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hw/xen: Simplify emulated Xen platform init

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I initially put the basic platform init (overlay pages, grant tables,
event channels) into mc->kvm_type because that was the earliest place
that could sensibly test for xen_mode==XEN_EMULATE.

The intent was to do this early enough that we could then initialise the
XenBus and other parts which would have depended on them, from a generic
location for both Xen and KVM/Xen in the PC-specific code, as seen in
https://lore.kernel.org/qemu-devel/20230116221919.1124201-16-dwmw2@infradead.org/

However, then the Xen on Arm patches came along, and *they* wanted to
do the XenBus init from a 'generic' Xen-specific location instead:
https://lore.kernel.org/qemu-devel/20230210222729.957168-4-sstabellini@kernel.org/

Since there's no generic location that covers all three, I conceded to
do it for XEN_EMULATE mode in pc_basic_devices_init().

And now there's absolutely no point in having some of the platform init
done from pc_machine_kvm_type(); we can move it all up to live in a
single place in pc_basic_devices_init(). This has the added benefit that
we can drop the separate xen_evtchn_connect_gsis() function completely,
and pass just the system GSIs in directly to xen_evtchn_create().

While I'm at it, it does no harm to explicitly pass in the *number* of
said GSIs, because it does make me twitch a bit to pass an array of
impicit size. During the lifetime of the KVM/Xen patchset, that had
already changed (albeit just cosmetically) from GSI_NUM_PINS to
IOAPIC_NUM_PINS.

And document a bit better that this is for the *output* GSI for raising
CPU0's events when the per-CPU vector isn't available. The fact that
we create a whole set of them and then only waggle the one we're told
to, instead of having a single output and only *connecting* it to the
GSI that it should be connected to, is still non-intuitive for me.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-Id: <20230412185102.441523-2-dwmw2@infradead.org>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
David Woodhouse 2023-04-12 19:50:58 +01:00 • committed by Anthony PERARD
parent f5e6786de4
commit eeedfe6c63
3 changed files with 25 additions and 31 deletions
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13
hw/i386/pc.c
View file

@ -1332,7 +1332,10 @@ void pc_basic_device_init(struct PCMachineState *pcms,
#ifdef CONFIG_XEN_EMU
if (xen_mode == XEN_EMULATE) {
xen_evtchn_connect_gsis(gsi);
xen_overlay_create();
xen_evtchn_create(IOAPIC_NUM_PINS, gsi);
xen_gnttab_create();
xen_xenstore_create();
if (pcms->bus) {
pci_create_simple(pcms->bus, -1, "xen-platform");
}
@ -1882,14 +1885,6 @@ static void pc_machine_initfn(Object *obj)
int pc_machine_kvm_type(MachineState *machine, const char *kvm_type)
{
#ifdef CONFIG_XEN_EMU
if (xen_mode == XEN_EMULATE) {
xen_overlay_create();
xen_evtchn_create();
xen_gnttab_create();
xen_xenstore_create();
}
#endif
return 0;
}