Messages in this thread | | | Date | Thu, 3 Nov 2022 15:10:07 -0700 | Subject | Re: [PATCH v6 13/21] gunyah: vm_mgr: Introduce basic VM Manager | From | Elliot Berman <> |
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On 11/3/2022 2:39 AM, Arnd Bergmann wrote: > On Wed, Nov 2, 2022, at 19:44, Elliot Berman wrote: >> On 11/2/2022 12:31 AM, Arnd Bergmann wrote: >>>> +static long gh_dev_ioctl_create_vm(unsigned long arg) >>>> +{ >>>> + struct gunyah_vm *ghvm; >>>> + struct file *file; >>>> + int fd, err; >>>> + >>>> + /* arg reserved for future use. */ >>>> + if (arg) >>>> + return -EINVAL; >>> >>> Do you have something specific in mind here? If 'create' >>> is the only command you support, and it has no arguments, >>> it would be easier to do it implicitly during open() and >>> have each fd opened from /dev/gunyah represent a new VM. >>> >> >> I'd like the argument here to support different types of virtual >> machines. I want to leave open what "different types" can be in case >> something new comes up in the future, but immediately "different type" >> would correspond to a few different authentication mechanisms for >> virtual machines that Gunyah supports. >> >> In this series, I'm only supporting unauthenticated virtual machines >> because they are the simplest to get up and running from a Linux >> userspace. When I introduce the other authentication mechanisms, I'll >> expand much more on how they work, but I'll give quick overview here. >> Other authentication mechanisms that are currently supported by Gunyah >> are "protected VM" and, on Qualcomm platforms, "PIL/carveout VMs". >> Protected VMs are *loosely* similar to the protected firmware design for >> KVM and intended to support Android virtualization use cases. >> PIL/carevout VMs are special virtual machines that can run on Qualcomm >> firmware which authenticate in a way similar to remoteproc firmware (MDT >> loader). > > Ok, thanks for the background. Having different types of virtual > machines does mean that you may need some complexity, but I would > still lean towards using the simpler context management of opening > the /dev/gunyah device node to get a new context, and then using > ioctls on each fd to manage that context, instead of going through > the extra indirection of having a secondary 'open context' command > that always requires opening two file descriptors. > >>> I'm correct, you can just turn the entire bus/device/driver >>> structure within your code into simple function calls, where >>> the main code calls vm_mgr_probe() as an exported function >>> instead of creating a device. >> >> Ack. I can do this, although I am nervous about this snowballing into a >> situation where I have a mega-module. >> >> > Please stop beating everything in a single module. >> >> https://lore.kernel.org/all/250945d2-3940-9830-63e5-beec5f44010b@linaro.org/ > > I see you concern, but I wasn't suggesting having everything > in one module either. There are three common ways of splitting > things into separate modules: > > - I suggested having the vm_mgr module as a library block that > exports a few symbols which get used by the core module. The > module doesn't do anything on its own, but loading the core > module forces loading the vm_mgr. >
Got the idea, I'll do this.
- Elliot
> - Alternatively one can do the opposite, and have symbols > exported by the core module, with the vm_mgr module using > it. This would make sense if you commonly have the core > module loaded on virtual machines that do not need to manage > other VMs. > > - The method you have is to have a lower "bus" level that > abstracts device providers from consumers, with both sides > hooking into the bus. This makes sense for physical buses > like PCI or USB where both the host driver and the function > driver are unaware of implementation details of the other, > but in your case it does not seem like a good fit. > > Arnd
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