On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote:
> On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote:
> > This driver creates per-cpu hrtimers which are required to do the
> > periodic 'pet' operation. On a conventional watchdog-core driver, the
> > userspace is responsible for delivering the 'pet' events by writing to
> > the particular /dev/watchdogN node. In this case we require a strong
> > thread affinity to be able to account for lost time on a per vCPU.
> >
> > This part of the driver is the 'frontend' which is reponsible for
> > delivering the periodic 'pet' events, configuring the virtual peripheral
> > and listening for cpu hotplug events. The other part of the driver
> > handles the peripheral emulation and this part accounts for lost time by
> > looking at the /proc/{}/task/{}/stat entries and is located here:
> > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
> >
> > Signed-off-by: Sebastian Ene <[email protected]>
> > ---
> > drivers/misc/Kconfig | 12 +++
> > drivers/misc/Makefile | 1 +
> > drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++
> > 3 files changed, 219 insertions(+)
> > create mode 100644 drivers/misc/vm-watchdog.c
> >
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 2b9572a6d114..26c3a99e269c 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -493,6 +493,18 @@ config OPEN_DICE
> >
> > If unsure, say N.
> >
> > +config VM_WATCHDOG
> > + tristate "Virtual Machine Watchdog"
> > + select LOCKUP_DETECTOR
> > + help
> > + Detect CPU locks on the virtual machine. This driver relies on the
> > + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU
> > + has to do a 'pet', it exits the guest through MMIO write and the
> > + backend driver takes into account the lost ticks for this particular
> > + CPU.
Hi,
>
> There's nothing to keep this tied to a virtual machine at all, right?
> You are just relying on some iomem address to be updated, so it should
> be a "generic_iomem_watchdog" driver as there's nothing specific to vms
> at all from what I can tell.
>
> thanks,
>
> greg k-h
That's right although I might think of using the term "generic lockup detector"
instead of watchdog. The only reason why I would keep "virtual machine"
word in, is that there is no actual hardware for this.
Thanks,
Seb
On Fri, Apr 29, 2022 at 09:26:26AM +0000, Sebastian Ene wrote:
> On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote:
> > On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote:
> > > This driver creates per-cpu hrtimers which are required to do the
> > > periodic 'pet' operation. On a conventional watchdog-core driver, the
> > > userspace is responsible for delivering the 'pet' events by writing to
> > > the particular /dev/watchdogN node. In this case we require a strong
> > > thread affinity to be able to account for lost time on a per vCPU.
> > >
> > > This part of the driver is the 'frontend' which is reponsible for
> > > delivering the periodic 'pet' events, configuring the virtual peripheral
> > > and listening for cpu hotplug events. The other part of the driver
> > > handles the peripheral emulation and this part accounts for lost time by
> > > looking at the /proc/{}/task/{}/stat entries and is located here:
> > > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
> > >
> > > Signed-off-by: Sebastian Ene <[email protected]>
> > > ---
> > > drivers/misc/Kconfig | 12 +++
> > > drivers/misc/Makefile | 1 +
> > > drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++
> > > 3 files changed, 219 insertions(+)
> > > create mode 100644 drivers/misc/vm-watchdog.c
> > >
> > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > > index 2b9572a6d114..26c3a99e269c 100644
> > > --- a/drivers/misc/Kconfig
> > > +++ b/drivers/misc/Kconfig
> > > @@ -493,6 +493,18 @@ config OPEN_DICE
> > >
> > > If unsure, say N.
> > >
> > > +config VM_WATCHDOG
> > > + tristate "Virtual Machine Watchdog"
> > > + select LOCKUP_DETECTOR
> > > + help
> > > + Detect CPU locks on the virtual machine. This driver relies on the
> > > + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU
> > > + has to do a 'pet', it exits the guest through MMIO write and the
> > > + backend driver takes into account the lost ticks for this particular
> > > + CPU.
>
> Hi,
>
> >
> > There's nothing to keep this tied to a virtual machine at all, right?
> > You are just relying on some iomem address to be updated, so it should
> > be a "generic_iomem_watchdog" driver as there's nothing specific to vms
> > at all from what I can tell.
> >
> > thanks,
> >
> > greg k-h
>
> That's right although I might think of using the term "generic lockup detector"
> instead of watchdog. The only reason why I would keep "virtual machine"
> word in, is that there is no actual hardware for this.
That doesn't really matter, it's just a memory location in device tree
that you are needing, odds are some hardware device could use it just
like this.
thanks,
greg k-h
On 4/29/22 02:26, Sebastian Ene wrote:
> On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote:
>> On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote:
>>> This driver creates per-cpu hrtimers which are required to do the
>>> periodic 'pet' operation. On a conventional watchdog-core driver, the
>>> userspace is responsible for delivering the 'pet' events by writing to
>>> the particular /dev/watchdogN node. In this case we require a strong
>>> thread affinity to be able to account for lost time on a per vCPU.
>>>
>>> This part of the driver is the 'frontend' which is reponsible for
>>> delivering the periodic 'pet' events, configuring the virtual peripheral
>>> and listening for cpu hotplug events. The other part of the driver
>>> handles the peripheral emulation and this part accounts for lost time by
>>> looking at the /proc/{}/task/{}/stat entries and is located here:
>>> https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
>>>
>>> Signed-off-by: Sebastian Ene <[email protected]>
>>> ---
>>> drivers/misc/Kconfig | 12 +++
>>> drivers/misc/Makefile | 1 +
>>> drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 219 insertions(+)
>>> create mode 100644 drivers/misc/vm-watchdog.c
>>>
>>> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
>>> index 2b9572a6d114..26c3a99e269c 100644
>>> --- a/drivers/misc/Kconfig
>>> +++ b/drivers/misc/Kconfig
>>> @@ -493,6 +493,18 @@ config OPEN_DICE
>>>
>>> If unsure, say N.
>>>
>>> +config VM_WATCHDOG
>>> + tristate "Virtual Machine Watchdog"
>>> + select LOCKUP_DETECTOR
>>> + help
>>> + Detect CPU locks on the virtual machine. This driver relies on the
>>> + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU
>>> + has to do a 'pet', it exits the guest through MMIO write and the
>>> + backend driver takes into account the lost ticks for this particular
>>> + CPU.
>
> Hi,
>
>>
>> There's nothing to keep this tied to a virtual machine at all, right?
>> You are just relying on some iomem address to be updated, so it should
>> be a "generic_iomem_watchdog" driver as there's nothing specific to vms
>> at all from what I can tell.
>>
>> thanks,
>>
>> greg k-h
>
> That's right although I might think of using the term "generic lockup detector"
Agreed, that would be a much better name.
Guenter
> instead of watchdog. The only reason why I would keep "virtual machine"
> word in, is that there is no actual hardware for this.
>
> Thanks,
> Seb
On Fri, Apr 29, 2022 at 11:38:52AM +0200, Greg Kroah-Hartman wrote:
> On Fri, Apr 29, 2022 at 09:26:26AM +0000, Sebastian Ene wrote:
> > On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote:
> > > On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote:
> > > > This driver creates per-cpu hrtimers which are required to do the
> > > > periodic 'pet' operation. On a conventional watchdog-core driver, the
> > > > userspace is responsible for delivering the 'pet' events by writing to
> > > > the particular /dev/watchdogN node. In this case we require a strong
> > > > thread affinity to be able to account for lost time on a per vCPU.
> > > >
> > > > This part of the driver is the 'frontend' which is reponsible for
> > > > delivering the periodic 'pet' events, configuring the virtual peripheral
> > > > and listening for cpu hotplug events. The other part of the driver
> > > > handles the peripheral emulation and this part accounts for lost time by
> > > > looking at the /proc/{}/task/{}/stat entries and is located here:
> > > > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
> > > >
> > > > Signed-off-by: Sebastian Ene <[email protected]>
> > > > ---
> > > > drivers/misc/Kconfig | 12 +++
> > > > drivers/misc/Makefile | 1 +
> > > > drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++
> > > > 3 files changed, 219 insertions(+)
> > > > create mode 100644 drivers/misc/vm-watchdog.c
> > > >
> > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > > > index 2b9572a6d114..26c3a99e269c 100644
> > > > --- a/drivers/misc/Kconfig
> > > > +++ b/drivers/misc/Kconfig
> > > > @@ -493,6 +493,18 @@ config OPEN_DICE
> > > >
> > > > If unsure, say N.
> > > >
> > > > +config VM_WATCHDOG
> > > > + tristate "Virtual Machine Watchdog"
> > > > + select LOCKUP_DETECTOR
> > > > + help
> > > > + Detect CPU locks on the virtual machine. This driver relies on the
> > > > + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU
> > > > + has to do a 'pet', it exits the guest through MMIO write and the
> > > > + backend driver takes into account the lost ticks for this particular
> > > > + CPU.
> >
> > Hi,
> >
> > >
> > > There's nothing to keep this tied to a virtual machine at all, right?
> > > You are just relying on some iomem address to be updated, so it should
> > > be a "generic_iomem_watchdog" driver as there's nothing specific to vms
> > > at all from what I can tell.
> > >
> > > thanks,
> > >
> > > greg k-h
> >
> > That's right although I might think of using the term "generic lockup detector"
> > instead of watchdog. The only reason why I would keep "virtual machine"
> > word in, is that there is no actual hardware for this.
>
> That doesn't really matter, it's just a memory location in device tree
> that you are needing, odds are some hardware device could use it just
> like this.
Such as a shared on-chip memory that both a system control processor and
the main processors can access. Of course, those also typically already
have a comnunication channel.
But for a VM-hypervisor interface, why isn't one of the existing
communications interfaces being used? One that is discoverable would be
better than using DT.
Rob
On Fri, Apr 29, 2022 at 04:03:45PM -0500, Rob Herring wrote:
> On Fri, Apr 29, 2022 at 11:38:52AM +0200, Greg Kroah-Hartman wrote:
> > On Fri, Apr 29, 2022 at 09:26:26AM +0000, Sebastian Ene wrote:
> > > On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote:
> > > > On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote:
> > > > > This driver creates per-cpu hrtimers which are required to do the
> > > > > periodic 'pet' operation. On a conventional watchdog-core driver, the
> > > > > userspace is responsible for delivering the 'pet' events by writing to
> > > > > the particular /dev/watchdogN node. In this case we require a strong
> > > > > thread affinity to be able to account for lost time on a per vCPU.
> > > > >
> > > > > This part of the driver is the 'frontend' which is reponsible for
> > > > > delivering the periodic 'pet' events, configuring the virtual peripheral
> > > > > and listening for cpu hotplug events. The other part of the driver
> > > > > handles the peripheral emulation and this part accounts for lost time by
> > > > > looking at the /proc/{}/task/{}/stat entries and is located here:
> > > > > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
> > > > >
> > > > > Signed-off-by: Sebastian Ene <[email protected]>
> > > > > ---
> > > > > drivers/misc/Kconfig | 12 +++
> > > > > drivers/misc/Makefile | 1 +
> > > > > drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++
> > > > > 3 files changed, 219 insertions(+)
> > > > > create mode 100644 drivers/misc/vm-watchdog.c
> > > > >
> > > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > > > > index 2b9572a6d114..26c3a99e269c 100644
> > > > > --- a/drivers/misc/Kconfig
> > > > > +++ b/drivers/misc/Kconfig
> > > > > @@ -493,6 +493,18 @@ config OPEN_DICE
> > > > >
> > > > > If unsure, say N.
> > > > >
> > > > > +config VM_WATCHDOG
> > > > > + tristate "Virtual Machine Watchdog"
> > > > > + select LOCKUP_DETECTOR
> > > > > + help
> > > > > + Detect CPU locks on the virtual machine. This driver relies on the
> > > > > + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU
> > > > > + has to do a 'pet', it exits the guest through MMIO write and the
> > > > > + backend driver takes into account the lost ticks for this particular
> > > > > + CPU.
> > >
> > > Hi,
> > >
> > > >
> > > > There's nothing to keep this tied to a virtual machine at all, right?
> > > > You are just relying on some iomem address to be updated, so it should
> > > > be a "generic_iomem_watchdog" driver as there's nothing specific to vms
> > > > at all from what I can tell.
> > > >
> > > > thanks,
> > > >
> > > > greg k-h
> > >
> > > That's right although I might think of using the term "generic lockup detector"
> > > instead of watchdog. The only reason why I would keep "virtual machine"
> > > word in, is that there is no actual hardware for this.
> >
> > That doesn't really matter, it's just a memory location in device tree
> > that you are needing, odds are some hardware device could use it just
> > like this.
Hi,
>
> Such as a shared on-chip memory that both a system control processor and
> the main processors can access. Of course, those also typically already
> have a comnunication channel.
>
> But for a VM-hypervisor interface, why isn't one of the existing
> communications interfaces being used? One that is discoverable would be
> better than using DT.
>
In a protected VM we don't trust the host to present and control the loaded
peripherals. We rely on another entity to generate a trusted device tree
for us. I hope this clarifies the need for DT and I think this information
should also be added in the changelog.
> Rob
Thanks,
Seb