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x86/mm: switch to new APIs in map_pages_to_xen
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Page tables allocated in that function should be mapped and unmapped
now.

Take the opportunity to avoid a potential double map in
map_pages_to_xen() by initialising pl1e to NULL and only map it if it
was not mapped earlier.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
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@jbeulich
Wei Liu authored and jbeulich committed Apr 22, 2021
1 parent 4215992 commit 4b5b083
Showing 1 changed file with 38 additions and 26 deletions.
64 changes: 38 additions & 26 deletions xen/arch/x86/mm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5215,7 +5215,7 @@ int map_pages_to_xen(
}
else
{
l2_pgentry_t *l2t = l3e_to_l2e(ol3e);
l2_pgentry_t *l2t = map_l2t_from_l3e(ol3e);

for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
{
Expand All @@ -5227,10 +5227,11 @@ int map_pages_to_xen(
else
{
unsigned int j;
const l1_pgentry_t *l1t = l2e_to_l1e(ol2e);
const l1_pgentry_t *l1t = map_l1t_from_l2e(ol2e);

for ( j = 0; j < L1_PAGETABLE_ENTRIES; j++ )
flush_flags(l1e_get_flags(l1t[j]));
unmap_domain_page(l1t);
}
}
flush_area(virt, flush_flags);
Expand All @@ -5239,9 +5240,10 @@ int map_pages_to_xen(
ol2e = l2t[i];
if ( (l2e_get_flags(ol2e) & _PAGE_PRESENT) &&
!(l2e_get_flags(ol2e) & _PAGE_PSE) )
free_xen_pagetable(l2e_to_l1e(ol2e));
free_xen_pagetable_new(l2e_get_mfn(ol2e));
}
free_xen_pagetable(l2t);
unmap_domain_page(l2t);
free_xen_pagetable_new(l3e_get_mfn(ol3e));
}
}

Expand All @@ -5258,6 +5260,7 @@ int map_pages_to_xen(
unsigned int flush_flags =
FLUSH_TLB | FLUSH_ORDER(2 * PAGETABLE_ORDER);
l2_pgentry_t *l2t;
mfn_t l2mfn;

/* Skip this PTE if there is no change. */
if ( ((l3e_get_pfn(ol3e) & ~(L2_PAGETABLE_ENTRIES *
Expand All @@ -5279,15 +5282,17 @@ int map_pages_to_xen(
continue;
}

l2t = alloc_xen_pagetable();
if ( l2t == NULL )
l2mfn = alloc_xen_pagetable_new();
if ( mfn_eq(l2mfn, INVALID_MFN) )
goto out;

l2t = map_domain_page(l2mfn);
for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
l2e_write(l2t + i,
l2e_from_pfn(l3e_get_pfn(ol3e) +
(i << PAGETABLE_ORDER),
l3e_get_flags(ol3e)));
UNMAP_DOMAIN_PAGE(l2t);

if ( l3e_get_flags(ol3e) & _PAGE_GLOBAL )
flush_flags |= FLUSH_TLB_GLOBAL;
Expand All @@ -5297,15 +5302,15 @@ int map_pages_to_xen(
if ( (l3e_get_flags(*pl3e) & _PAGE_PRESENT) &&
(l3e_get_flags(*pl3e) & _PAGE_PSE) )
{
l3e_write_atomic(pl3e, l3e_from_mfn(virt_to_mfn(l2t),
__PAGE_HYPERVISOR));
l2t = NULL;
l3e_write_atomic(pl3e,
l3e_from_mfn(l2mfn, __PAGE_HYPERVISOR));
l2mfn = INVALID_MFN;
}
if ( locking )
spin_unlock(&map_pgdir_lock);
flush_area(virt, flush_flags);
if ( l2t )
free_xen_pagetable(l2t);

free_xen_pagetable_new(l2mfn);
}

pl2e = virt_to_xen_l2e(virt);
Expand Down Expand Up @@ -5333,12 +5338,13 @@ int map_pages_to_xen(
}
else
{
l1_pgentry_t *l1t = l2e_to_l1e(ol2e);
l1_pgentry_t *l1t = map_l1t_from_l2e(ol2e);

for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
flush_flags(l1e_get_flags(l1t[i]));
flush_area(virt, flush_flags);
free_xen_pagetable(l1t);
unmap_domain_page(l1t);
free_xen_pagetable_new(l2e_get_mfn(ol2e));
}
}

Expand All @@ -5349,20 +5355,20 @@ int map_pages_to_xen(
}
else
{
pl1e = NULL;
/* Normal page mapping. */
if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) )
{
pl1e = virt_to_xen_l1e(virt);
if ( pl1e == NULL )
goto out;

UNMAP_DOMAIN_PAGE(pl1e);
}
else if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
{
unsigned int flush_flags =
FLUSH_TLB | FLUSH_ORDER(PAGETABLE_ORDER);
l1_pgentry_t *l1t;
mfn_t l1mfn;

/* Skip this PTE if there is no change. */
if ( (((l2e_get_pfn(*pl2e) & ~(L1_PAGETABLE_ENTRIES - 1)) +
Expand All @@ -5382,14 +5388,16 @@ int map_pages_to_xen(
goto check_l3;
}

l1t = alloc_xen_pagetable();
if ( l1t == NULL )
l1mfn = alloc_xen_pagetable_new();
if ( mfn_eq(l1mfn, INVALID_MFN) )
goto out;

l1t = map_domain_page(l1mfn);
for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
l1e_write(&l1t[i],
l1e_from_pfn(l2e_get_pfn(*pl2e) + i,
lNf_to_l1f(l2e_get_flags(*pl2e))));
UNMAP_DOMAIN_PAGE(l1t);

if ( l2e_get_flags(*pl2e) & _PAGE_GLOBAL )
flush_flags |= FLUSH_TLB_GLOBAL;
Expand All @@ -5399,20 +5407,22 @@ int map_pages_to_xen(
if ( (l2e_get_flags(*pl2e) & _PAGE_PRESENT) &&
(l2e_get_flags(*pl2e) & _PAGE_PSE) )
{
l2e_write_atomic(pl2e, l2e_from_mfn(virt_to_mfn(l1t),
l2e_write_atomic(pl2e, l2e_from_mfn(l1mfn,
__PAGE_HYPERVISOR));
l1t = NULL;
l1mfn = INVALID_MFN;
}
if ( locking )
spin_unlock(&map_pgdir_lock);
flush_area(virt, flush_flags);
if ( l1t )
free_xen_pagetable(l1t);

free_xen_pagetable_new(l1mfn);
}

pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(virt);
if ( !pl1e )
pl1e = map_l1t_from_l2e(*pl2e) + l1_table_offset(virt);
ol1e = *pl1e;
l1e_write_atomic(pl1e, l1e_from_mfn(mfn, flags));
UNMAP_DOMAIN_PAGE(pl1e);
if ( (l1e_get_flags(ol1e) & _PAGE_PRESENT) )
{
unsigned int flush_flags = FLUSH_TLB | FLUSH_ORDER(0);
Expand Down Expand Up @@ -5456,12 +5466,13 @@ int map_pages_to_xen(
goto check_l3;
}

l1t = l2e_to_l1e(ol2e);
l1t = map_l1t_from_l2e(ol2e);
base_mfn = l1e_get_pfn(l1t[0]) & ~(L1_PAGETABLE_ENTRIES - 1);
for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
if ( (l1e_get_pfn(l1t[i]) != (base_mfn + i)) ||
(l1e_get_flags(l1t[i]) != flags) )
break;
UNMAP_DOMAIN_PAGE(l1t);
if ( i == L1_PAGETABLE_ENTRIES )
{
l2e_write_atomic(pl2e, l2e_from_pfn(base_mfn,
Expand All @@ -5471,7 +5482,7 @@ int map_pages_to_xen(
flush_area(virt - PAGE_SIZE,
FLUSH_TLB_GLOBAL |
FLUSH_ORDER(PAGETABLE_ORDER));
free_xen_pagetable(l2e_to_l1e(ol2e));
free_xen_pagetable_new(l2e_get_mfn(ol2e));
}
else if ( locking )
spin_unlock(&map_pgdir_lock);
Expand Down Expand Up @@ -5504,14 +5515,15 @@ int map_pages_to_xen(
continue;
}

l2t = l3e_to_l2e(ol3e);
l2t = map_l2t_from_l3e(ol3e);
base_mfn = l2e_get_pfn(l2t[0]) & ~(L2_PAGETABLE_ENTRIES *
L1_PAGETABLE_ENTRIES - 1);
for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
if ( (l2e_get_pfn(l2t[i]) !=
(base_mfn + (i << PAGETABLE_ORDER))) ||
(l2e_get_flags(l2t[i]) != l1f_to_lNf(flags)) )
break;
UNMAP_DOMAIN_PAGE(l2t);
if ( i == L2_PAGETABLE_ENTRIES )
{
l3e_write_atomic(pl3e, l3e_from_pfn(base_mfn,
Expand All @@ -5521,7 +5533,7 @@ int map_pages_to_xen(
flush_area(virt - PAGE_SIZE,
FLUSH_TLB_GLOBAL |
FLUSH_ORDER(2*PAGETABLE_ORDER));
free_xen_pagetable(l3e_to_l2e(ol3e));
free_xen_pagetable_new(l3e_get_mfn(ol3e));
}
else if ( locking )
spin_unlock(&map_pgdir_lock);
Expand Down

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