Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On 14.06.2011, at 17:24, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 14.06.2011, at 13:48, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue?
The fact that you can only map a single region? Then do a counter and fail
when it's 1.
That is what we were doing before: succeeding the first time and
failing from the second time on.
By coincidence the second time was the range 0xa-0xb so
everything worked as expected, but it wasn't obvious why.
I am just trying to make sure that one year from now it will be clear
just looking at the code why it works.
If you don't want to map the VGA region as memory slot, why not change the
actual mapping code in the cirrus adapter?
Because I didn't want to introduce any ugly if (xen_enable()) in generic
code, if it is that simple to catch the issue from xen specific code.
Well sure, but 2 years from now yet another region will be introduced that
might even be registered before the FB and everyone's puzzled again :). How
about you print a warning when anyone tries to map anything after the first
map? Or - as Jan suggests - implement multiple regions.
If you prefer, you could even check for the VGA range as known broken and
only print warnings on others.
I can do that (actually we already do it) but it wouldn't change the
fact that if somebody modifies hw/cirrus_vga.c:map_linear_vram to call
cpu_register_physical_memory_log for the legacy range first, it would
break xen, that is the problem I was trying to solve.
In order to make the code more reliable, and also catch the scenario
where another region is registered before the framebuffer, we could do
something like this, but it is not very pretty:
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..de1e724 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -214,6 +214,7 @@ static int xen_add_to_physmap(XenIOState *state,
unsigned long i = 0;
int rc = 0;
XenPhysmap *physmap = NULL;
+RAMBlock *block;
if (get_physmapping(state, start_addr, size)) {
return 0;
@@ -221,7 +222,16 @@ static int xen_add_to_physmap(XenIOState *state,
if (size = 0) {
return -1;
}
+/* only add the vga vram to physmap */
Please add a comment here, explaining that Xen can only handle a single dirty
log region for now, and that we want the linear framebuffer to be that region.
Also, please resend with proper patch headers and I'll pull it into the
xen-next tree.
Alex
+QLIST_FOREACH(block, ram_list.blocks, next) {
+if (!strcmp(block-idstr, vga.vram) block-offset == phys_offset
+ start_addr 0xb) {
+goto go_physmap;
+}
+}
+return -1;
+go_physmap:
DPRINTF(mapping vram to %llx - %llx, from %llx\n, start_addr,
start_addr + size, phys_offset);
for (i = 0; i size TARGET_PAGE_BITS; i++) {
unsigned long idx = (phys_offset TARGET_PAGE_BITS) + i;
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On Wed, 15 Jun 2011, Alexander Graf wrote: Please add a comment here, explaining that Xen can only handle a single dirty log region for now, and that we want the linear framebuffer to be that region. Also, please resend with proper patch headers and I'll pull it into the xen-next tree. OK, I'll do that.
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On 2011-06-14 12:54, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue? The
fact that you can only map a single region? Then do a counter and fail when
it's 1. If you don't want to map the VGA region as memory slot, why not
change the actual mapping code in the cirrus adapter?
Err, please no if (xen_enabled()) in that code. We just got rid of the
kvm_enabled() mess. And it doesn't scale, it would be required in e1000
as well e.g.
BTW, if Xen is not able to track more than one dirty region, I think
it's time to fix that limitation. At some point it may no longer be
possible to work around it (who knows how the new memory API will look
like in this regard).
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On Tue, 14 Jun 2011, Jan Kiszka wrote:
On 2011-06-14 12:54, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue? The
fact that you can only map a single region? Then do a counter and fail when
it's 1. If you don't want to map the VGA region as memory slot, why not
change the actual mapping code in the cirrus adapter?
Err, please no if (xen_enabled()) in that code. We just got rid of the
kvm_enabled() mess. And it doesn't scale, it would be required in e1000
as well e.g.
agreed
BTW, if Xen is not able to track more than one dirty region, I think
it's time to fix that limitation. At some point it may no longer be
possible to work around it (who knows how the new memory API will look
like in this regard).
you are right, however it is not a simple fix and at present we don't
actually need to track more than one region...
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue? The
fact that you can only map a single region? Then do a counter and fail when
it's 1.
That is what we were doing before: succeeding the first time and
failing from the second time on.
By coincidence the second time was the range 0xa-0xb so
everything worked as expected, but it wasn't obvious why.
I am just trying to make sure that one year from now it will be clear
just looking at the code why it works.
If you don't want to map the VGA region as memory slot, why not change the
actual mapping code in the cirrus adapter?
Because I didn't want to introduce any ugly if (xen_enable()) in generic
code, if it is that simple to catch the issue from xen specific code.
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On 14.06.2011, at 13:48, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue? The
fact that you can only map a single region? Then do a counter and fail when
it's 1.
That is what we were doing before: succeeding the first time and
failing from the second time on.
By coincidence the second time was the range 0xa-0xb so
everything worked as expected, but it wasn't obvious why.
I am just trying to make sure that one year from now it will be clear
just looking at the code why it works.
If you don't want to map the VGA region as memory slot, why not change the
actual mapping code in the cirrus adapter?
Because I didn't want to introduce any ugly if (xen_enable()) in generic
code, if it is that simple to catch the issue from xen specific code.
Well sure, but 2 years from now yet another region will be introduced that
might even be registered before the FB and everyone's puzzled again :). How
about you print a warning when anyone tries to map anything after the first
map? Or - as Jan suggests - implement multiple regions.
If you prefer, you could even check for the VGA range as known broken and
only print warnings on others.
Alex
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On 2011-06-14 13:50, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Jan Kiszka wrote:
On 2011-06-14 12:54, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue? The
fact that you can only map a single region? Then do a counter and fail when
it's 1. If you don't want to map the VGA region as memory slot, why not
change the actual mapping code in the cirrus adapter?
Err, please no if (xen_enabled()) in that code. We just got rid of the
kvm_enabled() mess. And it doesn't scale, it would be required in e1000
as well e.g.
agreed
[Actually, e1000 is not using dirty logging but coalesced MMIO.]
BTW, if Xen is not able to track more than one dirty region, I think
it's time to fix that limitation. At some point it may no longer be
possible to work around it (who knows how the new memory API will look
like in this regard).
you are right, however it is not a simple fix and at present we don't
actually need to track more than one region...
Well, you already miss dirty logged VGA/VBE memory access this way
(everything that goes to legacy VGA mem, not the framebuffer BAR). Grub
provides a really poor use experience in that mode.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 14.06.2011, at 13:48, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 03.06.2011, at 17:56, stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellini stefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellini stefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr = 0xa start_addr + size = 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue?
The fact that you can only map a single region? Then do a counter and fail
when it's 1.
That is what we were doing before: succeeding the first time and
failing from the second time on.
By coincidence the second time was the range 0xa-0xb so
everything worked as expected, but it wasn't obvious why.
I am just trying to make sure that one year from now it will be clear
just looking at the code why it works.
If you don't want to map the VGA region as memory slot, why not change the
actual mapping code in the cirrus adapter?
Because I didn't want to introduce any ugly if (xen_enable()) in generic
code, if it is that simple to catch the issue from xen specific code.
Well sure, but 2 years from now yet another region will be introduced that
might even be registered before the FB and everyone's puzzled again :). How
about you print a warning when anyone tries to map anything after the first
map? Or - as Jan suggests - implement multiple regions.
If you prefer, you could even check for the VGA range as known broken and
only print warnings on others.
I can do that (actually we already do it) but it wouldn't change the
fact that if somebody modifies hw/cirrus_vga.c:map_linear_vram to call
cpu_register_physical_memory_log for the legacy range first, it would
break xen, that is the problem I was trying to solve.
In order to make the code more reliable, and also catch the scenario
where another region is registered before the framebuffer, we could do
something like this, but it is not very pretty:
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..de1e724 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -214,6 +214,7 @@ static int xen_add_to_physmap(XenIOState *state,
unsigned long i = 0;
int rc = 0;
XenPhysmap *physmap = NULL;
+RAMBlock *block;
if (get_physmapping(state, start_addr, size)) {
return 0;
@@ -221,7 +222,16 @@ static int xen_add_to_physmap(XenIOState *state,
if (size = 0) {
return -1;
}
+/* only add the vga vram to physmap */
+QLIST_FOREACH(block, ram_list.blocks, next) {
+if (!strcmp(block-idstr, vga.vram) block-offset == phys_offset
+ start_addr 0xb) {
+goto go_physmap;
+}
+}
+return -1;
+go_physmap:
DPRINTF(mapping vram to %llx - %llx, from %llx\n, start_addr, start_addr
+ size, phys_offset);
for (i = 0; i size TARGET_PAGE_BITS; i++) {
unsigned long idx = (phys_offset TARGET_PAGE_BITS) + i;
Re: [Qemu-devel] [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On 06/14/2011 05:24 PM, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 14.06.2011, at 13:48, Stefano Stabellini wrote:
On Tue, 14 Jun 2011, Alexander Graf wrote:
On 03.06.2011, at 17:56,stefano.stabell...@eu.citrix.com
stefano.stabell...@eu.citrix.com wrote:
From: Stefano Stabellinistefano.stabell...@eu.citrix.com
Xen can only do dirty bit tracking for one memory region, so we should
explicitly avoid trying to track the legacy VGA region between 0xa
and 0xb, rather than trying and failing.
Signed-off-by: Stefano Stabellinistefano.stabell...@eu.citrix.com
---
xen-all.c |4
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..1fdc2e8 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state,
if (get_physmapping(state, start_addr, size)) {
return 0;
}
+/* do not try to map legacy VGA memory */
+if (start_addr= 0xa start_addr + size= 0xb) {
I don't quite like the hardcoded range here. What exactly is the issue? The fact
that you can only map a single region? Then do a counter and fail when it's 1.
That is what we were doing before: succeeding the first time and
failing from the second time on.
By coincidence the second time was the range 0xa-0xb so
everything worked as expected, but it wasn't obvious why.
I am just trying to make sure that one year from now it will be clear
just looking at the code why it works.
If you don't want to map the VGA region as memory slot, why not change the
actual mapping code in the cirrus adapter?
Because I didn't want to introduce any ugly if (xen_enable()) in generic
code, if it is that simple to catch the issue from xen specific code.
Well sure, but 2 years from now yet another region will be introduced that
might even be registered before the FB and everyone's puzzled again :). How
about you print a warning when anyone tries to map anything after the first
map? Or - as Jan suggests - implement multiple regions.
If you prefer, you could even check for the VGA range as known broken and
only print warnings on others.
I can do that (actually we already do it) but it wouldn't change the
fact that if somebody modifies hw/cirrus_vga.c:map_linear_vram to call
cpu_register_physical_memory_log for the legacy range first, it would
break xen, that is the problem I was trying to solve.
In order to make the code more reliable, and also catch the scenario
where another region is registered before the framebuffer, we could do
something like this, but it is not very pretty:
I agree, but it's probably the most pretty one I've seen so far. I'll
let others comment on it too before taking it in.
Alex
diff --git a/xen-all.c b/xen-all.c
index 9a5c3ec..de1e724 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -214,6 +214,7 @@ static int xen_add_to_physmap(XenIOState *state,
unsigned long i = 0;
int rc = 0;
XenPhysmap *physmap = NULL;
+RAMBlock *block;
if (get_physmapping(state, start_addr, size)) {
return 0;
@@ -221,7 +222,16 @@ static int xen_add_to_physmap(XenIOState *state,
if (size= 0) {
return -1;
}
+/* only add the vga vram to physmap */
+QLIST_FOREACH(block,ram_list.blocks, next) {
+if (!strcmp(block-idstr, vga.vram) block-offset == phys_offset
+ start_addr 0xb) {
+goto go_physmap;
+}
+}
+return -1;
+go_physmap:
DPRINTF(mapping vram to %llx - %llx, from %llx\n, start_addr,
start_addr + size, phys_offset);
for (i = 0; i size TARGET_PAGE_BITS; i++) {
unsigned long idx = (phys_offset TARGET_PAGE_BITS) + i;
