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Re: [PATCH v3 1/1] hw/s390x: modularize virtio-gpu-ccw
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From: |
Eduardo Habkost |
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Subject: |
Re: [PATCH v3 1/1] hw/s390x: modularize virtio-gpu-ccw |
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Date: |
Fri, 5 Mar 2021 16:46:03 -0500 |
On Tue, Mar 02, 2021 at 06:35:44PM +0100, Halil Pasic wrote:
> Since the virtio-gpu-ccw device depends on the hw-display-virtio-gpu
> module, which provides the type virtio-gpu-device, packaging the
> hw-display-virtio-gpu module as a separate package that may or may not
> be installed along with the qemu package leads to problems. Namely if
> the hw-display-virtio-gpu is absent, qemu continues to advertise
> virtio-gpu-ccw, but it aborts not only when one attempts using
> virtio-gpu-ccw, but also when libvirtd's capability probing tries
> to instantiate the type to introspect it.
>
> Let us thus introduce a module named hw-s390x-virtio-gpu-ccw that
> is going to provide the virtio-gpu-ccw device. The hw-s390x prefix
> was chosen because it is not a portable device. Because registering
> virtio-gpu-ccw would make non-s390x emulator fail due to a missing
> parent type, if built as a module, before registering it, we check
> if the ancestor types are already registered.
I don't understand what makes it necessary to make the
type_register() call conditional. Calling type_register() before
the parent types are registered is perfectly valid.
I don't think we should prevent type_register() from being
called. We just need to prevent type_initialize() from being
called unless the type definition is complete. This way there
won't be any tricky module loading order requirements.
>
> With virtio-gpu-ccw built as a module, the correct way to package a
> modularized qemu is to require that hw-display-virtio-gpu must be
> installed whenever the module hw-s390x-virtio-gpu-ccw.
>
> The definition S390_ADAPTER_SUPPRESSIBLE was moved to "cpu.h", per
> suggestion of Thomas Huth. From interface design perspective, IMHO, not
> a good thing as it belongs to the public interface of
> css_register_io_adapters(). We did this because CONFIG_KVM requeires
> NEED_CPU_H and Thomas, and other commenters did not like the
> consequences of that.
>
> Moving the interrupt related declarations to s390_flic.h was suggested
> by Cornelia Huck.
>
> Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> ---
>
> As explained in [1] the previous idea of type_register_mayfail() does
> not work. The next best thing is to check if all types we need are
> already registered before registering virtio-gpu-ccw from the module. It
> is reasonable to assume that when the module is loaded, the ancestors
> are already registered (which is not the case if the device is a
> built in one).
>
> The alternatives to this approch I could identify are:
> * A poor mans version of this which checks for the parent
> * Emulator specific modules:
> * An emulator specific directory within the modules directory which
> is ignored by the other emulators.
> * A way to tell the shared util library the name of this directory,
> and the code to check it if set.
> * Build hw-s390x-virtio-gpu-ccw so it lands in this special directory
> in the build tree, and install it there as well.
> I've spend some time with looking into this, but I came to the
> conclusion that the two latter points look hairy.
>
> [1]
> https://lore.kernel.org/qemu-devel/20210222125548.346166-1-pasic@linux.ibm.com/T/#maf0608df5479f87b23606f01f732740d2617b458
> ---
> hw/s390x/meson.build | 7 ++++-
> hw/s390x/virtio-ccw-gpu.c | 5 ++++
> include/hw/s390x/css.h | 7 -----
> include/hw/s390x/s390_flic.h | 3 +++
> include/qom/object.h | 10 ++++++++
> qom/object.c | 50 ++++++++++++++++++++++++++++++++++++
> target/s390x/cpu.h | 9 ++++---
> util/module.c | 1 +
> 8 files changed, 81 insertions(+), 11 deletions(-)
I suggest splitting the QOM core changes and s390x-specific
changes into separate patches, so they can be reviewed and
included separately.
>
> diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
> index 2a7818d94b..7ac972afcf 100644
> --- a/hw/s390x/meson.build
> +++ b/hw/s390x/meson.build
> @@ -34,7 +34,6 @@ virtio_ss.add(files('virtio-ccw.c'))
> virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true:
> files('virtio-ccw-balloon.c'))
> virtio_ss.add(when: 'CONFIG_VIRTIO_BLK', if_true: files('virtio-ccw-blk.c'))
> virtio_ss.add(when: 'CONFIG_VIRTIO_CRYPTO', if_true:
> files('virtio-ccw-crypto.c'))
> -virtio_ss.add(when: 'CONFIG_VIRTIO_GPU', if_true: files('virtio-ccw-gpu.c'))
> virtio_ss.add(when: 'CONFIG_VIRTIO_INPUT', if_true:
> files('virtio-ccw-input.c'))
> virtio_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio-ccw-net.c'))
> virtio_ss.add(when: 'CONFIG_VIRTIO_RNG', if_true: files('virtio-ccw-rng.c'))
> @@ -46,3 +45,9 @@ virtio_ss.add(when: 'CONFIG_VHOST_USER_FS', if_true:
> files('vhost-user-fs-ccw.c'
> s390x_ss.add_all(when: 'CONFIG_VIRTIO_CCW', if_true: virtio_ss)
>
> hw_arch += {'s390x': s390x_ss}
> +
> +hw_s390x_modules = {}
> +virtio_gpu_ccw_ss = ss.source_set()
> +virtio_gpu_ccw_ss.add(when: 'CONFIG_VIRTIO_GPU', if_true:
> [files('virtio-ccw-gpu.c'), pixman])
> +hw_s390x_modules += {'virtio-gpu-ccw': virtio_gpu_ccw_ss}
> +modules += {'hw-s390x': hw_s390x_modules}
> diff --git a/hw/s390x/virtio-ccw-gpu.c b/hw/s390x/virtio-ccw-gpu.c
> index c301e2586b..ccdf6ac20f 100644
> --- a/hw/s390x/virtio-ccw-gpu.c
> +++ b/hw/s390x/virtio-ccw-gpu.c
> @@ -62,6 +62,11 @@ static const TypeInfo virtio_ccw_gpu = {
>
> static void virtio_ccw_gpu_register(void)
> {
> +#ifdef CONFIG_MODULES
> + if (!type_ancestors_registered(&virtio_ccw_gpu)) {
> + return;
> + }
> +#endif
> type_register_static(&virtio_ccw_gpu);
> }
>
> diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
> index 08c869ab0a..7858666307 100644
> --- a/include/hw/s390x/css.h
> +++ b/include/hw/s390x/css.h
> @@ -12,7 +12,6 @@
> #ifndef CSS_H
> #define CSS_H
>
> -#include "cpu.h"
> #include "hw/s390x/adapter.h"
> #include "hw/s390x/s390_flic.h"
> #include "hw/s390x/ioinst.h"
> @@ -233,12 +232,6 @@ uint32_t css_get_adapter_id(CssIoAdapterType type,
> uint8_t isc);
> void css_register_io_adapters(CssIoAdapterType type, bool swap, bool
> maskable,
> uint8_t flags, Error **errp);
>
> -#ifndef CONFIG_KVM
> -#define S390_ADAPTER_SUPPRESSIBLE 0x01
> -#else
> -#define S390_ADAPTER_SUPPRESSIBLE KVM_S390_ADAPTER_SUPPRESSIBLE
> -#endif
> -
> #ifndef CONFIG_USER_ONLY
> SubchDev *css_find_subch(uint8_t m, uint8_t cssid, uint8_t ssid,
> uint16_t schid);
> diff --git a/include/hw/s390x/s390_flic.h b/include/hw/s390x/s390_flic.h
> index e91b15d2d6..3907a13d07 100644
> --- a/include/hw/s390x/s390_flic.h
> +++ b/include/hw/s390x/s390_flic.h
> @@ -134,6 +134,9 @@ void s390_flic_init(void);
> S390FLICState *s390_get_flic(void);
> QEMUS390FLICState *s390_get_qemu_flic(S390FLICState *fs);
> S390FLICStateClass *s390_get_flic_class(S390FLICState *fs);
> +void s390_crw_mchk(void);
> +void s390_io_interrupt(uint16_t subchannel_id, uint16_t subchannel_nr,
> + uint32_t io_int_parm, uint32_t io_int_word);
> bool ais_needed(void *opaque);
>
> #endif /* HW_S390_FLIC_H */
> diff --git a/include/qom/object.h b/include/qom/object.h
> index 6721cd312e..7aa996a042 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -815,6 +815,16 @@ ObjectClass *object_get_class(Object *obj);
> */
> const char *object_get_typename(const Object *obj);
>
> +/**
> + * type_ancestors_registered:
> + * @info: The #TypeInfo of the type
> + *
> + * Returns: true if all the ancestor types, that is classes and interfaces
> this
> + * type inherits form are all already registered, false if there is an
> ancestor
> + * that ain't registered yet
> + */
> +bool type_ancestors_registered(const TypeInfo *info);
> +
> /**
> * type_register_static:
> * @info: The #TypeInfo of the new type.
> diff --git a/qom/object.c b/qom/object.c
> index 491823db4a..03bd9aa2ba 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -281,6 +281,56 @@ static void object_property_free(gpointer data)
> g_free(prop);
> }
>
> +static TypeImpl *type_get_parent_const(const TypeImpl *ti)
> +{
> + return ti->parent_type ? ti->parent_type : type_get_by_name(ti->parent);
> +}
> +
> +
> +static bool __type_ancestors_registered(const TypeImpl *ti)
> +{
> + TypeImpl *parent;
> + int i;
> +
> + if (!ti) {
> + return false;
> + }
> +
> + if (ti->class) {
> + /* fully initialized */
> + return true;
> + }
> +
> + for (i = 0; i < ti->num_interfaces; i++) {
> + if (!type_get_by_name(ti->interfaces[i].typename)) {
> + return false;
> + }
> + }
> + if (ti->parent) {
> + parent = type_get_parent_const(ti);
> + if (!parent) {
> + return false;
> + }
> + return __type_ancestors_registered(parent);
> + }
> + return true;
> +}
> +
> +bool type_ancestors_registered(const TypeInfo *info)
> +{
> + int i;
> +
> + for (i = 0; info->interfaces && info->interfaces[i].type; i++) {
> + if (!type_get_by_name(info->interfaces[i].type)) {
> + return false;
> + }
> + }
> + if (info->parent) {
> + return __type_ancestors_registered(type_get_by_name(info->parent));
> + }
> + return true;
> +}
> +
> static void type_initialize(TypeImpl *ti)
> {
> TypeImpl *parent;
> diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> index 60d434d5ed..b434b905c0 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -40,6 +40,12 @@
>
> #define S390_MAX_CPUS 248
>
> +#ifndef CONFIG_KVM
> +#define S390_ADAPTER_SUPPRESSIBLE 0x01
> +#else
> +#define S390_ADAPTER_SUPPRESSIBLE KVM_S390_ADAPTER_SUPPRESSIBLE
> +#endif
> +
> typedef struct PSW {
> uint64_t mask;
> uint64_t addr;
> @@ -806,9 +812,6 @@ int cpu_s390x_signal_handler(int host_signum, void
> *pinfo, void *puc);
>
>
> /* interrupt.c */
> -void s390_crw_mchk(void);
> -void s390_io_interrupt(uint16_t subchannel_id, uint16_t subchannel_nr,
> - uint32_t io_int_parm, uint32_t io_int_word);
> #define RA_IGNORED 0
> void s390_program_interrupt(CPUS390XState *env, uint32_t code, uintptr_t ra);
> /* service interrupts are floating therefore we must not pass an cpustate */
> diff --git a/util/module.c b/util/module.c
> index c65060c167..cbe89fede6 100644
> --- a/util/module.c
> +++ b/util/module.c
> @@ -304,6 +304,7 @@ static struct {
> { "virtio-gpu-pci-base", "hw-", "display-virtio-gpu-pci" },
> { "virtio-gpu-pci", "hw-", "display-virtio-gpu-pci" },
> { "vhost-user-gpu-pci", "hw-", "display-virtio-gpu-pci" },
> + { "virtio-gpu-ccw", "hw-", "s390x-virtio-gpu-ccw" },
> { "virtio-vga-base", "hw-", "display-virtio-vga" },
> { "virtio-vga", "hw-", "display-virtio-vga" },
> { "vhost-user-vga", "hw-", "display-virtio-vga" },
>
> base-commit: 1af5629673bb5c1592d993f9fb6119a62845f576
> --
> 2.25.1
>
--
Eduardo