From: Paul Durrant <xadimgnik@gmail.com>
To: David Woodhouse <dwmw2@infradead.org>, qemu-devel@nongnu.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Joao Martins" <joao.m.martins@oracle.com>,
"Ankur Arora" <ankur.a.arora@oracle.com>,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
"Thomas Huth" <thuth@redhat.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Juan Quintela" <quintela@redhat.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
"Claudio Fontana" <cfontana@suse.de>
Subject: Re: [RFC PATCH v2 20/22] i386/xen: HVMOP_set_param / HVM_PARAM_CALLBACK_IRQ
Date: Tue, 20 Dec 2022 17:25:31 +0000 [thread overview]
Message-ID: <f9a2d62c-8a09-7e46-6435-8ba379e95a5c@xen.org> (raw)
In-Reply-To: <B09974FC-9E61-4D7E-BFFF-4B2DB9C09AB4@infradead.org>
On 20/12/2022 16:27, David Woodhouse wrote:
>
>
> On 20 December 2022 13:56:39 GMT, Paul Durrant <xadimgnik@gmail.com> wrote:
>> The callback via is essentially just another line interrupt but its assertion is closely coupled with the vcpu upcall_pending bit. Because that is being dealt with in-kernel then the via should be dealt with in-kernel, right?
>
> Not right now, because there's not a lot of point in kernel acceleration in the case that it's delivered as GSI. There's no per-vCPU delivery, so it doesn't get used for IPI, for timers. None of the stuff we want to accelerate in-kernel. Only the actual PV drivers.
>
> If we do FIFO event channels in the future then the kernel will probably need to own those; they need spinlocks and you can have *both* userspace and kernel delivering with test-and-set-bit sequences like you can with 2level.
>
> Even so, I was tempted to add a VFIO-like eventfd pair for the vCPU0 evtchn_upcall_pending and let the kernel drive it... but qemu doesn't even do the EOI side of that as $DEITY intended, so I didn't.
My point was that clearing upcall_pending is essentially the equivalent
of EOI-at-device i.e. it's the thing that drops the line. So, without
some form of interception, we need some way to check it at an
appropriate time... and as you say, there may be no exit to VMM for EOI
of the APIC. So when?
Paul
next prev parent reply other threads:[~2022-12-20 18:44 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-09 9:55 [RFC PATCH v2 00/22] Xen HVM support under KVM David Woodhouse
2022-12-09 9:55 ` [RFC PATCH v2 01/22] include: import xen public headers David Woodhouse
2022-12-12 9:17 ` Paul Durrant
2022-12-09 9:55 ` [RFC PATCH v2 02/22] xen: add CONFIG_XENFV_MACHINE and CONFIG_XEN_EMU options for Xen emulation David Woodhouse
2022-12-12 9:19 ` Paul Durrant
2022-12-12 17:07 ` Paolo Bonzini
2022-12-12 22:22 ` David Woodhouse
2022-12-13 0:39 ` Paolo Bonzini
2022-12-13 0:59 ` David Woodhouse
2022-12-13 22:32 ` Paolo Bonzini
2022-12-16 8:40 ` David Woodhouse
2022-12-09 9:55 ` [RFC PATCH v2 03/22] i386/xen: Add xen-version machine property and init KVM Xen support David Woodhouse
2022-12-12 12:48 ` Paul Durrant
2022-12-12 17:30 ` Paolo Bonzini
2022-12-12 17:55 ` Paul Durrant
2022-12-13 0:13 ` David Woodhouse
2023-01-17 13:49 ` David Woodhouse
2022-12-09 9:55 ` [RFC PATCH v2 04/22] i386/kvm: handle Xen HVM cpuid leaves David Woodhouse
2022-12-12 13:13 ` Paul Durrant
2022-12-13 9:47 ` David Woodhouse
2022-12-09 9:55 ` [RFC PATCH v2 05/22] xen-platform-pci: allow its creation with XEN_EMULATE mode David Woodhouse
2022-12-12 13:24 ` Paul Durrant
2022-12-12 22:07 ` David Woodhouse
2022-12-09 9:55 ` [RFC PATCH v2 06/22] hw/xen_backend: refactor xen_be_init() David Woodhouse
2022-12-12 13:27 ` Paul Durrant
2022-12-09 9:55 ` [RFC PATCH v2 07/22] pc_piix: handle XEN_EMULATE backend init David Woodhouse
2022-12-12 13:47 ` Paul Durrant
2022-12-12 14:50 ` David Woodhouse
2022-12-09 9:55 ` [RFC PATCH v2 08/22] xen_platform: exclude vfio-pci from the PCI platform unplug David Woodhouse
2022-12-12 13:52 ` Paul Durrant
2022-12-09 9:55 ` [RFC PATCH v2 09/22] pc_piix: allow xenfv machine with XEN_EMULATE David Woodhouse
2022-12-12 14:05 ` Paul Durrant
2022-12-09 9:56 ` [RFC PATCH v2 10/22] i386/xen: handle guest hypercalls David Woodhouse
2022-12-12 14:11 ` Paul Durrant
2022-12-12 14:17 ` David Woodhouse
2022-12-12 17:07 ` Paolo Bonzini
2022-12-09 9:56 ` [RFC PATCH v2 11/22] i386/xen: implement HYPERCALL_xen_version David Woodhouse
2022-12-12 14:17 ` Paul Durrant
2022-12-13 0:06 ` David Woodhouse
2022-12-09 9:56 ` [RFC PATCH v2 12/22] hw/xen: Add xen_overlay device for emulating shared xenheap pages David Woodhouse
2022-12-12 14:29 ` Paul Durrant
2022-12-12 17:14 ` Paolo Bonzini
2022-12-09 9:56 ` [RFC PATCH v2 13/22] i386/xen: implement HYPERVISOR_memory_op David Woodhouse
2022-12-12 14:38 ` Paul Durrant
2022-12-13 0:08 ` David Woodhouse
2022-12-09 9:56 ` [RFC PATCH v2 14/22] i386/xen: implement HYPERVISOR_hvm_op David Woodhouse
2022-12-12 14:41 ` Paul Durrant
2022-12-09 9:56 ` [RFC PATCH v2 15/22] i386/xen: implement HYPERVISOR_vcpu_op David Woodhouse
2022-12-12 14:51 ` Paul Durrant
2022-12-13 0:10 ` David Woodhouse
2022-12-09 9:56 ` [RFC PATCH v2 16/22] i386/xen: handle VCPUOP_register_vcpu_info David Woodhouse
2022-12-12 14:58 ` Paul Durrant
2022-12-13 0:13 ` David Woodhouse
2022-12-14 10:28 ` Paul Durrant
2022-12-14 11:04 ` David Woodhouse
2022-12-09 9:56 ` [RFC PATCH v2 17/22] i386/xen: handle VCPUOP_register_vcpu_time_info David Woodhouse
2022-12-12 15:34 ` Paul Durrant
2022-12-09 9:56 ` [RFC PATCH v2 18/22] i386/xen: handle VCPUOP_register_runstate_memory_area David Woodhouse
2022-12-12 15:38 ` Paul Durrant
2022-12-09 9:56 ` [RFC PATCH v2 19/22] i386/xen: implement HVMOP_set_evtchn_upcall_vector David Woodhouse
2022-12-12 15:52 ` Paul Durrant
2022-12-09 9:56 ` [RFC PATCH v2 20/22] i386/xen: HVMOP_set_param / HVM_PARAM_CALLBACK_IRQ David Woodhouse
2022-12-12 16:16 ` Paul Durrant
2022-12-12 16:26 ` David Woodhouse
2022-12-12 16:39 ` Paul Durrant
2022-12-15 20:54 ` David Woodhouse
2022-12-20 13:56 ` Paul Durrant
2022-12-20 16:27 ` David Woodhouse
2022-12-20 17:25 ` Paul Durrant [this message]
2022-12-20 17:29 ` David Woodhouse
2022-12-28 10:45 ` David Woodhouse
2022-12-21 1:41 ` David Woodhouse
2022-12-21 9:37 ` Paul Durrant
2022-12-21 12:16 ` David Woodhouse
2022-12-09 9:56 ` [RFC PATCH v2 21/22] i386/xen: implement HYPERVISOR_event_channel_op David Woodhouse
2022-12-12 16:23 ` Paul Durrant
2022-12-09 9:56 ` [RFC PATCH v2 22/22] i386/xen: implement HYPERVISOR_sched_op David Woodhouse
2022-12-12 16:37 ` Paul Durrant
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