* [PATCH] x86/paging: use clear_guest() for zero-filling guest buffers
@ 2012-02-06 16:35 Jan Beulich
2012-02-13 11:32 ` Ping: " Jan Beulich
0 siblings, 1 reply; 3+ messages in thread
From: Jan Beulich @ 2012-02-06 16:35 UTC (permalink / raw)
To: xen-devel@lists.xensource.com
[-- Attachment #1: Type: text/plain, Size: 5106 bytes --]
While static arrays of all zeros may be tolerable (but are simply
inefficient now that we have the necessary infrastructure), using on-
stack arrays for this purpose (particularly when their size doesn't
have an upper limit enforced) is calling for eventual problems (even
if the code can be reached via administrative interfaces only).
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -21,11 +21,11 @@
*/
#include <xen/init.h>
+#include <xen/guest_access.h>
#include <asm/paging.h>
#include <asm/shadow.h>
#include <asm/p2m.h>
#include <asm/hap.h>
-#include <asm/guest_access.h>
#include <asm/hvm/nestedhvm.h>
#include <xen/numa.h>
#include <xsm/xsm.h>
@@ -383,26 +383,30 @@ int paging_log_dirty_op(struct domain *d
(pages < sc->pages) && (i2 < LOGDIRTY_NODE_ENTRIES);
i2++ )
{
- static unsigned long zeroes[PAGE_SIZE/BYTES_PER_LONG];
unsigned int bytes = PAGE_SIZE;
l1 = ((l2 && mfn_valid(l2[i2])) ?
- map_domain_page(mfn_x(l2[i2])) : zeroes);
+ map_domain_page(mfn_x(l2[i2])) : NULL);
if ( unlikely(((sc->pages - pages + 7) >> 3) < bytes) )
bytes = (unsigned int)((sc->pages - pages + 7) >> 3);
if ( likely(peek) )
{
- if ( copy_to_guest_offset(sc->dirty_bitmap, pages >> 3,
- (uint8_t *)l1, bytes) != 0 )
+ if ( (l1 ? copy_to_guest_offset(sc->dirty_bitmap,
+ pages >> 3, (uint8_t *)l1,
+ bytes)
+ : clear_guest_offset(sc->dirty_bitmap,
+ pages >> 3, bytes)) != 0 )
{
rv = -EFAULT;
goto out;
}
}
- if ( clean && l1 != zeroes )
- clear_page(l1);
pages += bytes << 3;
- if ( l1 != zeroes )
+ if ( l1 )
+ {
+ if ( clean )
+ clear_page(l1);
unmap_domain_page(l1);
+ }
}
if ( l2 )
unmap_domain_page(l2);
@@ -462,12 +466,9 @@ int paging_log_dirty_range(struct domain
if ( !d->arch.paging.log_dirty.fault_count &&
!d->arch.paging.log_dirty.dirty_count ) {
- int size = (nr + BITS_PER_LONG - 1) / BITS_PER_LONG;
- unsigned long zeroes[size];
- memset(zeroes, 0x00, size * BYTES_PER_LONG);
- rv = 0;
- if ( copy_to_guest_offset(dirty_bitmap, 0, (uint8_t *) zeroes,
- size * BYTES_PER_LONG) != 0 )
+ unsigned int size = BITS_TO_LONGS(nr);
+
+ if ( clear_guest(dirty_bitmap, size * BYTES_PER_LONG) != 0 )
rv = -EFAULT;
goto out;
}
@@ -495,11 +496,10 @@ int paging_log_dirty_range(struct domain
(pages < nr) && (i2 < LOGDIRTY_NODE_ENTRIES);
i2++ )
{
- static unsigned long zeroes[PAGE_SIZE/BYTES_PER_LONG];
unsigned int bytes = PAGE_SIZE;
uint8_t *s;
l1 = ((l2 && mfn_valid(l2[i2])) ?
- map_domain_page(mfn_x(l2[i2])) : zeroes);
+ map_domain_page(mfn_x(l2[i2])) : NULL);
s = ((uint8_t*)l1) + (b1 >> 3);
bytes -= b1 >> 3;
@@ -507,9 +507,18 @@ int paging_log_dirty_range(struct domain
if ( likely(((nr - pages + 7) >> 3) < bytes) )
bytes = (unsigned int)((nr - pages + 7) >> 3);
+ if ( !l1 )
+ {
+ if ( clear_guest_offset(dirty_bitmap, pages >> 3,
+ bytes) != 0 )
+ {
+ rv = -EFAULT;
+ goto out;
+ }
+ }
/* begin_pfn is not 32K aligned, hence we have to bit
* shift the bitmap */
- if ( b1 & 0x7 )
+ else if ( b1 & 0x7 )
{
int i, j;
uint32_t *l = (uint32_t*) s;
@@ -553,11 +562,12 @@ int paging_log_dirty_range(struct domain
}
}
- if ( l1 != zeroes )
- clear_page(l1);
pages += bytes << 3;
- if ( l1 != zeroes )
+ if ( l1 )
+ {
+ clear_page(l1);
unmap_domain_page(l1);
+ }
b1 = b1 & 0x7;
}
b2 = 0;
[-- Attachment #2: x86-paging-use-clear_guest.patch --]
[-- Type: text/plain, Size: 5166 bytes --]
x86/paging: use clear_guest() for zero-filling guest buffers
While static arrays of all zeros may be tolerable (but are simply
inefficient now that we have the necessary infrastructure), using on-
stack arrays for this purpose (particularly when their size doesn't
have an upper limit enforced) is calling for eventual problems (even
if the code can be reached via administrative interfaces only).
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -21,11 +21,11 @@
*/
#include <xen/init.h>
+#include <xen/guest_access.h>
#include <asm/paging.h>
#include <asm/shadow.h>
#include <asm/p2m.h>
#include <asm/hap.h>
-#include <asm/guest_access.h>
#include <asm/hvm/nestedhvm.h>
#include <xen/numa.h>
#include <xsm/xsm.h>
@@ -383,26 +383,30 @@ int paging_log_dirty_op(struct domain *d
(pages < sc->pages) && (i2 < LOGDIRTY_NODE_ENTRIES);
i2++ )
{
- static unsigned long zeroes[PAGE_SIZE/BYTES_PER_LONG];
unsigned int bytes = PAGE_SIZE;
l1 = ((l2 && mfn_valid(l2[i2])) ?
- map_domain_page(mfn_x(l2[i2])) : zeroes);
+ map_domain_page(mfn_x(l2[i2])) : NULL);
if ( unlikely(((sc->pages - pages + 7) >> 3) < bytes) )
bytes = (unsigned int)((sc->pages - pages + 7) >> 3);
if ( likely(peek) )
{
- if ( copy_to_guest_offset(sc->dirty_bitmap, pages >> 3,
- (uint8_t *)l1, bytes) != 0 )
+ if ( (l1 ? copy_to_guest_offset(sc->dirty_bitmap,
+ pages >> 3, (uint8_t *)l1,
+ bytes)
+ : clear_guest_offset(sc->dirty_bitmap,
+ pages >> 3, bytes)) != 0 )
{
rv = -EFAULT;
goto out;
}
}
- if ( clean && l1 != zeroes )
- clear_page(l1);
pages += bytes << 3;
- if ( l1 != zeroes )
+ if ( l1 )
+ {
+ if ( clean )
+ clear_page(l1);
unmap_domain_page(l1);
+ }
}
if ( l2 )
unmap_domain_page(l2);
@@ -462,12 +466,9 @@ int paging_log_dirty_range(struct domain
if ( !d->arch.paging.log_dirty.fault_count &&
!d->arch.paging.log_dirty.dirty_count ) {
- int size = (nr + BITS_PER_LONG - 1) / BITS_PER_LONG;
- unsigned long zeroes[size];
- memset(zeroes, 0x00, size * BYTES_PER_LONG);
- rv = 0;
- if ( copy_to_guest_offset(dirty_bitmap, 0, (uint8_t *) zeroes,
- size * BYTES_PER_LONG) != 0 )
+ unsigned int size = BITS_TO_LONGS(nr);
+
+ if ( clear_guest(dirty_bitmap, size * BYTES_PER_LONG) != 0 )
rv = -EFAULT;
goto out;
}
@@ -495,11 +496,10 @@ int paging_log_dirty_range(struct domain
(pages < nr) && (i2 < LOGDIRTY_NODE_ENTRIES);
i2++ )
{
- static unsigned long zeroes[PAGE_SIZE/BYTES_PER_LONG];
unsigned int bytes = PAGE_SIZE;
uint8_t *s;
l1 = ((l2 && mfn_valid(l2[i2])) ?
- map_domain_page(mfn_x(l2[i2])) : zeroes);
+ map_domain_page(mfn_x(l2[i2])) : NULL);
s = ((uint8_t*)l1) + (b1 >> 3);
bytes -= b1 >> 3;
@@ -507,9 +507,18 @@ int paging_log_dirty_range(struct domain
if ( likely(((nr - pages + 7) >> 3) < bytes) )
bytes = (unsigned int)((nr - pages + 7) >> 3);
+ if ( !l1 )
+ {
+ if ( clear_guest_offset(dirty_bitmap, pages >> 3,
+ bytes) != 0 )
+ {
+ rv = -EFAULT;
+ goto out;
+ }
+ }
/* begin_pfn is not 32K aligned, hence we have to bit
* shift the bitmap */
- if ( b1 & 0x7 )
+ else if ( b1 & 0x7 )
{
int i, j;
uint32_t *l = (uint32_t*) s;
@@ -553,11 +562,12 @@ int paging_log_dirty_range(struct domain
}
}
- if ( l1 != zeroes )
- clear_page(l1);
pages += bytes << 3;
- if ( l1 != zeroes )
+ if ( l1 )
+ {
+ clear_page(l1);
unmap_domain_page(l1);
+ }
b1 = b1 & 0x7;
}
b2 = 0;
[-- Attachment #3: Type: text/plain, Size: 138 bytes --]
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^ permalink raw reply [flat|nested] 3+ messages in thread* Ping: [PATCH] x86/paging: use clear_guest() for zero-filling guest buffers
2012-02-06 16:35 [PATCH] x86/paging: use clear_guest() for zero-filling guest buffers Jan Beulich
@ 2012-02-13 11:32 ` Jan Beulich
2012-02-13 11:41 ` Tim Deegan
0 siblings, 1 reply; 3+ messages in thread
From: Jan Beulich @ 2012-02-13 11:32 UTC (permalink / raw)
To: Tim Deegan; +Cc: xen-devel@lists.xensource.com
>>> On 06.02.12 at 17:35, "Jan Beulich" <JBeulich@suse.com> wrote:
> While static arrays of all zeros may be tolerable (but are simply
> inefficient now that we have the necessary infrastructure), using on-
> stack arrays for this purpose (particularly when their size doesn't
> have an upper limit enforced) is calling for eventual problems (even
> if the code can be reached via administrative interfaces only).
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/mm/paging.c
> +++ b/xen/arch/x86/mm/paging.c
> @@ -21,11 +21,11 @@
> */
>
> #include <xen/init.h>
> +#include <xen/guest_access.h>
> #include <asm/paging.h>
> #include <asm/shadow.h>
> #include <asm/p2m.h>
> #include <asm/hap.h>
> -#include <asm/guest_access.h>
> #include <asm/hvm/nestedhvm.h>
> #include <xen/numa.h>
> #include <xsm/xsm.h>
> @@ -383,26 +383,30 @@ int paging_log_dirty_op(struct domain *d
> (pages < sc->pages) && (i2 < LOGDIRTY_NODE_ENTRIES);
> i2++ )
> {
> - static unsigned long zeroes[PAGE_SIZE/BYTES_PER_LONG];
> unsigned int bytes = PAGE_SIZE;
> l1 = ((l2 && mfn_valid(l2[i2])) ?
> - map_domain_page(mfn_x(l2[i2])) : zeroes);
> + map_domain_page(mfn_x(l2[i2])) : NULL);
> if ( unlikely(((sc->pages - pages + 7) >> 3) < bytes) )
> bytes = (unsigned int)((sc->pages - pages + 7) >> 3);
> if ( likely(peek) )
> {
> - if ( copy_to_guest_offset(sc->dirty_bitmap, pages >> 3,
> - (uint8_t *)l1, bytes) != 0 )
> + if ( (l1 ? copy_to_guest_offset(sc->dirty_bitmap,
> + pages >> 3, (uint8_t
> *)l1,
> + bytes)
> + : clear_guest_offset(sc->dirty_bitmap,
> + pages >> 3, bytes)) != 0 )
> {
> rv = -EFAULT;
> goto out;
> }
> }
> - if ( clean && l1 != zeroes )
> - clear_page(l1);
> pages += bytes << 3;
> - if ( l1 != zeroes )
> + if ( l1 )
> + {
> + if ( clean )
> + clear_page(l1);
> unmap_domain_page(l1);
> + }
> }
> if ( l2 )
> unmap_domain_page(l2);
> @@ -462,12 +466,9 @@ int paging_log_dirty_range(struct domain
>
> if ( !d->arch.paging.log_dirty.fault_count &&
> !d->arch.paging.log_dirty.dirty_count ) {
> - int size = (nr + BITS_PER_LONG - 1) / BITS_PER_LONG;
> - unsigned long zeroes[size];
> - memset(zeroes, 0x00, size * BYTES_PER_LONG);
> - rv = 0;
> - if ( copy_to_guest_offset(dirty_bitmap, 0, (uint8_t *) zeroes,
> - size * BYTES_PER_LONG) != 0 )
> + unsigned int size = BITS_TO_LONGS(nr);
> +
> + if ( clear_guest(dirty_bitmap, size * BYTES_PER_LONG) != 0 )
> rv = -EFAULT;
> goto out;
> }
> @@ -495,11 +496,10 @@ int paging_log_dirty_range(struct domain
> (pages < nr) && (i2 < LOGDIRTY_NODE_ENTRIES);
> i2++ )
> {
> - static unsigned long zeroes[PAGE_SIZE/BYTES_PER_LONG];
> unsigned int bytes = PAGE_SIZE;
> uint8_t *s;
> l1 = ((l2 && mfn_valid(l2[i2])) ?
> - map_domain_page(mfn_x(l2[i2])) : zeroes);
> + map_domain_page(mfn_x(l2[i2])) : NULL);
>
> s = ((uint8_t*)l1) + (b1 >> 3);
> bytes -= b1 >> 3;
> @@ -507,9 +507,18 @@ int paging_log_dirty_range(struct domain
> if ( likely(((nr - pages + 7) >> 3) < bytes) )
> bytes = (unsigned int)((nr - pages + 7) >> 3);
>
> + if ( !l1 )
> + {
> + if ( clear_guest_offset(dirty_bitmap, pages >> 3,
> + bytes) != 0 )
> + {
> + rv = -EFAULT;
> + goto out;
> + }
> + }
> /* begin_pfn is not 32K aligned, hence we have to bit
> * shift the bitmap */
> - if ( b1 & 0x7 )
> + else if ( b1 & 0x7 )
> {
> int i, j;
> uint32_t *l = (uint32_t*) s;
> @@ -553,11 +562,12 @@ int paging_log_dirty_range(struct domain
> }
> }
>
> - if ( l1 != zeroes )
> - clear_page(l1);
> pages += bytes << 3;
> - if ( l1 != zeroes )
> + if ( l1 )
> + {
> + clear_page(l1);
> unmap_domain_page(l1);
> + }
> b1 = b1 & 0x7;
> }
> b2 = 0;
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: Ping: [PATCH] x86/paging: use clear_guest() for zero-filling guest buffers
2012-02-13 11:32 ` Ping: " Jan Beulich
@ 2012-02-13 11:41 ` Tim Deegan
0 siblings, 0 replies; 3+ messages in thread
From: Tim Deegan @ 2012-02-13 11:41 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel@lists.xensource.com
At 11:32 +0000 on 13 Feb (1329132733), Jan Beulich wrote:
> >>> On 06.02.12 at 17:35, "Jan Beulich" <JBeulich@suse.com> wrote:
> > While static arrays of all zeros may be tolerable (but are simply
> > inefficient now that we have the necessary infrastructure), using on-
> > stack arrays for this purpose (particularly when their size doesn't
> > have an upper limit enforced) is calling for eventual problems (even
> > if the code can be reached via administrative interfaces only).
> >
> > Signed-off-by: Jan Beulich <jbeulich@suse.com>
Sorry, I completely missed this the first time.
Acked-by: Tim Deegan <tim@xen.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-02-06 16:35 [PATCH] x86/paging: use clear_guest() for zero-filling guest buffers Jan Beulich
2012-02-13 11:32 ` Ping: " Jan Beulich
2012-02-13 11:41 ` Tim Deegan
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