Re: [Xen-devel] [PATCH v3 2/3] x86/p2m: make p2m_alloc_ptp() return an MFN

[Tian, Kevin]

> From: Jan Beulich [mailto:jbeul...@suse.com]
> Sent: Friday, August 11, 2017 9:20 PM
> 
> None of the callers really needs the struct page_info pointer.
> 
> Signed-off-by: Jan Beulich 
> Acked-by: George Dunlap 

Reviewed-by: Kevin Tian 

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[Xen-devel] [PATCH v3 2/3] x86/p2m: make p2m_alloc_ptp() return an MFN

[Jan Beulich]

None of the callers really needs the struct page_info pointer.

Signed-off-by: Jan Beulich 
Acked-by: George Dunlap 
---
v3: Re-base over changes to patch 1.
v2: Re-base over changes to patch 1.

--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -569,7 +569,7 @@ int p2m_set_entry(struct p2m_domain *p2m
 return rc;
 }
 
-struct page_info *p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type)
+mfn_t p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type)
 {
 struct page_info *pg;
 
@@ -577,13 +577,13 @@ struct page_info *p2m_alloc_ptp(struct p
 ASSERT(p2m->domain);
 ASSERT(p2m->domain->arch.paging.alloc_page);
 pg = p2m->domain->arch.paging.alloc_page(p2m->domain);
-if (pg == NULL)
-return NULL;
+if ( !pg )
+return INVALID_MFN;
 
 page_list_add_tail(pg, >pages);
 pg->u.inuse.type_info = type | 1 | PGT_validated;
 
-return pg;
+return page_to_mfn(pg);
 }
 
 void p2m_free_ptp(struct p2m_domain *p2m, struct page_info *pg)
@@ -609,7 +609,7 @@ void p2m_free_ptp(struct p2m_domain *p2m
  */
 int p2m_alloc_table(struct p2m_domain *p2m)
 {
-struct page_info *p2m_top;
+mfn_t top_mfn;
 struct domain *d = p2m->domain;
 int rc = 0;
 
@@ -632,14 +632,14 @@ int p2m_alloc_table(struct p2m_domain *p
 
 P2M_PRINTK("allocating p2m table\n");
 
-p2m_top = p2m_alloc_ptp(p2m, PGT_l4_page_table);
-if ( p2m_top == NULL )
+top_mfn = p2m_alloc_ptp(p2m, PGT_l4_page_table);
+if ( mfn_eq(top_mfn, INVALID_MFN) )
 {
 p2m_unlock(p2m);
 return -ENOMEM;
 }
 
-p2m->phys_table = pagetable_from_mfn(page_to_mfn(p2m_top));
+p2m->phys_table = pagetable_from_mfn(top_mfn);
 
 if ( hap_enabled(d) )
 iommu_share_p2m_table(d);
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -225,16 +225,16 @@ static void ept_p2m_type_to_flags(struct
 /* Fill in middle levels of ept table */
 static int ept_set_middle_entry(struct p2m_domain *p2m, ept_entry_t *ept_entry)
 {
-struct page_info *pg;
+mfn_t mfn;
 ept_entry_t *table;
 unsigned int i;
 
-pg = p2m_alloc_ptp(p2m, 0);
-if ( pg == NULL )
+mfn = p2m_alloc_ptp(p2m, 0);
+if ( mfn_eq(mfn, INVALID_MFN) )
 return 0;
 
 ept_entry->epte = 0;
-ept_entry->mfn = page_to_mfn(pg);
+ept_entry->mfn = mfn_x(mfn);
 ept_entry->access = p2m->default_access;
 
 ept_entry->r = ept_entry->w = ept_entry->x = 1;
@@ -243,7 +243,7 @@ static int ept_set_middle_entry(struct p
 
 ept_entry->suppress_ve = 1;
 
-table = __map_domain_page(pg);
+table = map_domain_page(mfn);
 
 for ( i = 0; i < EPT_PAGETABLE_ENTRIES; i++ )
 table[i].suppress_ve = 1;
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -204,14 +204,12 @@ p2m_next_level(struct p2m_domain *p2m, v
 /* PoD/paging: Not present doesn't imply empty. */
 if ( !flags )
 {
-struct page_info *pg;
+mfn_t mfn = p2m_alloc_ptp(p2m, type);
 
-pg = p2m_alloc_ptp(p2m, type);
-if ( pg == NULL )
+if ( mfn_eq(mfn, INVALID_MFN) )
 return -ENOMEM;
 
-new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
- P2M_BASE_FLAGS | _PAGE_RW);
+new_entry = l1e_from_pfn(mfn_x(mfn), P2M_BASE_FLAGS | _PAGE_RW);
 
 switch ( type ) {
 case PGT_l3_page_table:
@@ -235,7 +233,7 @@ p2m_next_level(struct p2m_domain *p2m, v
 {
 /* Split superpages pages into smaller ones. */
 unsigned long pfn = l1e_get_pfn(*p2m_entry);
-struct page_info *pg;
+mfn_t mfn;
 l1_pgentry_t *l1_entry;
 unsigned int i, level;
 
@@ -263,11 +261,11 @@ p2m_next_level(struct p2m_domain *p2m, v
 return -EINVAL;
 }
 
-pg = p2m_alloc_ptp(p2m, type);
-if ( pg == NULL )
+mfn = p2m_alloc_ptp(p2m, type);
+if ( mfn_eq(mfn, INVALID_MFN) )
 return -ENOMEM;
 
-l1_entry = __map_domain_page(pg);
+l1_entry = map_domain_page(mfn);
 
 /* Inherit original IOMMU permissions, but update Next Level. */
 if ( iommu_hap_pt_share )
@@ -285,8 +283,7 @@ p2m_next_level(struct p2m_domain *p2m, v
 
 unmap_domain_page(l1_entry);
 
-new_entry = l1e_from_pfn(mfn_x(page_to_mfn(pg)),
- P2M_BASE_FLAGS | _PAGE_RW);
+new_entry = l1e_from_pfn(mfn_x(mfn), P2M_BASE_FLAGS | _PAGE_RW);
 p2m_add_iommu_flags(_entry, level, 
IOMMUF_readable|IOMMUF_writable);
 p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, level + 1);
 }
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -684,7 +684,7 @@ void p2m_mem_paging_resume(struct domain
  * Internal functions, only called by other p2m code
  */
 
-struct page_info *p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long type);
+mfn_t p2m_alloc_ptp(struct p2m_domain *p2m, unsigned long