linux-kernel - Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED

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Message-ID: <3188ca61-2591-4576-9777-1671689b7235@linux.microsoft.com>
Date: Mon, 25 Aug 2025 16:08:45 -0700
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Sean Christopherson <seanjc@...gle.com>, Marc Zyngier <maz@...nel.org>,
 Oliver Upton <oliver.upton@...ux.dev>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>, Anup Patel <anup@...infault.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>, Peter Zijlstra <peterz@...radead.org>,
 Andy Lutomirski <luto@...nel.org>, "Paul E. McKenney" <paulmck@...nel.org>,
 Frederic Weisbecker <frederic@...nel.org>,
 Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
 Joel Fernandes <joelagnelf@...dia.com>, Josh Triplett
 <josh@...htriplett.org>, Boqun Feng <boqun.feng@...il.com>,
 Uladzislau Rezki <urezki@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 kvmarm@...ts.linux.dev, kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
 linux-hyperv@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common
 APIs

On 8/25/2025 1:06 PM, Sean Christopherson wrote:
> Fix a bug where MSHV root partitions don't honor NEED_RESCHED_LAZY, and then
> deduplicate the TIF related MSHV code by turning the "kvm" entry APIs into
> more generic "virt" APIs (which ideally would have been done when MSHV root
> support was added).
> 
> Assuming all is well, maybe this could go through the tip tree?
> 
> The Hyper-V stuff and non-x86 architectures are compile-tested only.
> 

Thanks Sean, I can test the root partition changes.

A similar change will be needed in mshv_vtl_main.c since it also calls
mshv_do_pre_guest_mode_work() (hence the "common" in mshv_common.c).

Also, is it possible to make all the mshv driver changes in a single patch?
It seems like it would be cleaner than refactoring it in patches 1 & 2 and
then deleting all the refactored code in patch 5.

Thanks
Nuno

> Sean Christopherson (5):
>   Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c
>   Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
>   entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM
>     proper
>   entry: Rename "kvm" entry code assets to "virt" to genericize APIs
>   Drivers: hv: Use common "entry virt" APIs to do work before running
>     guest
> 
>  MAINTAINERS                                 |  2 +-
>  arch/arm64/kvm/Kconfig                      |  2 +-
>  arch/arm64/kvm/arm.c                        |  3 +-
>  arch/loongarch/kvm/Kconfig                  |  2 +-
>  arch/loongarch/kvm/vcpu.c                   |  3 +-
>  arch/riscv/kvm/Kconfig                      |  2 +-
>  arch/riscv/kvm/vcpu.c                       |  3 +-
>  arch/x86/kvm/Kconfig                        |  2 +-
>  arch/x86/kvm/vmx/vmx.c                      |  1 -
>  arch/x86/kvm/x86.c                          |  3 +-
>  drivers/hv/Kconfig                          |  1 +
>  drivers/hv/mshv.h                           |  2 --
>  drivers/hv/mshv_common.c                    | 22 ---------------
>  drivers/hv/mshv_root_main.c                 | 31 ++++-----------------
>  include/linux/{entry-kvm.h => entry-virt.h} | 19 +++++--------
>  include/linux/kvm_host.h                    | 17 +++++++++--
>  include/linux/rcupdate.h                    |  2 +-
>  kernel/entry/Makefile                       |  2 +-
>  kernel/entry/{kvm.c => virt.c}              | 15 ++++------
>  kernel/rcu/tree.c                           |  6 ++--
>  virt/kvm/Kconfig                            |  2 +-
>  21 files changed, 49 insertions(+), 93 deletions(-)
>  rename include/linux/{entry-kvm.h => entry-virt.h} (83%)
>  rename kernel/entry/{kvm.c => virt.c} (66%)
> 
> 
> base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00