From: Julien Grall <julien.grall.oss@gmail.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Wei Liu <wl@xen.org>, Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Oleksandr Tyshchenko <olekstysh@gmail.com>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
Julien Grall <julien.grall@arm.com>,
Jan Beulich <jbeulich@suse.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [RFC PATCH V1 05/12] hvm/dm: Introduce xendevicemodel_set_irq_level DM op
Date: Sat, 8 Aug 2020 10:28:49 +0100 [thread overview]
Message-ID: <CAJ=z9a3UKeV90pJ_aPjZiOfpApA+vwFHcoEqLaAUiVMTSLqqCg@mail.gmail.com> (raw)
In-Reply-To: <CAJ=z9a3ngzDS6Fu5DwdRSzWaMASPgp3cZLnpazMQzUbH-9_EEw@mail.gmail.com>
On Sat, 8 Aug 2020 at 10:27, Julien Grall <julien.grall.oss@gmail.com> wrote:
>
> On Fri, 7 Aug 2020 at 22:51, Stefano Stabellini <sstabellini@kernel.org> wrote:
> >
> > On Fri, 7 Aug 2020, Jan Beulich wrote:
> > > On 07.08.2020 01:49, Stefano Stabellini wrote:
> > > > On Thu, 6 Aug 2020, Julien Grall wrote:
> > > >> On 06/08/2020 01:37, Stefano Stabellini wrote:
> > > >>> On Wed, 5 Aug 2020, Julien Grall wrote:
> > > >>>> On 05/08/2020 00:22, Stefano Stabellini wrote:
> > > >>>>> On Mon, 3 Aug 2020, Oleksandr Tyshchenko wrote:
> > > >>>>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> > > >>>>>>
> > > >>>>>> This patch adds ability to the device emulator to notify otherend
> > > >>>>>> (some entity running in the guest) using a SPI and implements Arm
> > > >>>>>> specific bits for it. Proposed interface allows emulator to set
> > > >>>>>> the logical level of a one of a domain's IRQ lines.
> > > >>>>>>
> > > >>>>>> Please note, this is a split/cleanup of Julien's PoC:
> > > >>>>>> "Add support for Guest IO forwarding to a device emulator"
> > > >>>>>>
> > > >>>>>> Signed-off-by: Julien Grall <julien.grall@arm.com>
> > > >>>>>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> > > >>>>>> ---
> > > >>>>>> tools/libs/devicemodel/core.c | 18
> > > >>>>>> ++++++++++++++++++
> > > >>>>>> tools/libs/devicemodel/include/xendevicemodel.h | 4 ++++
> > > >>>>>> tools/libs/devicemodel/libxendevicemodel.map | 1 +
> > > >>>>>> xen/arch/arm/dm.c | 22
> > > >>>>>> +++++++++++++++++++++-
> > > >>>>>> xen/common/hvm/dm.c | 1 +
> > > >>>>>> xen/include/public/hvm/dm_op.h | 15
> > > >>>>>> +++++++++++++++
> > > >>>>>> 6 files changed, 60 insertions(+), 1 deletion(-)
> > > >>>>>>
> > > >>>>>> diff --git a/tools/libs/devicemodel/core.c
> > > >>>>>> b/tools/libs/devicemodel/core.c
> > > >>>>>> index 4d40639..30bd79f 100644
> > > >>>>>> --- a/tools/libs/devicemodel/core.c
> > > >>>>>> +++ b/tools/libs/devicemodel/core.c
> > > >>>>>> @@ -430,6 +430,24 @@ int xendevicemodel_set_isa_irq_level(
> > > >>>>>> return xendevicemodel_op(dmod, domid, 1, &op, sizeof(op));
> > > >>>>>> }
> > > >>>>>> +int xendevicemodel_set_irq_level(
> > > >>>>>> + xendevicemodel_handle *dmod, domid_t domid, uint32_t irq,
> > > >>>>>> + unsigned int level)
> > > >>>>>
> > > >>>>> It is a pity that having xen_dm_op_set_pci_intx_level and
> > > >>>>> xen_dm_op_set_isa_irq_level already we need to add a third one, but from
> > > >>>>> the names alone I don't think we can reuse either of them.
> > > >>>>
> > > >>>> The problem is not the name...
> > > >>>>
> > > >>>>>
> > > >>>>> It is very similar to set_isa_irq_level. We could almost rename
> > > >>>>> xendevicemodel_set_isa_irq_level to xendevicemodel_set_irq_level or,
> > > >>>>> better, just add an alias to it so that xendevicemodel_set_irq_level is
> > > >>>>> implemented by calling xendevicemodel_set_isa_irq_level. Honestly I am
> > > >>>>> not sure if it is worth doing it though. Any other opinions?
> > > >>>>
> > > >>>> ... the problem is the interrupt field is only 8-bit. So we would only be
> > > >>>> able
> > > >>>> to cover IRQ 0 - 255.
> > > >>>
> > > >>> Argh, that's not going to work :-( I wasn't sure if it was a good idea
> > > >>> anyway.
> > > >>>
> > > >>>
> > > >>>> It is not entirely clear how the existing subop could be extended without
> > > >>>> breaking existing callers.
> > > >>>>
> > > >>>>> But I think we should plan for not needing two calls (one to set level
> > > >>>>> to 1, and one to set it to 0):
> > > >>>>> https://marc.info/?l=xen-devel&m=159535112027405
> > > >>>>
> > > >>>> I am not sure to understand your suggestion here? Are you suggesting to
> > > >>>> remove
> > > >>>> the 'level' parameter?
> > > >>>
> > > >>> My hope was to make it optional to call the hypercall with level = 0,
> > > >>> not necessarily to remove 'level' from the struct.
> > > >>
> > > >> From my understanding, the hypercall is meant to represent the status of the
> > > >> line between the device and the interrupt controller (either low or high).
> > > >>
> > > >> This is then up to the interrupt controller to decide when the interrupt is
> > > >> going to be fired:
> > > >> - For edge interrupt, this will fire when the line move from low to high (or
> > > >> vice versa).
> > > >> - For level interrupt, this will fire when line is high (assuming level
> > > >> trigger high) and will keeping firing until the device decided to lower the
> > > >> line.
> > > >>
> > > >> For a device, it is common to keep the line high until an OS wrote to a
> > > >> specific register.
> > > >>
> > > >> Furthermore, technically, the guest OS is in charge to configure how an
> > > >> interrupt is triggered. Admittely this information is part of the DT, but
> > > >> nothing prevent a guest to change it.
> > > >>
> > > >> As side note, we have a workaround in Xen for some buggy DT (see the arch
> > > >> timer) exposing the wrong trigger type.
> > > >>
> > > >> Because of that, I don't really see a way to make optional. Maybe you have
> > > >> something different in mind?
> > > >
> > > > For level, we need the level parameter. For edge, we are only interested
> > > > in the "edge", right?
> > >
> > > I don't think so, unless Arm has special restrictions. Edges can be
> > > both rising and falling ones.
> >
> > And the same is true for level interrupts too: they could be active-low
> > or active-high.
> >
> >
> > Instead of modelling the state of the line, which seems to be a bit
> > error prone especially in the case of a single-device emulator that
> > might not have enough information about the rest of the system (it might
> > not know if the interrupt is active-high or active-low), we could model
> > the triggering of the interrupt instead.
>
> I am not sure to understand why the single (or event multiple) device
> emulator needs to know the trigger type. The information of the
I mean trigger type configured by the OS here. Sorry for the confusion.
> trigger type of the interrupt would be described in the firmware table
> and it is expected to be the same as what the emulator expects.
>
> If the guest OS decided to configure wrongly the interrupt trigger
> type, then it may not work properly. But, from my understanding, this
> doesn't differ from the HW behavior.
>
> >
> > In the case of level=1, it would mean that the interrupt line is active,
> > no matter if it is active-low or active-high. In the case of level=0, it
> > would mean that it is inactive.
> >
> > Similarly, in the case of an edge interrupt edge=1 or level=1 would mean
> > that there is an edge, no matter if it is rising or falling.
>
> TBH, I think your approach is only going to introduce more headache in
> Xen if a guest OS decides to change the trigger type.
>
> It feels much easier to just ask the emulator to let us know the level
> of the line. Then if the guest OS decides to change the trigger type,
> we only need to resample the line.
>
> Cheers,
next prev parent reply other threads:[~2020-08-08 9:29 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 18:21 [RFC PATCH V1 00/12] IOREQ feature (+ virtio-mmio) on Arm Oleksandr Tyshchenko
2020-08-03 18:21 ` [RFC PATCH V1 01/12] hvm/ioreq: Make x86's IOREQ feature common Oleksandr Tyshchenko
2020-08-04 7:45 ` Paul Durrant
2020-08-04 11:10 ` Oleksandr
2020-08-04 11:23 ` Paul Durrant
2020-08-04 11:51 ` Oleksandr
2020-08-04 13:18 ` Paul Durrant
2020-08-04 13:52 ` Julien Grall
2020-08-04 15:41 ` Jan Beulich
2020-08-04 19:11 ` Stefano Stabellini
2020-08-05 7:01 ` Jan Beulich
2020-08-06 0:37 ` Stefano Stabellini
2020-08-06 6:59 ` Jan Beulich
2020-08-06 20:32 ` Stefano Stabellini
2020-08-07 13:19 ` Oleksandr
2020-08-07 16:45 ` Oleksandr
2020-08-07 21:50 ` Stefano Stabellini
2020-08-07 22:19 ` Oleksandr
2020-08-10 13:41 ` Oleksandr
2020-08-10 23:34 ` Stefano Stabellini
2020-08-11 9:19 ` Julien Grall
2020-08-11 10:10 ` Oleksandr
2020-08-11 22:47 ` Stefano Stabellini
2020-08-12 14:35 ` Oleksandr
2020-08-12 23:08 ` Stefano Stabellini
2020-08-13 20:16 ` Julien Grall
2020-08-07 23:45 ` Oleksandr
2020-08-10 23:34 ` Stefano Stabellini
2020-08-05 8:33 ` Julien Grall
2020-08-06 0:37 ` Stefano Stabellini
2020-08-06 9:45 ` Julien Grall
2020-08-06 23:48 ` Stefano Stabellini
2020-08-10 19:20 ` Julien Grall
2020-08-10 23:34 ` Stefano Stabellini
2020-08-11 11:28 ` Julien Grall
2020-08-11 22:48 ` Stefano Stabellini
2020-08-12 8:19 ` Julien Grall
2020-08-20 19:14 ` Oleksandr
2020-08-21 0:53 ` Stefano Stabellini
2020-08-21 18:54 ` Julien Grall
2020-08-05 13:30 ` Julien Grall
2020-08-06 11:37 ` Oleksandr
2020-08-10 16:29 ` Julien Grall
2020-08-10 17:28 ` Oleksandr
2020-08-05 16:15 ` Andrew Cooper
2020-08-06 8:20 ` Oleksandr
2020-08-15 17:30 ` Julien Grall
2020-08-16 19:37 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 02/12] hvm/dm: Make x86's DM " Oleksandr Tyshchenko
2020-08-03 18:21 ` [RFC PATCH V1 03/12] xen/mm: Make x86's XENMEM_resource_ioreq_server handling common Oleksandr Tyshchenko
2020-08-03 18:21 ` [RFC PATCH V1 04/12] xen/arm: Introduce arch specific bits for IOREQ/DM features Oleksandr Tyshchenko
2020-08-04 7:49 ` Paul Durrant
2020-08-04 14:01 ` Julien Grall
2020-08-04 23:22 ` Stefano Stabellini
2020-08-15 17:56 ` Julien Grall
2020-08-17 14:36 ` Oleksandr
2020-08-04 23:22 ` Stefano Stabellini
2020-08-05 7:05 ` Jan Beulich
2020-08-05 16:41 ` Stefano Stabellini
2020-08-05 19:45 ` Oleksandr
2020-08-05 9:32 ` Julien Grall
2020-08-05 15:41 ` Oleksandr
2020-08-06 10:19 ` Julien Grall
2020-08-10 18:09 ` Oleksandr
2020-08-10 18:21 ` Oleksandr
2020-08-10 19:00 ` Julien Grall
2020-08-10 20:29 ` Oleksandr
2020-08-10 22:37 ` Julien Grall
2020-08-11 6:13 ` Oleksandr
2020-08-12 15:08 ` Oleksandr
2020-08-11 17:09 ` Oleksandr
2020-08-11 17:50 ` Julien Grall
2020-08-13 18:41 ` Oleksandr
2020-08-13 20:36 ` Julien Grall
2020-08-13 21:49 ` Oleksandr
2020-08-13 20:39 ` Oleksandr Tyshchenko
2020-08-13 22:14 ` Julien Grall
2020-08-14 12:08 ` Oleksandr
2020-08-05 14:12 ` Julien Grall
2020-08-05 14:45 ` Jan Beulich
2020-08-05 19:30 ` Oleksandr
2020-08-06 11:08 ` Julien Grall
2020-08-06 11:29 ` Jan Beulich
2020-08-20 18:30 ` Oleksandr
2020-08-21 6:16 ` Jan Beulich
2020-08-21 11:13 ` Oleksandr
2020-08-06 13:27 ` Oleksandr
2020-08-10 18:25 ` Julien Grall
2020-08-10 19:58 ` Oleksandr
2020-08-05 16:13 ` Jan Beulich
2020-08-05 19:47 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 05/12] hvm/dm: Introduce xendevicemodel_set_irq_level DM op Oleksandr Tyshchenko
2020-08-04 23:22 ` Stefano Stabellini
2020-08-05 9:39 ` Julien Grall
2020-08-06 0:37 ` Stefano Stabellini
2020-08-06 11:32 ` Julien Grall
2020-08-06 23:49 ` Stefano Stabellini
2020-08-07 8:43 ` Jan Beulich
2020-08-07 21:50 ` Stefano Stabellini
2020-08-08 9:27 ` Julien Grall
2020-08-08 9:28 ` Julien Grall [this message]
2020-08-10 23:34 ` Stefano Stabellini
2020-08-11 13:04 ` Julien Grall
2020-08-11 22:48 ` Stefano Stabellini
2020-08-18 9:31 ` Julien Grall
2020-08-21 0:53 ` Stefano Stabellini
2020-08-17 15:23 ` Jan Beulich
2020-08-17 22:56 ` Stefano Stabellini
2020-08-18 8:03 ` Jan Beulich
2020-08-05 16:15 ` Jan Beulich
2020-08-05 22:12 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 06/12] libxl: Introduce basic virtio-mmio support on Arm Oleksandr Tyshchenko
2020-08-03 18:21 ` [RFC PATCH V1 07/12] A collection of tweaks to be able to run emulator in driver domain Oleksandr Tyshchenko
2020-08-05 16:19 ` Jan Beulich
2020-08-05 16:40 ` Paul Durrant
2020-08-06 9:22 ` Oleksandr
2020-08-06 9:27 ` Jan Beulich
2020-08-14 16:30 ` Oleksandr
2020-08-16 15:36 ` Julien Grall
2020-08-17 15:07 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 08/12] xen/arm: Invalidate qemu mapcache on XENMEM_decrease_reservation Oleksandr Tyshchenko
2020-08-05 16:21 ` Jan Beulich
2020-08-06 11:35 ` Julien Grall
2020-08-06 11:50 ` Jan Beulich
2020-08-06 14:28 ` Oleksandr
2020-08-06 16:33 ` Jan Beulich
2020-08-06 16:57 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 09/12] libxl: Handle virtio-mmio irq in more correct way Oleksandr Tyshchenko
2020-08-04 23:22 ` Stefano Stabellini
2020-08-05 20:51 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 10/12] libxl: Add support for virtio-disk configuration Oleksandr Tyshchenko
2020-08-04 23:23 ` Stefano Stabellini
2020-08-05 21:12 ` Oleksandr
2020-08-06 0:37 ` Stefano Stabellini
2020-08-03 18:21 ` [RFC PATCH V1 11/12] libxl: Insert "dma-coherent" property into virtio-mmio device node Oleksandr Tyshchenko
2020-08-04 23:23 ` Stefano Stabellini
2020-08-05 20:35 ` Oleksandr
2020-08-03 18:21 ` [RFC PATCH V1 12/12] libxl: Fix duplicate memory node in DT Oleksandr Tyshchenko
2020-08-15 17:24 ` [RFC PATCH V1 00/12] IOREQ feature (+ virtio-mmio) on Arm Julien Grall
2020-08-16 19:34 ` Oleksandr
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