[Qemu-devel] [PATCH] numa: check for busy memory backend

[Qemu-devel] [PATCH] numa: check for busy memory backend

[Hu Tao]

..to prevent one memory backend from being used by more than one numa
node.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
---
 numa.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/numa.c b/numa.c
index e471afe..6c1c554 100644
--- a/numa.c
+++ b/numa.c
@@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
             exit(1);
         }
 
+        if (memory_region_is_mapped(seg)) {
+            char *path = object_get_canonical_path_component(OBJECT(backend));
+            error_report("memory backend %s is busy", path);
+            g_free(path);
+            exit(1);
+        }
+
         memory_region_add_subregion(mr, addr, seg);
         vmstate_register_ram_global(seg);
         addr += size;
-- 
1.9.3

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Igor Mammedov]

On Wed, 25 Jun 2014 17:04:14 +0800
Hu Tao <hutao@cn.fujitsu.com> wrote:

> ..to prevent one memory backend from being used by more than one numa
> node.
> 
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> ---
>  numa.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/numa.c b/numa.c
> index e471afe..6c1c554 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
>              exit(1);
>          }
>  
> +        if (memory_region_is_mapped(seg)) {
> +            char *path = object_get_canonical_path_component(OBJECT(backend));
> +            error_report("memory backend %s is busy", path);
> +            g_free(path);
> +            exit(1);
s/1/EXIT_FAILURE/ please

> +        }
> +
>          memory_region_add_subregion(mr, addr, seg);
>          vmstate_register_ram_global(seg);
>          addr += size;

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Markus Armbruster]

Igor Mammedov <imammedo@redhat.com> writes:

> On Wed, 25 Jun 2014 17:04:14 +0800
> Hu Tao <hutao@cn.fujitsu.com> wrote:
>
>> ..to prevent one memory backend from being used by more than one numa
>> node.
>> 
>> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
>> ---
>>  numa.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>> 
>> diff --git a/numa.c b/numa.c
>> index e471afe..6c1c554 100644
>> --- a/numa.c
>> +++ b/numa.c
>> @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
>>              exit(1);
>>          }
>>  
>> +        if (memory_region_is_mapped(seg)) {
>> +            char *path = object_get_canonical_path_component(OBJECT(backend));
>> +            error_report("memory backend %s is busy", path);
>> +            g_free(path);
>> +            exit(1);
> s/1/EXIT_FAILURE/ please

I count >600 instances of exit() with a numeric argument (not counting
some 50 sys.exit() in Python code), but less than 40 using EXIT_SUCCESS
or EXIT_FAILURE.

The abstraction provided by EXIT_SUCCESS / EXIT_FAILURE is basically
worthless anyway.

>
>> +        }
>> +
>>          memory_region_add_subregion(mr, addr, seg);
>>          vmstate_register_ram_global(seg);
>>          addr += size;

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Michael S. Tsirkin]

On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> ..to prevent one memory backend from being used by more than one numa
> node.

Thanks, but please always make the msg content self-contained
so it can be understood without the subject.
E.g. here, just drop "..to".

Are you sure we want this? Is there a chance sharing a backend
can be useful?

Igor, what's your take?

> 
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> ---
>  numa.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/numa.c b/numa.c
> index e471afe..6c1c554 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
>              exit(1);
>          }
>  
> +        if (memory_region_is_mapped(seg)) {
> +            char *path = object_get_canonical_path_component(OBJECT(backend));
> +            error_report("memory backend %s is busy", path);
> +            g_free(path);
> +            exit(1);
> +        }
> +
>          memory_region_add_subregion(mr, addr, seg);
>          vmstate_register_ram_global(seg);
>          addr += size;
> -- 
> 1.9.3

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Hu Tao]

On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > ..to prevent one memory backend from being used by more than one numa
> > node.
> 
> Thanks, but please always make the msg content self-contained
> so it can be understood without the subject.
> E.g. here, just drop "..to".
> 
> Are you sure we want this? Is there a chance sharing a backend
> can be useful?

This patch is actually a bug fix. Even if we will want backend sharing, we
can do it after.

> 
> Igor, what's your take?
> 
> > 
> > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > ---
> >  numa.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/numa.c b/numa.c
> > index e471afe..6c1c554 100644
> > --- a/numa.c
> > +++ b/numa.c
> > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> >              exit(1);
> >          }
> >  
> > +        if (memory_region_is_mapped(seg)) {
> > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > +            error_report("memory backend %s is busy", path);
> > +            g_free(path);
> > +            exit(1);
> > +        }
> > +
> >          memory_region_add_subregion(mr, addr, seg);
> >          vmstate_register_ram_global(seg);
> >          addr += size;
> > -- 
> > 1.9.3

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Michael S. Tsirkin]

On Mon, Jun 30, 2014 at 01:33:42PM +0800, Hu Tao wrote:
> On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> > On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > > ..to prevent one memory backend from being used by more than one numa
> > > node.
> > 
> > Thanks, but please always make the msg content self-contained
> > so it can be understood without the subject.
> > E.g. here, just drop "..to".
> > 
> > Are you sure we want this? Is there a chance sharing a backend
> > can be useful?
> 
> This patch is actually a bug fix.

It is?  What is the bug and how to reproduce it?
I am not sure we should write a ton of code to validate qemu
configuration, as long as qemu does not assert.

> Even if we will want backend sharing, we
> can do it after.

By reverting this patch? So why merge it?

> > 
> > Igor, what's your take?
> > 
> > > 
> > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > ---
> > >  numa.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/numa.c b/numa.c
> > > index e471afe..6c1c554 100644
> > > --- a/numa.c
> > > +++ b/numa.c
> > > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> > >              exit(1);
> > >          }
> > >  
> > > +        if (memory_region_is_mapped(seg)) {
> > > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > > +            error_report("memory backend %s is busy", path);
> > > +            g_free(path);
> > > +            exit(1);
> > > +        }
> > > +
> > >          memory_region_add_subregion(mr, addr, seg);
> > >          vmstate_register_ram_global(seg);
> > >          addr += size;
> > > -- 
> > > 1.9.3

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Hu Tao]

On Mon, Jun 30, 2014 at 09:53:20AM +0300, Michael S. Tsirkin wrote:
> On Mon, Jun 30, 2014 at 01:33:42PM +0800, Hu Tao wrote:
> > On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> > > On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > > > ..to prevent one memory backend from being used by more than one numa
> > > > node.
> > > 
> > > Thanks, but please always make the msg content self-contained
> > > so it can be understood without the subject.
> > > E.g. here, just drop "..to".
> > > 
> > > Are you sure we want this? Is there a chance sharing a backend
> > > can be useful?
> > 
> > This patch is actually a bug fix.
> 
> It is?  What is the bug and how to reproduce it?

If user specifies the same memory backend for two numa nodes:

./x86_64-softmmu/qemu-system-x86_64 -hda /home/data/libvirt-images/f18.img  -m 512M \
-qmp unix:/tmp/m,server,nowait -monitor stdio -enable-kvm \
-object memory-backend-ram,size=256M,id=ram0 \
-numa node,nodeid=0,memdev=ram0 \
-numa node,nodeid=1,memdev=ram0

> I am not sure we should write a ton of code to validate qemu
> configuration, as long as qemu does not assert.

It seems qemu does not provide a way to disable assert currently.
Even if I removed asserts on the code path in my test, there is another
problem that it hits an infinite in render_memory_region().

> 
> > Even if we will want backend sharing, we
> > can do it after.
> 
> By reverting this patch? So why merge it?

The point is qemu doesn't fire a bug no matter what user inputs.

> 
> > > 
> > > Igor, what's your take?
> > > 
> > > > 
> > > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > > ---
> > > >  numa.c | 7 +++++++
> > > >  1 file changed, 7 insertions(+)
> > > > 
> > > > diff --git a/numa.c b/numa.c
> > > > index e471afe..6c1c554 100644
> > > > --- a/numa.c
> > > > +++ b/numa.c
> > > > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> > > >              exit(1);
> > > >          }
> > > >  
> > > > +        if (memory_region_is_mapped(seg)) {
> > > > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > > > +            error_report("memory backend %s is busy", path);
> > > > +            g_free(path);
> > > > +            exit(1);
> > > > +        }
> > > > +
> > > >          memory_region_add_subregion(mr, addr, seg);
> > > >          vmstate_register_ram_global(seg);
> > > >          addr += size;
> > > > -- 
> > > > 1.9.3

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Michael S. Tsirkin]

On Mon, Jun 30, 2014 at 03:46:56PM +0800, Hu Tao wrote:
> On Mon, Jun 30, 2014 at 09:53:20AM +0300, Michael S. Tsirkin wrote:
> > On Mon, Jun 30, 2014 at 01:33:42PM +0800, Hu Tao wrote:
> > > On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> > > > On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > > > > ..to prevent one memory backend from being used by more than one numa
> > > > > node.
> > > > 
> > > > Thanks, but please always make the msg content self-contained
> > > > so it can be understood without the subject.
> > > > E.g. here, just drop "..to".
> > > > 
> > > > Are you sure we want this? Is there a chance sharing a backend
> > > > can be useful?
> > > 
> > > This patch is actually a bug fix.
> > 
> > It is?  What is the bug and how to reproduce it?
> 
> If user specifies the same memory backend for two numa nodes:
> 
> ./x86_64-softmmu/qemu-system-x86_64 -hda /home/data/libvirt-images/f18.img  -m 512M \
> -qmp unix:/tmp/m,server,nowait -monitor stdio -enable-kvm \
> -object memory-backend-ram,size=256M,id=ram0 \
> -numa node,nodeid=0,memdev=ram0 \
> -numa node,nodeid=1,memdev=ram0
> 
> > I am not sure we should write a ton of code to validate qemu
> > configuration, as long as qemu does not assert.
> 
> It seems qemu does not provide a way to disable assert currently.
> Even if I removed asserts on the code path in my test, there is another
> problem that it hits an infinite in render_memory_region().

OK so this is what commit log should say:
--->
Specifying the same memory region twice leads to an assert:

./x86_64-softmmu/qemu-system-x86_64 -m 512M -enable-kvm -object
memory-backend-ram,size=256M,id=ram0 -numa node,nodeid=0,memdev=ram0
-numa node,nodeid=1,memdev=ram0
qemu-system-x86_64: /scm/qemu/memory.c:1506:
memory_region_add_subregion_common: Assertion `!subregion->container'
failed.
Aborted (core dumped)

Detect and exit with an error message instead.
<---

See? Explain why your patch makes sense, don't just repeat what it does.

> > 
> > > Even if we will want backend sharing, we
> > > can do it after.
> > 
> > By reverting this patch? So why merge it?
> 
> The point is qemu doesn't fire a bug no matter what user inputs.
> 
> > 
> > > > 
> > > > Igor, what's your take?
> > > > 
> > > > > 
> > > > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > > > ---
> > > > >  numa.c | 7 +++++++
> > > > >  1 file changed, 7 insertions(+)
> > > > > 
> > > > > diff --git a/numa.c b/numa.c
> > > > > index e471afe..6c1c554 100644
> > > > > --- a/numa.c
> > > > > +++ b/numa.c
> > > > > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> > > > >              exit(1);
> > > > >          }
> > > > >  
> > > > > +        if (memory_region_is_mapped(seg)) {
> > > > > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > > > > +            error_report("memory backend %s is busy", path);

That's not very clear. How about:
	memory backend %s is used multiple times. Each -numa option must use a different memdev value.

> > > > > +            g_free(path);

As we are going to exit anyway, it does not make sense to bother with this.

> > > > > +            exit(1);
> > > > > +        }
> > > > > +
> > > > >          memory_region_add_subregion(mr, addr, seg);
> > > > >          vmstate_register_ram_global(seg);
> > > > >          addr += size;
> > > > > -- 
> > > > > 1.9.3

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Igor Mammedov]

On Mon, 30 Jun 2014 11:28:07 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Jun 30, 2014 at 03:46:56PM +0800, Hu Tao wrote:
> > On Mon, Jun 30, 2014 at 09:53:20AM +0300, Michael S. Tsirkin wrote:
> > > On Mon, Jun 30, 2014 at 01:33:42PM +0800, Hu Tao wrote:
> > > > On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> > > > > On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > > > > > ..to prevent one memory backend from being used by more than one numa
> > > > > > node.
> > > > > 
> > > > > Thanks, but please always make the msg content self-contained
> > > > > so it can be understood without the subject.
> > > > > E.g. here, just drop "..to".
> > > > > 
> > > > > Are you sure we want this? Is there a chance sharing a backend
> > > > > can be useful?
> > > > 
> > > > This patch is actually a bug fix.
> > > 
> > > It is?  What is the bug and how to reproduce it?
> > 
> > If user specifies the same memory backend for two numa nodes:
> > 
> > ./x86_64-softmmu/qemu-system-x86_64 -hda /home/data/libvirt-images/f18.img  -m 512M \
> > -qmp unix:/tmp/m,server,nowait -monitor stdio -enable-kvm \
> > -object memory-backend-ram,size=256M,id=ram0 \
> > -numa node,nodeid=0,memdev=ram0 \
> > -numa node,nodeid=1,memdev=ram0
> > 
> > > I am not sure we should write a ton of code to validate qemu
> > > configuration, as long as qemu does not assert.
> > 
> > It seems qemu does not provide a way to disable assert currently.
> > Even if I removed asserts on the code path in my test, there is another
> > problem that it hits an infinite in render_memory_region().
> 
> OK so this is what commit log should say:
> --->
> Specifying the same memory region twice leads to an assert:
> 
> ./x86_64-softmmu/qemu-system-x86_64 -m 512M -enable-kvm -object
> memory-backend-ram,size=256M,id=ram0 -numa node,nodeid=0,memdev=ram0
> -numa node,nodeid=1,memdev=ram0
> qemu-system-x86_64: /scm/qemu/memory.c:1506:
> memory_region_add_subregion_common: Assertion `!subregion->container'
> failed.
> Aborted (core dumped)
> 
> Detect and exit with an error message instead.
> <---
with  fixed-up commit message:
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> 
> See? Explain why your patch makes sense, don't just repeat what it does.
> 
> > > 
> > > > Even if we will want backend sharing, we
> > > > can do it after.
> > > 
> > > By reverting this patch? So why merge it?
> > 
> > The point is qemu doesn't fire a bug no matter what user inputs.
> > 
> > > 
> > > > > 
> > > > > Igor, what's your take?
> > > > > 
> > > > > > 
> > > > > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > > > > ---
> > > > > >  numa.c | 7 +++++++
> > > > > >  1 file changed, 7 insertions(+)
> > > > > > 
> > > > > > diff --git a/numa.c b/numa.c
> > > > > > index e471afe..6c1c554 100644
> > > > > > --- a/numa.c
> > > > > > +++ b/numa.c
> > > > > > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> > > > > >              exit(1);
> > > > > >          }
> > > > > >  
> > > > > > +        if (memory_region_is_mapped(seg)) {
> > > > > > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > > > > > +            error_report("memory backend %s is busy", path);
> 
> That's not very clear. How about:
> 	memory backend %s is used multiple times. Each -numa option must use a different memdev value.
> 
> > > > > > +            g_free(path);
> 
> As we are going to exit anyway, it does not make sense to bother with this.
> 
> > > > > > +            exit(1);
> > > > > > +        }
> > > > > > +
> > > > > >          memory_region_add_subregion(mr, addr, seg);
> > > > > >          vmstate_register_ram_global(seg);
> > > > > >          addr += size;
> > > > > > -- 
> > > > > > 1.9.3
> 

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Michael S. Tsirkin]

On Mon, Jun 30, 2014 at 10:48:22AM +0200, Igor Mammedov wrote:
> On Mon, 30 Jun 2014 11:28:07 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Mon, Jun 30, 2014 at 03:46:56PM +0800, Hu Tao wrote:
> > > On Mon, Jun 30, 2014 at 09:53:20AM +0300, Michael S. Tsirkin wrote:
> > > > On Mon, Jun 30, 2014 at 01:33:42PM +0800, Hu Tao wrote:
> > > > > On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> > > > > > On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > > > > > > ..to prevent one memory backend from being used by more than one numa
> > > > > > > node.
> > > > > > 
> > > > > > Thanks, but please always make the msg content self-contained
> > > > > > so it can be understood without the subject.
> > > > > > E.g. here, just drop "..to".
> > > > > > 
> > > > > > Are you sure we want this? Is there a chance sharing a backend
> > > > > > can be useful?
> > > > > 
> > > > > This patch is actually a bug fix.
> > > > 
> > > > It is?  What is the bug and how to reproduce it?
> > > 
> > > If user specifies the same memory backend for two numa nodes:
> > > 
> > > ./x86_64-softmmu/qemu-system-x86_64 -hda /home/data/libvirt-images/f18.img  -m 512M \
> > > -qmp unix:/tmp/m,server,nowait -monitor stdio -enable-kvm \
> > > -object memory-backend-ram,size=256M,id=ram0 \
> > > -numa node,nodeid=0,memdev=ram0 \
> > > -numa node,nodeid=1,memdev=ram0
> > > 
> > > > I am not sure we should write a ton of code to validate qemu
> > > > configuration, as long as qemu does not assert.
> > > 
> > > It seems qemu does not provide a way to disable assert currently.
> > > Even if I removed asserts on the code path in my test, there is another
> > > problem that it hits an infinite in render_memory_region().
> > 
> > OK so this is what commit log should say:
> > --->
> > Specifying the same memory region twice leads to an assert:
> > 
> > ./x86_64-softmmu/qemu-system-x86_64 -m 512M -enable-kvm -object
> > memory-backend-ram,size=256M,id=ram0 -numa node,nodeid=0,memdev=ram0
> > -numa node,nodeid=1,memdev=ram0
> > qemu-system-x86_64: /scm/qemu/memory.c:1506:
> > memory_region_add_subregion_common: Assertion `!subregion->container'
> > failed.
> > Aborted (core dumped)
> > 
> > Detect and exit with an error message instead.
> > <---
> with  fixed-up commit message:
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>

Sorry I want the error message fixed up too.

> > 
> > See? Explain why your patch makes sense, don't just repeat what it does.
> > 
> > > > 
> > > > > Even if we will want backend sharing, we
> > > > > can do it after.
> > > > 
> > > > By reverting this patch? So why merge it?
> > > 
> > > The point is qemu doesn't fire a bug no matter what user inputs.
> > > 
> > > > 
> > > > > > 
> > > > > > Igor, what's your take?
> > > > > > 
> > > > > > > 
> > > > > > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > > > > > ---
> > > > > > >  numa.c | 7 +++++++
> > > > > > >  1 file changed, 7 insertions(+)
> > > > > > > 
> > > > > > > diff --git a/numa.c b/numa.c
> > > > > > > index e471afe..6c1c554 100644
> > > > > > > --- a/numa.c
> > > > > > > +++ b/numa.c
> > > > > > > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> > > > > > >              exit(1);
> > > > > > >          }
> > > > > > >  
> > > > > > > +        if (memory_region_is_mapped(seg)) {
> > > > > > > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > > > > > > +            error_report("memory backend %s is busy", path);
> > 
> > That's not very clear. How about:
> > 	memory backend %s is used multiple times. Each -numa option must use a different memdev value.
> > 
> > > > > > > +            g_free(path);
> > 
> > As we are going to exit anyway, it does not make sense to bother with this.
> > 
> > > > > > > +            exit(1);
> > > > > > > +        }
> > > > > > > +
> > > > > > >          memory_region_add_subregion(mr, addr, seg);
> > > > > > >          vmstate_register_ram_global(seg);
> > > > > > >          addr += size;
> > > > > > > -- 
> > > > > > > 1.9.3
> > 

Re: [Qemu-devel] [PATCH] numa: check for busy memory backend

[Hu Tao]

On Mon, Jun 30, 2014 at 12:12:20PM +0300, Michael S. Tsirkin wrote:
> On Mon, Jun 30, 2014 at 10:48:22AM +0200, Igor Mammedov wrote:
> > On Mon, 30 Jun 2014 11:28:07 +0300
> > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > 
> > > On Mon, Jun 30, 2014 at 03:46:56PM +0800, Hu Tao wrote:
> > > > On Mon, Jun 30, 2014 at 09:53:20AM +0300, Michael S. Tsirkin wrote:
> > > > > On Mon, Jun 30, 2014 at 01:33:42PM +0800, Hu Tao wrote:
> > > > > > On Sun, Jun 29, 2014 at 06:20:22PM +0300, Michael S. Tsirkin wrote:
> > > > > > > On Wed, Jun 25, 2014 at 05:04:14PM +0800, Hu Tao wrote:
> > > > > > > > ..to prevent one memory backend from being used by more than one numa
> > > > > > > > node.
> > > > > > > 
> > > > > > > Thanks, but please always make the msg content self-contained
> > > > > > > so it can be understood without the subject.
> > > > > > > E.g. here, just drop "..to".
> > > > > > > 
> > > > > > > Are you sure we want this? Is there a chance sharing a backend
> > > > > > > can be useful?
> > > > > > 
> > > > > > This patch is actually a bug fix.
> > > > > 
> > > > > It is?  What is the bug and how to reproduce it?
> > > > 
> > > > If user specifies the same memory backend for two numa nodes:
> > > > 
> > > > ./x86_64-softmmu/qemu-system-x86_64 -hda /home/data/libvirt-images/f18.img  -m 512M \
> > > > -qmp unix:/tmp/m,server,nowait -monitor stdio -enable-kvm \
> > > > -object memory-backend-ram,size=256M,id=ram0 \
> > > > -numa node,nodeid=0,memdev=ram0 \
> > > > -numa node,nodeid=1,memdev=ram0
> > > > 
> > > > > I am not sure we should write a ton of code to validate qemu
> > > > > configuration, as long as qemu does not assert.
> > > > 
> > > > It seems qemu does not provide a way to disable assert currently.
> > > > Even if I removed asserts on the code path in my test, there is another
> > > > problem that it hits an infinite in render_memory_region().
> > > 
> > > OK so this is what commit log should say:
> > > --->
> > > Specifying the same memory region twice leads to an assert:
> > > 
> > > ./x86_64-softmmu/qemu-system-x86_64 -m 512M -enable-kvm -object
> > > memory-backend-ram,size=256M,id=ram0 -numa node,nodeid=0,memdev=ram0
> > > -numa node,nodeid=1,memdev=ram0
> > > qemu-system-x86_64: /scm/qemu/memory.c:1506:
> > > memory_region_add_subregion_common: Assertion `!subregion->container'
> > > failed.
> > > Aborted (core dumped)
> > > 
> > > Detect and exit with an error message instead.
> > > <---
> > with  fixed-up commit message:
> > Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> 
> Sorry I want the error message fixed up too.

Yes your error message is more clear. I'll send v2. Thanks for review.

Regards,
Hu

> 
> > > 
> > > See? Explain why your patch makes sense, don't just repeat what it does.
> > > 
> > > > > 
> > > > > > Even if we will want backend sharing, we
> > > > > > can do it after.
> > > > > 
> > > > > By reverting this patch? So why merge it?
> > > > 
> > > > The point is qemu doesn't fire a bug no matter what user inputs.
> > > > 
> > > > > 
> > > > > > > 
> > > > > > > Igor, what's your take?
> > > > > > > 
> > > > > > > > 
> > > > > > > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > > > > > > ---
> > > > > > > >  numa.c | 7 +++++++
> > > > > > > >  1 file changed, 7 insertions(+)
> > > > > > > > 
> > > > > > > > diff --git a/numa.c b/numa.c
> > > > > > > > index e471afe..6c1c554 100644
> > > > > > > > --- a/numa.c
> > > > > > > > +++ b/numa.c
> > > > > > > > @@ -279,6 +279,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
> > > > > > > >              exit(1);
> > > > > > > >          }
> > > > > > > >  
> > > > > > > > +        if (memory_region_is_mapped(seg)) {
> > > > > > > > +            char *path = object_get_canonical_path_component(OBJECT(backend));
> > > > > > > > +            error_report("memory backend %s is busy", path);
> > > 
> > > That's not very clear. How about:
> > > 	memory backend %s is used multiple times. Each -numa option must use a different memdev value.
> > > 
> > > > > > > > +            g_free(path);
> > > 
> > > As we are going to exit anyway, it does not make sense to bother with this.
> > > 
> > > > > > > > +            exit(1);
> > > > > > > > +        }
> > > > > > > > +
> > > > > > > >          memory_region_add_subregion(mr, addr, seg);
> > > > > > > >          vmstate_register_ram_global(seg);
> > > > > > > >          addr += size;
> > > > > > > > -- 
> > > > > > > > 1.9.3
> > >