dma/i82374: avoid double creation of i82374 device
diff mbox

Message ID 20170901110332.32650-1-otubo@redhat.com
State New
Headers show

Commit Message

Eduardo Otubo Sept. 1, 2017, 11:03 a.m. UTC
When used with the following command line:

 ./ppc64-softmmu/qemu-system-ppc64 -S -machine 40p,accel=tcg -device i82374

QEMU with machine type 40p already creates the device i82374. If
specified in the command line, it will try to create it again, hence
generating the error. One way to avoid this problem is to set
user_creatable=false.

Signed-off-by: Eduardo Otubo <otubo@redhat.com>
---
 hw/dma/i82374.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Eduardo Habkost Sept. 1, 2017, 2:30 p.m. UTC | #1
i82374 is compiled in only on ppc and sh4, so I'm CCing the
maintainers for those architectures.

On Fri, Sep 01, 2017 at 01:03:32PM +0200, Eduardo Otubo wrote:
> When used with the following command line:
> 
>  ./ppc64-softmmu/qemu-system-ppc64 -S -machine 40p,accel=tcg -device i82374
> 
> QEMU with machine type 40p already creates the device i82374. If
> specified in the command line, it will try to create it again, hence
> generating the error.

Which error?


>                       One way to avoid this problem is to set
> user_creatable=false.
> 
> Signed-off-by: Eduardo Otubo <otubo@redhat.com>

The patch does more than just avoiding double creation: it
prevents usage of "-device i82374" completely.

Maybe nobody needs it to work with -device today (would the
device even work?) and it is OK to set user_creatable=false until
we fix the crash.  But we need to be sure of that.

> ---
>  hw/dma/i82374.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/dma/i82374.c b/hw/dma/i82374.c
> index 6c0f975df0..5275d822e0 100644
> --- a/hw/dma/i82374.c
> +++ b/hw/dma/i82374.c
> @@ -139,6 +139,7 @@ static void i82374_class_init(ObjectClass *klass, void *data)
>      dc->realize = i82374_realize;
>      dc->vmsd = &vmstate_i82374;
>      dc->props = i82374_properties;
> +    dc->user_creatable = false;

A "Reason:" comment explaining why user_creatable=false is
mandatory.  See the comment above user_creatable declaration in
qdev-core.h for reference.

I suggest the following:

    /*
     * Reason: i82374_realize() crashes (assertion failure inside isa_bus_dma()
     *         if the device is instantiated twice.
     */
Markus Armbruster Sept. 1, 2017, 3:34 p.m. UTC | #2
Eduardo Habkost <ehabkost@redhat.com> writes:

> i82374 is compiled in only on ppc and sh4, so I'm CCing the
> maintainers for those architectures.
>
> On Fri, Sep 01, 2017 at 01:03:32PM +0200, Eduardo Otubo wrote:
>> When used with the following command line:
>> 
>>  ./ppc64-softmmu/qemu-system-ppc64 -S -machine 40p,accel=tcg -device i82374
>> 
>> QEMU with machine type 40p already creates the device i82374. If
>> specified in the command line, it will try to create it again, hence
>> generating the error.
>
> Which error?
>
>
>>                       One way to avoid this problem is to set
>> user_creatable=false.
>> 
>> Signed-off-by: Eduardo Otubo <otubo@redhat.com>
>
> The patch does more than just avoiding double creation: it
> prevents usage of "-device i82374" completely.
>
> Maybe nobody needs it to work with -device today (would the
> device even work?) and it is OK to set user_creatable=false until
> we fix the crash.  But we need to be sure of that.
>
>> ---
>>  hw/dma/i82374.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/hw/dma/i82374.c b/hw/dma/i82374.c
>> index 6c0f975df0..5275d822e0 100644
>> --- a/hw/dma/i82374.c
>> +++ b/hw/dma/i82374.c
>> @@ -139,6 +139,7 @@ static void i82374_class_init(ObjectClass *klass, void *data)
>>      dc->realize = i82374_realize;
>>      dc->vmsd = &vmstate_i82374;
>>      dc->props = i82374_properties;
>> +    dc->user_creatable = false;
>
> A "Reason:" comment explaining why user_creatable=false is
> mandatory.  See the comment above user_creatable declaration in
> qdev-core.h for reference.
>
> I suggest the following:
>
>     /*
>      * Reason: i82374_realize() crashes (assertion failure inside isa_bus_dma()
>      *         if the device is instantiated twice.
>      */

We need to find out *why* it crashes.  Once we know, we can likely write
a better comment.
Eduardo Habkost Sept. 1, 2017, 3:44 p.m. UTC | #3
On Fri, Sep 01, 2017 at 05:34:34PM +0200, Markus Armbruster wrote:
> Eduardo Habkost <ehabkost@redhat.com> writes:
> 
> > i82374 is compiled in only on ppc and sh4, so I'm CCing the
> > maintainers for those architectures.
> >
> > On Fri, Sep 01, 2017 at 01:03:32PM +0200, Eduardo Otubo wrote:
> >> When used with the following command line:
> >> 
> >>  ./ppc64-softmmu/qemu-system-ppc64 -S -machine 40p,accel=tcg -device i82374
> >> 
> >> QEMU with machine type 40p already creates the device i82374. If
> >> specified in the command line, it will try to create it again, hence
> >> generating the error.
> >
> > Which error?
> >
> >
> >>                       One way to avoid this problem is to set
> >> user_creatable=false.
> >> 
> >> Signed-off-by: Eduardo Otubo <otubo@redhat.com>
> >
> > The patch does more than just avoiding double creation: it
> > prevents usage of "-device i82374" completely.
> >
> > Maybe nobody needs it to work with -device today (would the
> > device even work?) and it is OK to set user_creatable=false until
> > we fix the crash.  But we need to be sure of that.
> >
> >> ---
> >>  hw/dma/i82374.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >> 
> >> diff --git a/hw/dma/i82374.c b/hw/dma/i82374.c
> >> index 6c0f975df0..5275d822e0 100644
> >> --- a/hw/dma/i82374.c
> >> +++ b/hw/dma/i82374.c
> >> @@ -139,6 +139,7 @@ static void i82374_class_init(ObjectClass *klass, void *data)
> >>      dc->realize = i82374_realize;
> >>      dc->vmsd = &vmstate_i82374;
> >>      dc->props = i82374_properties;
> >> +    dc->user_creatable = false;
> >
> > A "Reason:" comment explaining why user_creatable=false is
> > mandatory.  See the comment above user_creatable declaration in
> > qdev-core.h for reference.
> >
> > I suggest the following:
> >
> >     /*
> >      * Reason: i82374_realize() crashes (assertion failure inside isa_bus_dma()
> >      *         if the device is instantiated twice.
> >      */
> 
> We need to find out *why* it crashes.  Once we know, we can likely write
> a better comment.

It crashes because isa_bus_dma() isn't supposed to be called
twice for the same bus.

Making isa_bus_dma()/DMA_init()/i82374_realize() return an error
instead of asserting would be even better than setting
user_creatable=false.
Aurelien Jarno Sept. 2, 2017, 9:15 a.m. UTC | #4
On 2017-09-01 11:30, Eduardo Habkost wrote:
> i82374 is compiled in only on ppc and sh4, so I'm CCing the
> maintainers for those architectures.

The i82374 device is not useful nor usable on SH4. It has just been
added in commit 85d3846a39 to be able to run the tests.

Aurelien
Eduardo Otubo Sept. 7, 2017, 8:38 a.m. UTC | #5
On Fri, Sep 01, 2017 at 12:44:30PM -0300, Eduardo Habkost wrote:
> On Fri, Sep 01, 2017 at 05:34:34PM +0200, Markus Armbruster wrote:
> > Eduardo Habkost <ehabkost@redhat.com> writes:
> > 
> > > i82374 is compiled in only on ppc and sh4, so I'm CCing the
> > > maintainers for those architectures.
> > >
> > > On Fri, Sep 01, 2017 at 01:03:32PM +0200, Eduardo Otubo wrote:
> > >> When used with the following command line:
> > >> 
> > >>  ./ppc64-softmmu/qemu-system-ppc64 -S -machine 40p,accel=tcg -device i82374
> > >> 
> > >> QEMU with machine type 40p already creates the device i82374. If
> > >> specified in the command line, it will try to create it again, hence
> > >> generating the error.

Well pointed, forgot to describe the actual error. I may inlcude for
the next version of the patch. For for correctness sake, here it is:

 ./ppc64-softmmu/qemu-system-ppc64 -S -machine 40p,accel=tcg -device i82374
 qemu-system-ppc64: hw/isa/isa-bus.c:110: isa_bus_dma: Assertion `!bus->dma[0] && !bus->dma[1]' failed.
 Aborted (core dumped)

> > >
> > > Which error?
> > >
> > >
> > >>                       One way to avoid this problem is to set
> > >> user_creatable=false.
> > >> 
> > >> Signed-off-by: Eduardo Otubo <otubo@redhat.com>
> > >
> > > The patch does more than just avoiding double creation: it
> > > prevents usage of "-device i82374" completely.
> > >
> > > Maybe nobody needs it to work with -device today (would the
> > > device even work?) and it is OK to set user_creatable=false until
> > > we fix the crash.  But we need to be sure of that.
> > >
> > >> ---
> > >>  hw/dma/i82374.c | 1 +
> > >>  1 file changed, 1 insertion(+)
> > >> 
> > >> diff --git a/hw/dma/i82374.c b/hw/dma/i82374.c
> > >> index 6c0f975df0..5275d822e0 100644
> > >> --- a/hw/dma/i82374.c
> > >> +++ b/hw/dma/i82374.c
> > >> @@ -139,6 +139,7 @@ static void i82374_class_init(ObjectClass *klass, void *data)
> > >>      dc->realize = i82374_realize;
> > >>      dc->vmsd = &vmstate_i82374;
> > >>      dc->props = i82374_properties;
> > >> +    dc->user_creatable = false;
> > >
> > > A "Reason:" comment explaining why user_creatable=false is
> > > mandatory.  See the comment above user_creatable declaration in
> > > qdev-core.h for reference.
> > >
> > > I suggest the following:
> > >
> > >     /*
> > >      * Reason: i82374_realize() crashes (assertion failure inside isa_bus_dma()
> > >      *         if the device is instantiated twice.
> > >      */

I agree with the comment above. If there's nothing left to fix/add
I'll just send a v2 for this shortly.

> > 
> > We need to find out *why* it crashes.  Once we know, we can likely write
> > a better comment.
> 
> It crashes because isa_bus_dma() isn't supposed to be called
> twice for the same bus.
> 
> Making isa_bus_dma()/DMA_init()/i82374_realize() return an error
> instead of asserting would be even better than setting
> user_creatable=false.
> 
> -- 
> Eduardo
>
Eduardo Otubo Sept. 7, 2017, 8:38 a.m. UTC | #6
On Sat, Sep 02, 2017 at 11:15:20AM +0200, Aurelien Jarno wrote:
> On 2017-09-01 11:30, Eduardo Habkost wrote:
> > i82374 is compiled in only on ppc and sh4, so I'm CCing the
> > maintainers for those architectures.
> 
> The i82374 device is not useful nor usable on SH4. It has just been
> added in commit 85d3846a39 to be able to run the tests.
> 
> Aurelien
> 

Any word from the ppc guys?
Paolo Bonzini Sept. 7, 2017, 4:05 p.m. UTC | #7
Il 02 set 2017 11:17 AM, "Aurelien Jarno" <aurelien@aurel32.net> ha scritto:

On 2017-09-01 11:30, Eduardo Habkost wrote:
> i82374 is compiled in only on ppc and sh4, so I'm CCing the
> maintainers for those architectures.

The i82374 device is not useful nor usable on SH4. It has just been
added in commit 85d3846a39 to be able to run the tests.


But that means that the patch is wrong and probably was not tested with
"make check".

Eduardo's proposal is the right one.

Paolo


Aurelien

--
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net
Eduardo Otubo Sept. 8, 2017, 7:57 a.m. UTC | #8
On Thu, Sep 07, 2017 at 06:05:37PM +0200, Paolo Bonzini wrote:
> Il 02 set 2017 11:17 AM, "Aurelien Jarno" <aurelien@aurel32.net> ha scritto:
> 
> On 2017-09-01 11:30, Eduardo Habkost wrote:
> > i82374 is compiled in only on ppc and sh4, so I'm CCing the
> > maintainers for those architectures.
> 
> The i82374 device is not useful nor usable on SH4. It has just been
> added in commit 85d3846a39 to be able to run the tests.
> 
> 
> But that means that the patch is wrong and probably was not tested with
> "make check".
> 
> Eduardo's proposal is the right one.
> 

Great, I'll just add the missing details and resend the v2. Thanks for
the review.

Regards,
Eduardo Habkost Sept. 9, 2017, 9:52 p.m. UTC | #9
On Thu, Sep 07, 2017 at 10:38:29AM +0200, Eduardo Otubo wrote:
> On Fri, Sep 01, 2017 at 12:44:30PM -0300, Eduardo Habkost wrote:
> > On Fri, Sep 01, 2017 at 05:34:34PM +0200, Markus Armbruster wrote:
> > > Eduardo Habkost <ehabkost@redhat.com> writes:
> > > > On Fri, Sep 01, 2017 at 01:03:32PM +0200, Eduardo Otubo wrote:
[...]
> > > >> diff --git a/hw/dma/i82374.c b/hw/dma/i82374.c
> > > >> index 6c0f975df0..5275d822e0 100644
> > > >> --- a/hw/dma/i82374.c
> > > >> +++ b/hw/dma/i82374.c
> > > >> @@ -139,6 +139,7 @@ static void i82374_class_init(ObjectClass *klass, void *data)
> > > >>      dc->realize = i82374_realize;
> > > >>      dc->vmsd = &vmstate_i82374;
> > > >>      dc->props = i82374_properties;
> > > >> +    dc->user_creatable = false;
> > > >
> > > > A "Reason:" comment explaining why user_creatable=false is
> > > > mandatory.  See the comment above user_creatable declaration in
> > > > qdev-core.h for reference.
> > > >
> > > > I suggest the following:
> > > >
> > > >     /*
> > > >      * Reason: i82374_realize() crashes (assertion failure inside isa_bus_dma()
> > > >      *         if the device is instantiated twice.
> > > >      */
> 
> I agree with the comment above. If there's nothing left to fix/add
> I'll just send a v2 for this shortly.

I suggest amending it with the additional info below, explaining
that isa_bus_dma() isn't supposed to be called twice, and that we
need to make isa_bus_dma()/DMA_init()/i82374_realize() return an
appropriate error if the device is instantiated twice.


> 
> > > 
> > > We need to find out *why* it crashes.  Once we know, we can likely write
> > > a better comment.
> > 
> > It crashes because isa_bus_dma() isn't supposed to be called
> > twice for the same bus.
> > 
> > Making isa_bus_dma()/DMA_init()/i82374_realize() return an error
> > instead of asserting would be even better than setting
> > user_creatable=false.
> > 
> > -- 
> > Eduardo
> > 
> 
> -- 
> Eduardo Otubo
> Senior Software Engineer @ RedHat

Patch
diff mbox

diff --git a/hw/dma/i82374.c b/hw/dma/i82374.c
index 6c0f975df0..5275d822e0 100644
--- a/hw/dma/i82374.c
+++ b/hw/dma/i82374.c
@@ -139,6 +139,7 @@  static void i82374_class_init(ObjectClass *klass, void *data)
     dc->realize = i82374_realize;
     dc->vmsd = &vmstate_i82374;
     dc->props = i82374_properties;
+    dc->user_creatable = false;
 }
 
 static const TypeInfo i82374_info = {