diff mbox series

[2/3] hw/misc: Add mmio-debug-exit device

Message ID 20220711185640.3558813-3-iii@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series accel/tcg: Fix unaligned stores to s390x low-address-protected lowcore | expand

Commit Message

Ilya Leoshkevich July 11, 2022, 6:56 p.m. UTC 
System tests on x86 use isa-debug-exit device in order to signal
success or failure to the test runner. Unfortunately it's not easily
usable on other architectures, since a guest needs to access
address_space_io, which may not be as straightforward as on x86.
Also, it requires adding ISA bus, which an architecture might not
otherwise need.

Introduce mmio-debug-exit device, which has the same semantics, but is
triggered by writes to memory.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 hw/misc/Kconfig          |  3 ++
 hw/misc/debugexit_mmio.c | 80 ++++++++++++++++++++++++++++++++++++++++
 hw/misc/meson.build      |  1 +
 hw/s390x/Kconfig         |  1 +
 4 files changed, 85 insertions(+)
 create mode 100644 hw/misc/debugexit_mmio.c

Comments

Richard Henderson July 12, 2022, 5:12 a.m. UTC | #1 
On 7/12/22 00:26, Ilya Leoshkevich wrote:
> System tests on x86 use isa-debug-exit device in order to signal
> success or failure to the test runner. Unfortunately it's not easily
> usable on other architectures, since a guest needs to access
> address_space_io, which may not be as straightforward as on x86.
> Also, it requires adding ISA bus, which an architecture might not
> otherwise need.
> 
> Introduce mmio-debug-exit device, which has the same semantics, but is
> triggered by writes to memory.
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

You shouldn't need this for s390x, as there are already (at least) two other paths to 
qemu_system_shutdown_request.

E.g. SIGP, which has a stop option.


r~
Ilya Leoshkevich July 12, 2022, 9:52 a.m. UTC | #2 
On Tue, 2022-07-12 at 10:42 +0530, Richard Henderson wrote:
> On 7/12/22 00:26, Ilya Leoshkevich wrote:
> > System tests on x86 use isa-debug-exit device in order to signal
> > success or failure to the test runner. Unfortunately it's not
> > easily
> > usable on other architectures, since a guest needs to access
> > address_space_io, which may not be as straightforward as on x86.
> > Also, it requires adding ISA bus, which an architecture might not
> > otherwise need.
> > 
> > Introduce mmio-debug-exit device, which has the same semantics, but
> > is
> > triggered by writes to memory.
> > 
> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> 
> You shouldn't need this for s390x, as there are already (at least)
> two other paths to 
> qemu_system_shutdown_request.
> 
> E.g. SIGP, which has a stop option.
> 
> 
> r~
> 

I would normally use lpswe + disabled wait, but this always gives me
exit status code 0, which doesn't allow easily distinguishing between
success and failure.

Code-wise SIGP seems to do roughly the same thing, and a quick
experiment with:

    lgfi %r4,-1
    lgfi %r5,-1
    larl %r6,_cpuaddr
    stap 0(%r6)
    lh %r6,0(%r6)
    nilh %r6,0
    sigp %r4,%r6,5
_cpuaddr: .short 0

confirmed that we get exit status code 0 as well.

Best regards,
Ilya
David Hildenbrand July 12, 2022, 10:08 a.m. UTC | #3 
On 12.07.22 11:52, Ilya Leoshkevich wrote:
> On Tue, 2022-07-12 at 10:42 +0530, Richard Henderson wrote:
>> On 7/12/22 00:26, Ilya Leoshkevich wrote:
>>> System tests on x86 use isa-debug-exit device in order to signal
>>> success or failure to the test runner. Unfortunately it's not
>>> easily
>>> usable on other architectures, since a guest needs to access
>>> address_space_io, which may not be as straightforward as on x86.
>>> Also, it requires adding ISA bus, which an architecture might not
>>> otherwise need.
>>>
>>> Introduce mmio-debug-exit device, which has the same semantics, but
>>> is
>>> triggered by writes to memory.
>>>
>>> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
>>
>> You shouldn't need this for s390x, as there are already (at least)
>> two other paths to 
>> qemu_system_shutdown_request.
>>
>> E.g. SIGP, which has a stop option.
>>
>>
>> r~
>>
> 
> I would normally use lpswe + disabled wait, but this always gives me
> exit status code 0, which doesn't allow easily distinguishing between
> success and failure.
> 
> Code-wise SIGP seems to do roughly the same thing, and a quick
> experiment with:
> 
>     lgfi %r4,-1
>     lgfi %r5,-1
>     larl %r6,_cpuaddr
>     stap 0(%r6)
>     lh %r6,0(%r6)
>     nilh %r6,0
>     sigp %r4,%r6,5
> _cpuaddr: .short 0
> 
> confirmed that we get exit status code 0 as well.

disabled wait should trigger a qemu_system_guest_panicked().

But "panic_action == PANIC_ACTION_SHUTDOWN" seems to only make
qemu_main_loop() return with main_loop_should_exit() == true.

main/qemu_main will always return 0.

We could return != 0 on guest panic, but not sure if that could break
existing scripts. We'd need a new QEMU toggle for that most probably ...
David Hildenbrand July 12, 2022, 10:08 a.m. UTC | #4 
On 12.07.22 11:52, Ilya Leoshkevich wrote:
> On Tue, 2022-07-12 at 10:42 +0530, Richard Henderson wrote:
>> On 7/12/22 00:26, Ilya Leoshkevich wrote:
>>> System tests on x86 use isa-debug-exit device in order to signal
>>> success or failure to the test runner. Unfortunately it's not
>>> easily
>>> usable on other architectures, since a guest needs to access
>>> address_space_io, which may not be as straightforward as on x86.
>>> Also, it requires adding ISA bus, which an architecture might not
>>> otherwise need.
>>>
>>> Introduce mmio-debug-exit device, which has the same semantics, but
>>> is
>>> triggered by writes to memory.
>>>
>>> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
>>
>> You shouldn't need this for s390x, as there are already (at least)
>> two other paths to 
>> qemu_system_shutdown_request.
>>
>> E.g. SIGP, which has a stop option.
>>
>>
>> r~
>>
> 
> I would normally use lpswe + disabled wait, but this always gives me
> exit status code 0, which doesn't allow easily distinguishing between
> success and failure.
> 
> Code-wise SIGP seems to do roughly the same thing, and a quick
> experiment with:
> 
>     lgfi %r4,-1
>     lgfi %r5,-1
>     larl %r6,_cpuaddr
>     stap 0(%r6)
>     lh %r6,0(%r6)
>     nilh %r6,0
>     sigp %r4,%r6,5
> _cpuaddr: .short 0
> 
> confirmed that we get exit status code 0 as well.

disabled wait should trigger a qemu_system_guest_panicked().

But "panic_action == PANIC_ACTION_SHUTDOWN" seems to only make
qemu_main_loop() return with main_loop_should_exit() == true.

main/qemu_main will always return 0.

We could return != 0 on guest panic, but not sure if that could break
existing scripts. We'd need a new QEMU toggle for that most probably ...
Ilya Leoshkevich July 12, 2022, 10:30 a.m. UTC | #5 
On Tue, 2022-07-12 at 12:08 +0200, David Hildenbrand wrote:
> On 12.07.22 11:52, Ilya Leoshkevich wrote:
> > On Tue, 2022-07-12 at 10:42 +0530, Richard Henderson wrote:
> > > On 7/12/22 00:26, Ilya Leoshkevich wrote:
> > > > System tests on x86 use isa-debug-exit device in order to
> > > > signal
> > > > success or failure to the test runner. Unfortunately it's not
> > > > easily
> > > > usable on other architectures, since a guest needs to access
> > > > address_space_io, which may not be as straightforward as on
> > > > x86.
> > > > Also, it requires adding ISA bus, which an architecture might
> > > > not
> > > > otherwise need.
> > > > 
> > > > Introduce mmio-debug-exit device, which has the same semantics,
> > > > but
> > > > is
> > > > triggered by writes to memory.
> > > > 
> > > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> > > 
> > > You shouldn't need this for s390x, as there are already (at
> > > least)
> > > two other paths to 
> > > qemu_system_shutdown_request.
> > > 
> > > E.g. SIGP, which has a stop option.
> > > 
> > > 
> > > r~
> > > 
> > 
> > I would normally use lpswe + disabled wait, but this always gives
> > me
> > exit status code 0, which doesn't allow easily distinguishing
> > between
> > success and failure.
> > 
> > Code-wise SIGP seems to do roughly the same thing, and a quick
> > experiment with:
> > 
> >     lgfi %r4,-1
> >     lgfi %r5,-1
> >     larl %r6,_cpuaddr
> >     stap 0(%r6)
> >     lh %r6,0(%r6)
> >     nilh %r6,0
> >     sigp %r4,%r6,5
> > _cpuaddr: .short 0
> > 
> > confirmed that we get exit status code 0 as well.
> 
> disabled wait should trigger a qemu_system_guest_panicked().
> 
> But "panic_action == PANIC_ACTION_SHUTDOWN" seems to only make
> qemu_main_loop() return with main_loop_should_exit() == true.
> 
> main/qemu_main will always return 0.
> 
> We could return != 0 on guest panic, but not sure if that could break
> existing scripts. We'd need a new QEMU toggle for that most probably
> ...
> 

I wonder if a device is a cleaner way to solve this? It may be used on
all architectures, so there is no need to invent per-architecture way
to exit with a specific code. Maybe we can even replace Intel's
debugexit with it.
diff mbox series

Patch

diff --git a/hw/misc/Kconfig b/hw/misc/Kconfig
index cbabe9f78c..0f12735ef7 100644
--- a/hw/misc/Kconfig
+++ b/hw/misc/Kconfig
@@ -15,6 +15,9 @@  config ISA_DEBUG
     bool
     depends on ISA_BUS
 
+config MMIO_DEBUGEXIT
+    bool
+
 config SGA
     bool
     depends on ISA_BUS
diff --git a/hw/misc/debugexit_mmio.c b/hw/misc/debugexit_mmio.c
new file mode 100644
index 0000000000..5e823cc01c
--- /dev/null
+++ b/hw/misc/debugexit_mmio.c
@@ -0,0 +1,80 @@ 
+/*
+ * Exit with status X when the guest writes X (little-endian) to a specified
+ * address. For testing purposes only.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "exec/address-spaces.h"
+#include "exec/memory.h"
+#include "hw/qdev-core.h"
+#include "hw/qdev-properties.h"
+
+#define TYPE_MMIO_DEBUG_EXIT_DEVICE "mmio-debug-exit"
+OBJECT_DECLARE_SIMPLE_TYPE(MMIODebugExitState, MMIO_DEBUG_EXIT_DEVICE)
+
+struct MMIODebugExitState {
+    DeviceState parent_obj;
+
+    uint32_t base;
+    uint32_t size;
+    MemoryRegion region;
+};
+
+static uint64_t mmio_debug_exit_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0;
+}
+
+static void mmio_debug_exit_write(void *opaque, hwaddr addr, uint64_t val,
+                                  unsigned width)
+{
+    exit(val);
+}
+
+static const MemoryRegionOps mmio_debug_exit_ops = {
+    .read = mmio_debug_exit_read,
+    .write = mmio_debug_exit_write,
+    .valid.min_access_size = 1,
+    .valid.max_access_size = 8,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
+static void mmio_debug_exit_realizefn(DeviceState *d, Error **errp)
+{
+    MMIODebugExitState *s = MMIO_DEBUG_EXIT_DEVICE(d);
+
+    memory_region_init_io(&s->region, OBJECT(s), &mmio_debug_exit_ops, s,
+                          TYPE_MMIO_DEBUG_EXIT_DEVICE, s->size);
+    memory_region_add_subregion(get_system_memory(), s->base, &s->region);
+}
+
+static Property mmio_debug_exit_properties[] = {
+    DEFINE_PROP_UINT32("base", MMIODebugExitState, base, 0),
+    DEFINE_PROP_UINT32("size", MMIODebugExitState, size, 1),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void mmio_debug_exit_class_initfn(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = mmio_debug_exit_realizefn;
+    device_class_set_props(dc, mmio_debug_exit_properties);
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+}
+
+static const TypeInfo mmio_debug_exit_info = {
+    .name          = TYPE_MMIO_DEBUG_EXIT_DEVICE,
+    .parent        = TYPE_DEVICE,
+    .instance_size = sizeof(MMIODebugExitState),
+    .class_init    = mmio_debug_exit_class_initfn,
+};
+
+static void mmio_debug_exit_register_types(void)
+{
+    type_register_static(&mmio_debug_exit_info);
+}
+
+type_init(mmio_debug_exit_register_types)
diff --git a/hw/misc/meson.build b/hw/misc/meson.build
index 95268eddc0..1d2a1067dc 100644
--- a/hw/misc/meson.build
+++ b/hw/misc/meson.build
@@ -2,6 +2,7 @@  softmmu_ss.add(when: 'CONFIG_APPLESMC', if_true: files('applesmc.c'))
 softmmu_ss.add(when: 'CONFIG_EDU', if_true: files('edu.c'))
 softmmu_ss.add(when: 'CONFIG_FW_CFG_DMA', if_true: files('vmcoreinfo.c'))
 softmmu_ss.add(when: 'CONFIG_ISA_DEBUG', if_true: files('debugexit.c'))
+softmmu_ss.add(when: 'CONFIG_MMIO_DEBUGEXIT', if_true: files('debugexit_mmio.c'))
 softmmu_ss.add(when: 'CONFIG_ISA_TESTDEV', if_true: files('pc-testdev.c'))
 softmmu_ss.add(when: 'CONFIG_PCA9552', if_true: files('pca9552.c'))
 softmmu_ss.add(when: 'CONFIG_PCI_TESTDEV', if_true: files('pci-testdev.c'))
diff --git a/hw/s390x/Kconfig b/hw/s390x/Kconfig
index 5e7d8a2bae..9223715dcc 100644
--- a/hw/s390x/Kconfig
+++ b/hw/s390x/Kconfig
@@ -5,6 +5,7 @@  config S390_CCW_VIRTIO
     imply VFIO_AP
     imply VFIO_CCW
     imply WDT_DIAG288
+    imply MMIO_DEBUGEXIT
     select PCI
     select S390_FLIC
     select SCLPCONSOLE