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x86/mm: rewrite virt_to_xen_l*e
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Rewrite those functions to use the new APIs. Modify its callers to unmap
the pointer returned. Since alloc_xen_pagetable_new() is almost never
useful unless accompanied by page clearing and a mapping, introduce a
helper alloc_map_clear_xen_pt() for this sequence.

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 1be65ec commit 4215992
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Showing 2 changed files with 72 additions and 31 deletions.
102 changes: 71 additions & 31 deletions xen/arch/x86/mm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4931,8 +4931,28 @@ void free_xen_pagetable_new(mfn_t mfn)
free_xenheap_page(mfn_to_virt(mfn_x(mfn)));
}

void *alloc_mapped_pagetable(mfn_t *pmfn)
{
mfn_t mfn = alloc_xen_pagetable_new();
void *ret;

if ( mfn_eq(mfn, INVALID_MFN) )
return NULL;

if ( pmfn )
*pmfn = mfn;
ret = map_domain_page(mfn);
clear_page(ret);

return ret;
}

static DEFINE_SPINLOCK(map_pgdir_lock);

/*
* For virt_to_xen_lXe() functions, they take a linear address and return a
* pointer to Xen's LX entry. Caller needs to unmap the pointer.
*/
static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
{
l4_pgentry_t *pl4e;
Expand All @@ -4941,33 +4961,33 @@ static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
{
bool locking = system_state > SYS_STATE_boot;
l3_pgentry_t *l3t = alloc_xen_pagetable();
mfn_t l3mfn;
l3_pgentry_t *l3t = alloc_mapped_pagetable(&l3mfn);

if ( !l3t )
return NULL;
clear_page(l3t);
UNMAP_DOMAIN_PAGE(l3t);
if ( locking )
spin_lock(&map_pgdir_lock);
if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
{
l4_pgentry_t l4e = l4e_from_paddr(__pa(l3t), __PAGE_HYPERVISOR);
l4_pgentry_t l4e = l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR);

l4e_write(pl4e, l4e);
efi_update_l4_pgtable(l4_table_offset(v), l4e);
l3t = NULL;
l3mfn = INVALID_MFN;
}
if ( locking )
spin_unlock(&map_pgdir_lock);
if ( l3t )
free_xen_pagetable(l3t);
free_xen_pagetable_new(l3mfn);
}

return l4e_to_l3e(*pl4e) + l3_table_offset(v);
return map_l3t_from_l4e(*pl4e) + l3_table_offset(v);
}

static l2_pgentry_t *virt_to_xen_l2e(unsigned long v)
{
l3_pgentry_t *pl3e;
l3_pgentry_t *pl3e, l3e;

pl3e = virt_to_xen_l3e(v);
if ( !pl3e )
Expand All @@ -4976,31 +4996,37 @@ static l2_pgentry_t *virt_to_xen_l2e(unsigned long v)
if ( !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) )
{
bool locking = system_state > SYS_STATE_boot;
l2_pgentry_t *l2t = alloc_xen_pagetable();
mfn_t l2mfn;
l2_pgentry_t *l2t = alloc_mapped_pagetable(&l2mfn);

if ( !l2t )
{
unmap_domain_page(pl3e);
return NULL;
clear_page(l2t);
}
UNMAP_DOMAIN_PAGE(l2t);
if ( locking )
spin_lock(&map_pgdir_lock);
if ( !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) )
{
l3e_write(pl3e, l3e_from_paddr(__pa(l2t), __PAGE_HYPERVISOR));
l2t = NULL;
l3e_write(pl3e, l3e_from_mfn(l2mfn, __PAGE_HYPERVISOR));
l2mfn = INVALID_MFN;
}
if ( locking )
spin_unlock(&map_pgdir_lock);
if ( l2t )
free_xen_pagetable(l2t);
free_xen_pagetable_new(l2mfn);
}

BUG_ON(l3e_get_flags(*pl3e) & _PAGE_PSE);
return l3e_to_l2e(*pl3e) + l2_table_offset(v);
l3e = *pl3e;
unmap_domain_page(pl3e);

return map_l2t_from_l3e(l3e) + l2_table_offset(v);
}

l1_pgentry_t *virt_to_xen_l1e(unsigned long v)
{
l2_pgentry_t *pl2e;
l2_pgentry_t *pl2e, l2e;

pl2e = virt_to_xen_l2e(v);
if ( !pl2e )
Expand All @@ -5009,26 +5035,32 @@ l1_pgentry_t *virt_to_xen_l1e(unsigned long v)
if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) )
{
bool locking = system_state > SYS_STATE_boot;
l1_pgentry_t *l1t = alloc_xen_pagetable();
mfn_t l1mfn;
l1_pgentry_t *l1t = alloc_mapped_pagetable(&l1mfn);

if ( !l1t )
{
unmap_domain_page(pl2e);
return NULL;
clear_page(l1t);
}
UNMAP_DOMAIN_PAGE(l1t);
if ( locking )
spin_lock(&map_pgdir_lock);
if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) )
{
l2e_write(pl2e, l2e_from_paddr(__pa(l1t), __PAGE_HYPERVISOR));
l1t = NULL;
l2e_write(pl2e, l2e_from_mfn(l1mfn, __PAGE_HYPERVISOR));
l1mfn = INVALID_MFN;
}
if ( locking )
spin_unlock(&map_pgdir_lock);
if ( l1t )
free_xen_pagetable(l1t);
free_xen_pagetable_new(l1mfn);
}

BUG_ON(l2e_get_flags(*pl2e) & _PAGE_PSE);
return l2e_to_l1e(*pl2e) + l1_table_offset(v);
l2e = *pl2e;
unmap_domain_page(pl2e);

return map_l1t_from_l2e(l2e) + l1_table_offset(v);
}

/* Convert to from superpage-mapping flags for map_pages_to_xen(). */
Expand Down Expand Up @@ -5085,7 +5117,7 @@ mfn_t xen_map_to_mfn(unsigned long va)

L3T_INIT(l3page);
CHECK_MAPPED(pl3e);
l3page = virt_to_page(pl3e);
l3page = mfn_to_page(domain_page_map_to_mfn(pl3e));
L3T_LOCK(l3page);

CHECK_MAPPED(l3e_get_flags(*pl3e) & _PAGE_PRESENT);
Expand Down Expand Up @@ -5124,7 +5156,8 @@ int map_pages_to_xen(
unsigned int flags)
{
bool locking = system_state > SYS_STATE_boot;
l2_pgentry_t *pl2e, ol2e;
l3_pgentry_t *pl3e = NULL, ol3e;
l2_pgentry_t *pl2e = NULL, ol2e;
l1_pgentry_t *pl1e, ol1e;
unsigned int i;
int rc = -ENOMEM;
Expand All @@ -5148,15 +5181,16 @@ int map_pages_to_xen(

while ( nr_mfns != 0 )
{
l3_pgentry_t *pl3e, ol3e;

/* Clean up the previous iteration. */
L3T_UNLOCK(current_l3page);
UNMAP_DOMAIN_PAGE(pl3e);
UNMAP_DOMAIN_PAGE(pl2e);

pl3e = virt_to_xen_l3e(virt);
if ( !pl3e )
goto out;

current_l3page = virt_to_page(pl3e);
current_l3page = mfn_to_page(domain_page_map_to_mfn(pl3e));
L3T_LOCK(current_l3page);
ol3e = *pl3e;

Expand Down Expand Up @@ -5321,6 +5355,8 @@ int map_pages_to_xen(
pl1e = virt_to_xen_l1e(virt);
if ( pl1e == NULL )
goto out;

UNMAP_DOMAIN_PAGE(pl1e);
}
else if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
{
Expand Down Expand Up @@ -5498,6 +5534,8 @@ int map_pages_to_xen(

out:
L3T_UNLOCK(current_l3page);
unmap_domain_page(pl3e);
unmap_domain_page(pl2e);
return rc;
}

Expand All @@ -5521,6 +5559,7 @@ int populate_pt_range(unsigned long virt, unsigned long nr_mfns)
int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
{
bool locking = system_state > SYS_STATE_boot;
l3_pgentry_t *pl3e = NULL;
l2_pgentry_t *pl2e;
l1_pgentry_t *pl1e;
unsigned int i;
Expand All @@ -5539,15 +5578,15 @@ int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)

while ( v < e )
{
l3_pgentry_t *pl3e;

/* Clean up the previous iteration. */
L3T_UNLOCK(current_l3page);
UNMAP_DOMAIN_PAGE(pl3e);

pl3e = virt_to_xen_l3e(v);
if ( !pl3e )
goto out;

current_l3page = virt_to_page(pl3e);
current_l3page = mfn_to_page(domain_page_map_to_mfn(pl3e));
L3T_LOCK(current_l3page);

if ( !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) )
Expand Down Expand Up @@ -5777,6 +5816,7 @@ int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)

out:
L3T_UNLOCK(current_l3page);
unmap_domain_page(pl3e);
return rc;
}

Expand Down
1 change: 1 addition & 0 deletions xen/include/asm-x86/mm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -577,6 +577,7 @@ void *alloc_xen_pagetable(void);
void free_xen_pagetable(void *v);
mfn_t alloc_xen_pagetable_new(void);
void free_xen_pagetable_new(mfn_t mfn);
void *alloc_mapped_pagetable(mfn_t *pmfn);

l1_pgentry_t *virt_to_xen_l1e(unsigned long v);

Expand Down

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