From: Mark Rutland <mark.rutland@arm.com>
To: Sean Christopherson <seanjc@google.com>
Cc: linux-kernel@vger.kernel.org, aleksandar.qemu.devel@gmail.com,
alexandru.elisei@arm.com, anup.patel@wdc.com,
aou@eecs.berkeley.edu, atish.patra@wdc.com,
benh@kernel.crashing.org, borntraeger@linux.ibm.com,
bp@alien8.de, catalin.marinas@arm.com, chenhuacai@kernel.org,
dave.hansen@linux.intel.com, david@redhat.com,
frankja@linux.ibm.com, frederic@kernel.org, gor@linux.ibm.com,
hca@linux.ibm.com, imbrenda@linux.ibm.com, james.morse@arm.com,
jmattson@google.com, joro@8bytes.org, kvm@vger.kernel.org,
maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au,
nsaenzju@redhat.com, palmer@dabbelt.com, paulmck@kernel.org,
paulus@samba.org, paul.walmsley@sifive.com, pbonzini@redhat.com,
suzuki.poulose@arm.com, tglx@linutronix.de,
tsbogend@alpha.franken.de, vkuznets@redhat.com,
wanpengli@tencent.com, will@kernel.org
Subject: Re: [PATCH 1/5] kvm: add exit_to_guest_mode() and enter_from_guest_mode()
Date: Fri, 14 Jan 2022 11:48:04 +0000 [thread overview]
Message-ID: <YeFi9FTPSyLbQytu@FVFF77S0Q05N> (raw)
In-Reply-To: <YeCMVGqiVfTKESzy@google.com>
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.
next prev parent reply other threads:[~2022-01-14 11:48 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-11 15:35 [PATCH 0/5] kvm: fix latent guest entry/exit bugs Mark Rutland
2022-01-11 15:35 ` [PATCH 1/5] kvm: add exit_to_guest_mode() and enter_from_guest_mode() Mark Rutland
2022-01-11 17:54 ` Marc Zyngier
2022-01-13 11:01 ` Mark Rutland
2022-01-13 11:55 ` Marc Zyngier
2022-01-13 13:01 ` Mark Rutland
2022-01-13 20:32 ` Sean Christopherson
2022-01-14 11:48 ` Mark Rutland [this message]
2022-01-14 16:11 ` Sean Christopherson
2022-01-18 13:01 ` Mark Rutland
2022-01-11 15:35 ` [PATCH 2/5] kvm/arm64: rework guest entry logic Mark Rutland
2022-01-11 17:55 ` Marc Zyngier
2022-01-13 11:17 ` Mark Rutland
2022-01-13 11:43 ` Marc Zyngier
2022-01-13 12:58 ` Mark Rutland
2022-01-11 15:35 ` [PATCH 3/5] kvm/mips: " Mark Rutland
2022-01-11 15:35 ` [PATCH 4/5] kvm/riscv: " Mark Rutland
2022-01-11 15:35 ` [PATCH 5/5] kvm/x86: " Mark Rutland
2022-01-13 20:50 ` Sean Christopherson
2022-01-14 12:05 ` Mark Rutland
2022-01-14 16:49 ` Sean Christopherson
2022-01-11 18:47 ` [PATCH 0/5] kvm: fix latent guest entry/exit bugs Palmer Dabbelt
2022-01-13 15:20 ` Christian Borntraeger
2022-01-14 12:19 ` Mark Rutland
2022-01-14 12:29 ` Christian Borntraeger
2022-01-14 13:32 ` Mark Rutland
2022-01-14 13:51 ` Christian Borntraeger
2022-01-14 15:19 ` Mark Rutland
2022-01-17 17:45 ` Paolo Bonzini
2022-01-18 12:02 ` Mark Rutland
2022-01-18 12:08 ` Christian Borntraeger
2022-01-18 12:42 ` Christian Borntraeger
2022-01-18 13:12 ` Mark Rutland
2022-01-18 14:15 ` Christian Borntraeger
2022-01-18 15:43 ` Mark Rutland
2022-01-18 16:09 ` Sven Schnelle
2022-01-18 17:50 ` Mark Rutland
2022-01-18 18:12 ` Mark Rutland
2022-01-19 6:41 ` Sven Schnelle
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