>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 02.07.09 09:37 >>>
>On 02/07/2009 08:23, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>
>> Am I right in understanding that the restriction on 512 entries to be passed
>> in is solely to cap the time that's being spent in the hypervisor without
>> being
>> able to service softirq requests as well as while the domain lock is being
>> held?
>> If that's the case, eliminating that restriction could be fairly strait
>> forward by
>> putting the majority of the function body in a loop or, perhaps even better,
>> calling hypercall_preempt_check() every so many entries and using the
>> continuation mechanism.
>
>Yes, true.
Would you have time to look over this (so far only compile tested) patch,
to see if there's anything obviously wrong (I admit I feel uncertain
whenever it comes to touching the grant table code)?
Thanks, Jan
--- 2009-06-10.orig/xen/common/compat/grant_table.c 2008-08-01
08:48:42.000000000 +0200
+++ 2009-06-10/xen/common/compat/grant_table.c 2009-07-02 14:42:05.000000000
+0200
@@ -35,7 +35,9 @@ int compat_grant_table_op(unsigned int c
{
int rc = 0;
unsigned int i;
+ XEN_GUEST_HANDLE(void) cnt_uop;
+ set_xen_guest_handle(cnt_uop, NULL);
switch ( cmd )
{
#define CASE(name) \
@@ -79,7 +81,7 @@ int compat_grant_table_op(unsigned int c
return do_grant_table_op(cmd, cmp_uop, count);
}
- if ( count > 512 )
+ if ( (int)count < 0 )
rc = -EINVAL;
for ( i = 0; i < count && rc == 0; )
@@ -128,6 +130,7 @@ int compat_grant_table_op(unsigned int c
rc = gnttab_setup_table(guest_handle_cast(nat.uop,
gnttab_setup_table_t), 1);
}
}
+ ASSERT(rc <= 0);
if ( rc == 0 )
{
#define XLAT_gnttab_setup_table_HNDL_frame_list(_d_, _s_) \
@@ -163,12 +166,19 @@ int compat_grant_table_op(unsigned int c
}
if ( rc == 0 )
rc = gnttab_transfer(guest_handle_cast(nat.uop,
gnttab_transfer_t), n);
- if ( rc == 0 )
+ if ( rc > 0 )
+ {
+ ASSERT(rc < n);
+ i -= n - rc;
+ n = rc;
+ }
+ if ( rc >= 0 )
{
XEN_GUEST_HANDLE(gnttab_transfer_compat_t) xfer;
xfer = guest_handle_cast(cmp_uop, gnttab_transfer_compat_t);
guest_handle_add_offset(xfer, i);
+ cnt_uop = guest_handle_cast(xfer, void);
while ( n-- )
{
guest_handle_add_offset(xfer, -1);
@@ -201,12 +211,19 @@ int compat_grant_table_op(unsigned int c
}
if ( rc == 0 )
rc = gnttab_copy(guest_handle_cast(nat.uop, gnttab_copy_t), n);
- if ( rc == 0 )
+ if ( rc > 0 )
+ {
+ ASSERT(rc < n);
+ i -= n - rc;
+ n = rc;
+ }
+ if ( rc >= 0 )
{
XEN_GUEST_HANDLE(gnttab_copy_compat_t) copy;
copy = guest_handle_cast(cmp_uop, gnttab_copy_compat_t);
guest_handle_add_offset(copy, i);
+ cnt_uop = guest_handle_cast(copy, void);
while ( n-- )
{
guest_handle_add_offset(copy, -1);
@@ -222,6 +239,14 @@ int compat_grant_table_op(unsigned int c
}
}
+ if ( rc > 0 )
+ {
+ ASSERT(i < count);
+ ASSERT(!guest_handle_is_null(cnt_uop));
+ rc = hypercall_create_continuation(__HYPERVISOR_grant_table_op,
+ "ihi", cmd, cnt_uop, count - i);
+ }
+
return rc;
}
--- 2009-06-10.orig/xen/common/grant_table.c 2009-06-03 12:22:45.000000000
+0200
+++ 2009-06-10/xen/common/grant_table.c 2009-07-02 14:42:33.000000000 +0200
@@ -29,6 +29,7 @@
#include <xen/lib.h>
#include <xen/sched.h>
#include <xen/mm.h>
+#include <xen/event.h>
#include <xen/trace.h>
#include <xen/guest_access.h>
#include <xen/domain_page.h>
@@ -465,6 +466,8 @@ gnttab_map_grant_ref(
for ( i = 0; i < count; i++ )
{
+ if (i && hypercall_preempt_check())
+ return i;
if ( unlikely(__copy_from_guest_offset(&op, uop, i, 1)) )
return -EFAULT;
__gnttab_map_grant_ref(&op);
@@ -722,6 +725,9 @@ gnttab_unmap_grant_ref(
count -= c;
done += c;
+
+ if (count && hypercall_preempt_check())
+ return done;
}
return 0;
@@ -781,6 +787,9 @@ gnttab_unmap_and_replace(
count -= c;
done += c;
+
+ if (count && hypercall_preempt_check())
+ return done;
}
return 0;
@@ -1086,6 +1095,9 @@ gnttab_transfer(
for ( i = 0; i < count; i++ )
{
+ if (i && hypercall_preempt_check())
+ return i;
+
/* Read from caller address space. */
if ( unlikely(__copy_from_guest_offset(&gop, uop, i, 1)) )
{
@@ -1478,6 +1490,8 @@ gnttab_copy(
for ( i = 0; i < count; i++ )
{
+ if (i && hypercall_preempt_check())
+ return i;
if ( unlikely(__copy_from_guest_offset(&op, uop, i, 1)) )
return -EFAULT;
__gnttab_copy(&op);
@@ -1494,7 +1508,7 @@ do_grant_table_op(
long rc;
struct domain *d = current->domain;
- if ( count > 512 )
+ if ( (int)count < 0 )
return -EINVAL;
domain_lock(d);
@@ -1509,6 +1523,11 @@ do_grant_table_op(
if ( unlikely(!guest_handle_okay(map, count)) )
goto out;
rc = gnttab_map_grant_ref(map, count);
+ if ( rc > 0 )
+ {
+ guest_handle_add_offset(map, rc);
+ uop = guest_handle_cast(map, void);
+ }
break;
}
case GNTTABOP_unmap_grant_ref:
@@ -1518,6 +1537,11 @@ do_grant_table_op(
if ( unlikely(!guest_handle_okay(unmap, count)) )
goto out;
rc = gnttab_unmap_grant_ref(unmap, count);
+ if ( rc > 0 )
+ {
+ guest_handle_add_offset(unmap, rc);
+ uop = guest_handle_cast(unmap, void);
+ }
break;
}
case GNTTABOP_unmap_and_replace:
@@ -1530,12 +1554,18 @@ do_grant_table_op(
if ( unlikely(!replace_grant_supported()) )
goto out;
rc = gnttab_unmap_and_replace(unmap, count);
+ if ( rc > 0 )
+ {
+ guest_handle_add_offset(unmap, rc);
+ uop = guest_handle_cast(unmap, void);
+ }
break;
}
case GNTTABOP_setup_table:
{
rc = gnttab_setup_table(
guest_handle_cast(uop, gnttab_setup_table_t), count);
+ ASSERT(rc <= 0);
break;
}
case GNTTABOP_transfer:
@@ -1545,6 +1575,11 @@ do_grant_table_op(
if ( unlikely(!guest_handle_okay(transfer, count)) )
goto out;
rc = gnttab_transfer(transfer, count);
+ if ( rc > 0 )
+ {
+ guest_handle_add_offset(transfer, rc);
+ uop = guest_handle_cast(transfer, void);
+ }
break;
}
case GNTTABOP_copy:
@@ -1554,12 +1589,18 @@ do_grant_table_op(
if ( unlikely(!guest_handle_okay(copy, count)) )
goto out;
rc = gnttab_copy(copy, count);
+ if ( rc > 0 )
+ {
+ guest_handle_add_offset(copy, rc);
+ uop = guest_handle_cast(copy, void);
+ }
break;
}
case GNTTABOP_query_size:
{
rc = gnttab_query_size(
guest_handle_cast(uop, gnttab_query_size_t), count);
+ ASSERT(rc <= 0);
break;
}
default:
@@ -1569,6 +1610,13 @@ do_grant_table_op(
out:
domain_unlock(d);
+
+ if ( rc > 0 )
+ {
+ ASSERT(rc < count);
+ rc = hypercall_create_continuation(__HYPERVISOR_grant_table_op,
+ "ihi", cmd, uop, count - rc);
+ }
return rc;
}
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