Jan Beulich
2011-Mar-09 10:56 UTC
[Xen-devel] [PATCH 3/5] x86: make get_page_from_l1e() return a proper error code
... so that the guest can actually know the reason for the (hypercall)
failure.
ptwr_do_page_fault() could propagate the error indicator received from
get_page_from_l1e() back to the guest in the high half of the error
code (entry_vector), provided we''re sure all existing guests can deal
with that (or indicate so by means of a to-be-added guest feature
flag). Alternatively, a second virtual status register (like CR2) could
be introduced.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
--- 2011-03-09.orig/xen/arch/x86/mm.c
+++ 2011-03-09/xen/arch/x86/mm.c
@@ -799,12 +799,12 @@ get_page_from_l1e(
bool_t write;
if ( !(l1f & _PAGE_PRESENT) )
- return 1;
+ return 0;
if ( unlikely(l1f & l1_disallow_mask(l1e_owner)) )
{
MEM_LOG("Bad L1 flags %x", l1f &
l1_disallow_mask(l1e_owner));
- return 0;
+ return -EINVAL;
}
if ( !mfn_valid(mfn) ||
@@ -821,18 +821,21 @@ get_page_from_l1e(
if ( !iomem_access_permitted(pg_owner, mfn, mfn) )
{
if ( mfn != (PADDR_MASK >> PAGE_SHIFT) ) /* INVALID_MFN? */
+ {
MEM_LOG("Non-privileged (%u) attempt to map I/O space
%08lx",
pg_owner->domain_id, mfn);
- return 0;
+ return -EPERM;
+ }
+ return -EINVAL;
}
if ( !(l1f & _PAGE_RW) || IS_PRIV(pg_owner) ||
!rangeset_contains_singleton(mmio_ro_ranges, mfn) )
- return 1;
+ return 0;
dprintk(XENLOG_G_WARNING,
"d%d: Forcing read-only access to MFN %lx\n",
l1e_owner->domain_id, mfn);
- return -1;
+ return 1;
}
if ( unlikely(real_pg_owner != pg_owner) )
@@ -863,6 +866,7 @@ get_page_from_l1e(
{
unsigned long x, nx, y = page->count_info;
unsigned long cacheattr = pte_flags_to_cacheattr(l1f);
+ int err;
if ( is_xen_heap_page(page) )
{
@@ -870,7 +874,7 @@ get_page_from_l1e(
put_page_type(page);
put_page(page);
MEM_LOG("Attempt to change cache attributes of Xen heap
page");
- return 0;
+ return -EACCES;
}
do {
@@ -878,7 +882,8 @@ get_page_from_l1e(
nx = (x & ~PGC_cacheattr_mask) | (cacheattr <<
PGC_cacheattr_base);
} while ( (y = cmpxchg(&page->count_info, x, nx)) != x );
- if ( unlikely(update_xen_mappings(mfn, cacheattr) != 0) )
+ err = update_xen_mappings(mfn, cacheattr);
+ if ( unlikely(err) )
{
cacheattr = y & PGC_cacheattr_mask;
do {
@@ -894,11 +899,11 @@ get_page_from_l1e(
" from L1 entry %" PRIpte ") for %d",
mfn, get_gpfn_from_mfn(mfn),
l1e_get_intpte(l1e), l1e_owner->domain_id);
- return 0;
+ return err;
}
}
- return 1;
+ return 0;
could_not_pin:
MEM_LOG("Error getting mfn %lx (pfn %lx) from L1 entry %" PRIpte
@@ -907,7 +912,7 @@ get_page_from_l1e(
l1e_get_intpte(l1e), l1e_owner->domain_id,
pg_owner->domain_id);
if ( real_pg_owner != NULL )
put_page(page);
- return 0;
+ return -EBUSY;
}
@@ -1197,17 +1202,20 @@ static int alloc_l1_table(struct page_in
unsigned long pfn = page_to_mfn(page);
l1_pgentry_t *pl1e;
unsigned int i;
+ int ret = 0;
pl1e = map_domain_page(pfn);
for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
{
if ( is_guest_l1_slot(i) )
- switch ( get_page_from_l1e(pl1e[i], d, d) )
+ switch ( ret = get_page_from_l1e(pl1e[i], d, d) )
{
- case 0:
+ default:
goto fail;
- case -1:
+ case 0:
+ break;
+ case 1:
l1e_remove_flags(pl1e[i], _PAGE_RW);
break;
}
@@ -1225,7 +1233,7 @@ static int alloc_l1_table(struct page_in
put_page_from_l1e(pl1e[i], d);
unmap_domain_page(pl1e);
- return -EINVAL;
+ return ret;
}
static int create_pae_xen_mappings(struct domain *d, l3_pgentry_t *pl3e)
@@ -1794,11 +1802,13 @@ static int mod_l1_entry(l1_pgentry_t *pl
return rc;
}
- switch ( get_page_from_l1e(nl1e, pt_dom, pg_dom) )
+ switch ( rc = get_page_from_l1e(nl1e, pt_dom, pg_dom) )
{
- case 0:
+ default:
return 0;
- case -1:
+ case 0:
+ break;
+ case 1:
l1e_remove_flags(nl1e, _PAGE_RW);
break;
}
@@ -4948,7 +4958,7 @@ static int ptwr_emulated_update(
nl1e = l1e_from_intpte(val);
switch ( get_page_from_l1e(nl1e, d, d) )
{
- case 0:
+ default:
if ( is_pv_32bit_domain(d) && (bytes == 4) &&
(unaligned_addr & 4) &&
!do_cmpxchg && (l1e_get_flags(nl1e) & _PAGE_PRESENT) )
{
@@ -4968,7 +4978,9 @@ static int ptwr_emulated_update(
return X86EMUL_UNHANDLEABLE;
}
break;
- case -1:
+ case 0:
+ break;
+ case 1:
l1e_remove_flags(nl1e, _PAGE_RW);
break;
}
--- 2011-03-09.orig/xen/arch/x86/mm/shadow/multi.c
+++ 2011-03-09/xen/arch/x86/mm/shadow/multi.c
@@ -872,7 +872,7 @@ shadow_get_page_from_l1e(shadow_l1e_t sl
// If a privileged domain is attempting to install a map of a page it does
// not own, we let it succeed anyway.
//
- if ( unlikely(!res) &&
+ if ( unlikely(res < 0) &&
!shadow_mode_translate(d) &&
mfn_valid(mfn = shadow_l1e_get_mfn(sl1e)) &&
(owner = page_get_owner(mfn_to_page(mfn))) &&
@@ -883,11 +883,11 @@ shadow_get_page_from_l1e(shadow_l1e_t sl
SHADOW_PRINTK("privileged domain %d installs map of mfn %05lx
"
"which is owned by domain %d: %s\n",
d->domain_id, mfn_x(mfn), owner->domain_id,
- res ? "success" : "failed");
+ res >= 0 ? "success" : "failed");
}
/* Okay, it might still be a grant mapping PTE. Try it. */
- if ( unlikely(!res) &&
+ if ( unlikely(res < 0) &&
(type == p2m_grant_map_rw ||
(type == p2m_grant_map_ro &&
!(shadow_l1e_get_flags(sl1e) & _PAGE_RW))) )
@@ -900,7 +900,7 @@ shadow_get_page_from_l1e(shadow_l1e_t sl
res = get_page_from_l1e(sl1e, d, page_get_owner(mfn_to_page(mfn)));
}
- if ( unlikely(!res) )
+ if ( unlikely(res < 0) )
{
perfc_incr(shadow_get_page_fail);
SHADOW_PRINTK("failed: l1e=" SH_PRI_pte "\n");
@@ -1229,15 +1229,15 @@ static int shadow_set_l1e(struct vcpu *v
TRACE_SHADOW_PATH_FLAG(TRCE_SFLAG_SHADOW_L1_GET_REF);
switch ( shadow_get_page_from_l1e(new_sl1e, d, new_type) )
{
- case 0:
+ default:
/* Doesn''t look like a pagetable. */
flags |= SHADOW_SET_ERROR;
new_sl1e = shadow_l1e_empty();
break;
- case -1:
+ case 1:
shadow_l1e_remove_flags(new_sl1e, _PAGE_RW);
/* fall through */
- default:
+ case 0:
shadow_vram_get_l1e(new_sl1e, sl1e, sl1mfn, d);
break;
}
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