Messages in this thread | | | Date | Fri, 14 Jan 2022 11:48:04 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH 1/5] kvm: add exit_to_guest_mode() and enter_from_guest_mode() |
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On Thu, Jan 13, 2022 at 08:32:20PM +0000, Sean Christopherson wrote: > On Tue, Jan 11, 2022, Mark Rutland wrote: > > Atop this, new exit_to_guest_mode() and enter_from_guest_mode() helpers > > are added to handle the ordering of lockdep, tracing, and RCU manageent. > > These are named to align with exit_to_user_mode() and > > enter_from_user_mode(). > > > > Subsequent patches will migrate architectures over to the new helpers, > > following a sequence: > > > > guest_timing_enter_irqoff(); > > > > exit_to_guest_mode(); > > I'm not a fan of this nomenclature. First and foremost, virtualization refers to > transfers to guest mode as VM-Enter, and transfers from guest mode as VM-Exit. > It's really, really confusing to read this code from a virtualization perspective. > The functions themselves are contradictory as the "enter" helper calls functions > with "exit" in their name, and vice versa.
Sure; FWIW I wasn't happy with the naming either, but I couldn't find anything that was entirely clear, because it depends on whether you consider this an entry..exit of guest context or an exit..entry of regular kernel context. I went with exit_to_guest_mode() and enter_from_guest_mode() because that clearly corresponded to exit_to_user_mode() and enter_from_user_mode(), and the convention in the common entry code is to talk in terms of the regular kernel context.
While I was working on this, I had guest_context_enter_irqoff() for kernel->guest and guest_context_exit_irqoff() for guest->kernel, which also matched the style of guest_timing_{enter,exit}_irqoff().
I'm happy to change to that, if that works for you?
> We settled on xfer_to_guest_mode_work() for a similar conundrum in the past, though > I don't love using xfer_to/from_guest_mode() as that makes it sound like those > helpers handle the actual transition into guest mode, i.e. runs the vCPU. > > To avoid too much bikeshedding, what about reusing the names we all compromised > on when we did this for x86 and call them kvm_guest_enter/exit_irqoff()? If x86 > is converted in the first patch then we could even avoid temporary #ifdefs.
I'd like to keep this somewhat orthogonal to the x86 changes (e.g. as other architectures will need backports to stable at least for the RCU bug fix), so I'd rather use a name that isn't immediately coupled with x86 changes.
Does the guest_context_{enter,exit}_irqoff() naming above work for you?
Thanks, Mark.
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