| Message ID | 20240305191312.321127-1-marmarek@invisiblethingslab.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] hw/xen: detect when running inside stubdomain | expand |
On Tue, Mar 5, 2024 at 2:13 PM Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> wrote: > > Introduce global xen_is_stubdomain variable when qemu is running inside > a stubdomain instead of dom0. This will be relevant for subsequent > patches, as few things like accessing PCI config space need to be done > differently. > > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Reviewed-by: Jason Andryuk <jandryuk@gmail.com>
On Tue, Mar 05, 2024 at 08:12:29PM +0100, Marek Marczykowski-Górecki wrote: > diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c > index 124dd5f3d6..6bd4e6eb2f 100644 > --- a/hw/xen/xen-legacy-backend.c > +++ b/hw/xen/xen-legacy-backend.c > @@ -603,6 +603,20 @@ static void xen_set_dynamic_sysbus(void) > machine_class_allow_dynamic_sysbus_dev(mc, TYPE_XENSYSDEV); > } > > +static bool xen_check_stubdomain(void) > +{ > + char *dm_path = g_strdup_printf("/local/domain/%d/image", xen_domid); > + int32_t dm_domid; > + bool is_stubdom = false; > + > + if (!xenstore_read_int(dm_path, "device-model-domid", &dm_domid)) { > + is_stubdom = dm_domid != 0; > + } > + > + g_free(dm_path); > + return is_stubdom; > +} > + > void xen_be_init(void) > { > xenstore = qemu_xen_xs_open(); > @@ -616,6 +630,8 @@ void xen_be_init(void) > exit(1); > } > > + xen_is_stubdomain = xen_check_stubdomain(); This isn't really a backend specific information, and xen_be_init() is all about old backend implementation support. (qdisk which have been the first to be rewritten doesn't need xen_be_init(), or shouldn't). Could we move the initialisation elsewhere? Is this relevant PV guests? If not, we could move the initialisation to xen_hvm_init_pc(). Also, avoid having xen_check_stubdomain() depending on "xen-legacy-backend", if possible. (In xen_hvm_init_pc(), a call to xen_register_ioreq() opens another xenstore, as `state->xenstore`.) (There's already been effort to build QEMU without legacy backends, that stubdom check would break in this scenario.) Thanks,
On Tue, Mar 26, 2024 at 05:06:50PM +0000, Anthony PERARD wrote: > On Tue, Mar 05, 2024 at 08:12:29PM +0100, Marek Marczykowski-Górecki wrote: > > diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c > > index 124dd5f3d6..6bd4e6eb2f 100644 > > --- a/hw/xen/xen-legacy-backend.c > > +++ b/hw/xen/xen-legacy-backend.c > > @@ -603,6 +603,20 @@ static void xen_set_dynamic_sysbus(void) > > machine_class_allow_dynamic_sysbus_dev(mc, TYPE_XENSYSDEV); > > } > > > > +static bool xen_check_stubdomain(void) > > +{ > > + char *dm_path = g_strdup_printf("/local/domain/%d/image", xen_domid); > > + int32_t dm_domid; > > + bool is_stubdom = false; > > + > > + if (!xenstore_read_int(dm_path, "device-model-domid", &dm_domid)) { > > + is_stubdom = dm_domid != 0; > > + } > > + > > + g_free(dm_path); > > + return is_stubdom; > > +} > > + > > void xen_be_init(void) > > { > > xenstore = qemu_xen_xs_open(); > > @@ -616,6 +630,8 @@ void xen_be_init(void) > > exit(1); > > } > > > > + xen_is_stubdomain = xen_check_stubdomain(); > > This isn't really a backend specific information, and xen_be_init() is > all about old backend implementation support. (qdisk which have been the > first to be rewritten doesn't need xen_be_init(), or shouldn't). Could > we move the initialisation elsewhere? I can try to move it, sure. > Is this relevant PV guests? If not, we could move the initialisation to > xen_hvm_init_pc(). > > Also, avoid having xen_check_stubdomain() depending on > "xen-legacy-backend", if possible. > > (In xen_hvm_init_pc(), a call to xen_register_ioreq() opens another > xenstore, as `state->xenstore`.) And xen_register_ioreq() calls xen_be_init() anyway, so it wouldn't change much in practice (at least for now)... > (There's already been effort to build QEMU without legacy backends, that > stubdom check would break in this scenario.)
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c index 124dd5f3d6..6bd4e6eb2f 100644 --- a/hw/xen/xen-legacy-backend.c +++ b/hw/xen/xen-legacy-backend.c @@ -603,6 +603,20 @@ static void xen_set_dynamic_sysbus(void) machine_class_allow_dynamic_sysbus_dev(mc, TYPE_XENSYSDEV); } +static bool xen_check_stubdomain(void) +{ + char *dm_path = g_strdup_printf("/local/domain/%d/image", xen_domid); + int32_t dm_domid; + bool is_stubdom = false; + + if (!xenstore_read_int(dm_path, "device-model-domid", &dm_domid)) { + is_stubdom = dm_domid != 0; + } + + g_free(dm_path); + return is_stubdom; +} + void xen_be_init(void) { xenstore = qemu_xen_xs_open(); @@ -616,6 +630,8 @@ void xen_be_init(void) exit(1); } + xen_is_stubdomain = xen_check_stubdomain(); + xen_sysdev = qdev_new(TYPE_XENSYSDEV); sysbus_realize_and_unref(SYS_BUS_DEVICE(xen_sysdev), &error_fatal); xen_sysbus = qbus_new(TYPE_XENSYSBUS, xen_sysdev, "xen-sysbus"); diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h index 37ecc91fc3..ecb89ecfc1 100644 --- a/include/hw/xen/xen.h +++ b/include/hw/xen/xen.h @@ -36,6 +36,7 @@ enum xen_mode { extern uint32_t xen_domid; extern enum xen_mode xen_mode; extern bool xen_domid_restrict; +extern bool xen_is_stubdomain; int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num); int xen_set_pci_link_route(uint8_t link, uint8_t irq); diff --git a/system/globals.c b/system/globals.c index b6d4e72530..ac27d88bd4 100644 --- a/system/globals.c +++ b/system/globals.c @@ -62,6 +62,7 @@ bool qemu_uuid_set; uint32_t xen_domid; enum xen_mode xen_mode = XEN_DISABLED; bool xen_domid_restrict; +bool xen_is_stubdomain; struct evtchn_backend_ops *xen_evtchn_ops; struct gnttab_backend_ops *xen_gnttab_ops; struct foreignmem_backend_ops *xen_foreignmem_ops;
Introduce global xen_is_stubdomain variable when qemu is running inside a stubdomain instead of dom0. This will be relevant for subsequent patches, as few things like accessing PCI config space need to be done differently. Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> --- Changes in v2: - use sigend int for domid to match xenstore_read_int() types, domid is in a signed range anyway - fix code style --- hw/xen/xen-legacy-backend.c | 16 ++++++++++++++++ include/hw/xen/xen.h | 1 + system/globals.c | 1 + 3 files changed, 18 insertions(+)