap.c

+20 −2
Original line number Diff line number Diff line
@@ -1733,6 +1733,23 @@ int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt, 
}

EXPORT_SYMBOL_GPL(gmap_shadow_sgt);



static void gmap_pgste_set_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);