[Qemu-devel] [PATCH 0/1] pc-bios/s390-ccw.img build fix for 2.7

[Qemu-devel] [PATCH 0/1] pc-bios/s390-ccw.img build fix for 2.7

[Christian Borntraeger]

This was done pretty quickly, so some review would be nice.
If OK, I think this should go via Conny for 2.7.

Christian Borntraeger (1):
  pc-bios/s390-ccw.img: Fix build

 pc-bios/s390-ccw/Makefile | 6 ++++--
 pc-bios/s390-ccw/virtio.c | 7 ++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

-- 
2.5.5

[Qemu-devel] [PATCH 1/1] pc-bios/s390-ccw.img: Fix build

[Christian Borntraeger]

Since
commit a9c87304b76d ("build-sys: fix building with make CFLAGS=.. argument")

pc-bios/s390-ccw.img build might fail with

--- snip ---
main.o: In function `virtio_setup':
qemu/pc-bios/s390-ccw/main.c:117: undefined reference to `__stack_chk_fail'
--- snip ---

Changing the CFLAGS to QEMU_CFLAGS does the trick.

We also need to fix a potential aliasing bug as we now compile with
-O2 instead of -O0. This was the warning message:

--- snip ---
/home/cborntra/REPOS/qemu/pc-bios/s390-ccw/virtio.c:64:5: error:
dereferencing type-punned pointer will break strict-aliasing rules
[-Werror=strict-aliasing]
     return kvm_hypercall(KVM_S390_VIRTIO_CCW_NOTIFY, *(u32 *)&schid,
--- snip ---

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 pc-bios/s390-ccw/Makefile | 6 ++++--
 pc-bios/s390-ccw/virtio.c | 7 ++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
index 4208cb4..a9dcca4 100644
--- a/pc-bios/s390-ccw/Makefile
+++ b/pc-bios/s390-ccw/Makefile
@@ -10,8 +10,10 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
 .PHONY : all clean build-all
 
 OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o virtio-scsi.o
-CFLAGS += -fPIE -fno-stack-protector -ffreestanding -march=z900
-CFLAGS += -fno-delete-null-pointer-checks -msoft-float
+QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
+QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
+QEMU_CFLAGS += -march=z900 -fPIE
+QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
 LDFLAGS += -Wl,-pie -nostdlib
 
 build-all: s390-ccw.img
diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
index 1d34e8c..9a7681d 100644
--- a/pc-bios/s390-ccw/virtio.c
+++ b/pc-bios/s390-ccw/virtio.c
@@ -61,7 +61,12 @@ static long kvm_hypercall(unsigned long nr, unsigned long param1,
 
 static long virtio_notify(SubChannelId schid, int vq_idx, long cookie)
 {
-    return kvm_hypercall(KVM_S390_VIRTIO_CCW_NOTIFY, *(u32 *)&schid,
+    union {
+        SubChannelId schid;
+        u32 value;
+    } sch;
+    sch.schid = schid;
+    return kvm_hypercall(KVM_S390_VIRTIO_CCW_NOTIFY, sch.value,
                          vq_idx, cookie);
 }
 
-- 
2.5.5

Re: [Qemu-devel] [PATCH 1/1] pc-bios/s390-ccw.img: Fix build

[Cornelia Huck]

On Mon, 15 Aug 2016 12:28:11 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> Since
> commit a9c87304b76d ("build-sys: fix building with make CFLAGS=.. argument")
> 
> pc-bios/s390-ccw.img build might fail with
> 
> --- snip ---
> main.o: In function `virtio_setup':
> qemu/pc-bios/s390-ccw/main.c:117: undefined reference to `__stack_chk_fail'
> --- snip ---
> 
> Changing the CFLAGS to QEMU_CFLAGS does the trick.
> 
> We also need to fix a potential aliasing bug as we now compile with
> -O2 instead of -O0. This was the warning message:
> 
> --- snip ---
> /home/cborntra/REPOS/qemu/pc-bios/s390-ccw/virtio.c:64:5: error:
> dereferencing type-punned pointer will break strict-aliasing rules
> [-Werror=strict-aliasing]

Can we preserve no strict aliasing somehow? I don't really want to
change the bios code at that point if not needed.

>      return kvm_hypercall(KVM_S390_VIRTIO_CCW_NOTIFY, *(u32 *)&schid,
> --- snip ---
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  pc-bios/s390-ccw/Makefile | 6 ++++--
>  pc-bios/s390-ccw/virtio.c | 7 ++++++-
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
> index 4208cb4..a9dcca4 100644
> --- a/pc-bios/s390-ccw/Makefile
> +++ b/pc-bios/s390-ccw/Makefile
> @@ -10,8 +10,10 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
>  .PHONY : all clean build-all
> 
>  OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o virtio-scsi.o
> -CFLAGS += -fPIE -fno-stack-protector -ffreestanding -march=z900
> -CFLAGS += -fno-delete-null-pointer-checks -msoft-float
> +QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
> +QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
> +QEMU_CFLAGS += -march=z900 -fPIE
> +QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
>  LDFLAGS += -Wl,-pie -nostdlib

Does not look unreasonable, but as I've lost myself in the makefile
dependencies before, I'd like another review.

[Qemu-devel] [PATCH v2 1/1] pc-bios/s390-ccw.img: Fix build

[Christian Borntraeger]

Since
commit a9c87304b76d ("build-sys: fix building with make CFLAGS=.. argument")

pc-bios/s390-ccw.img build might fail with

--- snip ---
main.o: In function `virtio_setup':
qemu/pc-bios/s390-ccw/main.c:117: undefined reference to `__stack_chk_fail'
--- snip ---

Changing the CFLAGS to QEMU_CFLAGS does the trick. We also need to
add -fno-strict-aliasing as this was filtered out.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
V1->V2: use fno-strict-aliasing instead of changing the code
 pc-bios/s390-ccw/Makefile | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
index 4208cb4..0ab2538 100644
--- a/pc-bios/s390-ccw/Makefile
+++ b/pc-bios/s390-ccw/Makefile
@@ -10,8 +10,10 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
 .PHONY : all clean build-all
 
 OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o virtio-scsi.o
-CFLAGS += -fPIE -fno-stack-protector -ffreestanding -march=z900
-CFLAGS += -fno-delete-null-pointer-checks -msoft-float
+QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
+QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
+QEMU_CFLAGS += -march=z900 -fPIE -fno-strict-aliasing
+QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
 LDFLAGS += -Wl,-pie -nostdlib
 
 build-all: s390-ccw.img
-- 
2.5.5

Re: [Qemu-devel] [PATCH v2 1/1] pc-bios/s390-ccw.img: Fix build

[Cornelia Huck]

On Mon, 15 Aug 2016 13:03:17 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> Since
> commit a9c87304b76d ("build-sys: fix building with make CFLAGS=.. argument")
> 
> pc-bios/s390-ccw.img build might fail with
> 
> --- snip ---
> main.o: In function `virtio_setup':
> qemu/pc-bios/s390-ccw/main.c:117: undefined reference to `__stack_chk_fail'
> --- snip ---
> 
> Changing the CFLAGS to QEMU_CFLAGS does the trick. We also need to
> add -fno-strict-aliasing as this was filtered out.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> V1->V2: use fno-strict-aliasing instead of changing the code
>  pc-bios/s390-ccw/Makefile | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Thanks, applied.

Re: [Qemu-devel] [PATCH v2 1/1] pc-bios/s390-ccw.img: Fix build

[Paolo Bonzini]

On 15/08/2016 13:03, Christian Borntraeger wrote:
> Since
> commit a9c87304b76d ("build-sys: fix building with make CFLAGS=.. argument")
> 
> pc-bios/s390-ccw.img build might fail with
> 
> --- snip ---
> main.o: In function `virtio_setup':
> qemu/pc-bios/s390-ccw/main.c:117: undefined reference to `__stack_chk_fail'
> --- snip ---
> 
> Changing the CFLAGS to QEMU_CFLAGS does the trick. We also need to
> add -fno-strict-aliasing as this was filtered out.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> V1->V2: use fno-strict-aliasing instead of changing the code
>  pc-bios/s390-ccw/Makefile | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
> index 4208cb4..0ab2538 100644
> --- a/pc-bios/s390-ccw/Makefile
> +++ b/pc-bios/s390-ccw/Makefile
> @@ -10,8 +10,10 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
>  .PHONY : all clean build-all
>  
>  OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o virtio-scsi.o
> -CFLAGS += -fPIE -fno-stack-protector -ffreestanding -march=z900
> -CFLAGS += -fno-delete-null-pointer-checks -msoft-float
> +QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
> +QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
> +QEMU_CFLAGS += -march=z900 -fPIE -fno-strict-aliasing
> +QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
>  LDFLAGS += -Wl,-pie -nostdlib
>  
>  build-all: s390-ccw.img
> 

Looks pretty much like pc-bios/optionrom/Makefile with respect to C
compiler flags.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Re: [Qemu-devel] [PATCH v2 1/1] pc-bios/s390-ccw.img: Fix build

[Cornelia Huck]

On Wed, 17 Aug 2016 12:57:47 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 15/08/2016 13:03, Christian Borntraeger wrote:
> > Since
> > commit a9c87304b76d ("build-sys: fix building with make CFLAGS=.. argument")
> > 
> > pc-bios/s390-ccw.img build might fail with
> > 
> > --- snip ---
> > main.o: In function `virtio_setup':
> > qemu/pc-bios/s390-ccw/main.c:117: undefined reference to `__stack_chk_fail'
> > --- snip ---
> > 
> > Changing the CFLAGS to QEMU_CFLAGS does the trick. We also need to
> > add -fno-strict-aliasing as this was filtered out.
> > 
> > Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> > ---
> > V1->V2: use fno-strict-aliasing instead of changing the code
> >  pc-bios/s390-ccw/Makefile | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
> > index 4208cb4..0ab2538 100644
> > --- a/pc-bios/s390-ccw/Makefile
> > +++ b/pc-bios/s390-ccw/Makefile
> > @@ -10,8 +10,10 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
> >  .PHONY : all clean build-all
> >  
> >  OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o virtio-scsi.o
> > -CFLAGS += -fPIE -fno-stack-protector -ffreestanding -march=z900
> > -CFLAGS += -fno-delete-null-pointer-checks -msoft-float
> > +QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
> > +QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
> > +QEMU_CFLAGS += -march=z900 -fPIE -fno-strict-aliasing
> > +QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
> >  LDFLAGS += -Wl,-pie -nostdlib
> >  
> >  build-all: s390-ccw.img
> > 
> 
> Looks pretty much like pc-bios/optionrom/Makefile with respect to C
> compiler flags.
> 
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Yes, that's also what I thought, so I already pushed it upstream :)

Still, thanks for the review!