linux-kernel - Re: [PATCH v2 4/7] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper

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Message-ID: <87wm6gzwsu.ffs@tglx>
Date: Tue, 02 Sep 2025 17:41:37 +0200
From: Thomas Gleixner <tglx@...utronix.de>
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>, Sean Christopherson <seanjc@...gle.com>, Paolo
 Bonzini <pbonzini@...hat.com>, 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, Nuno Das Neves
 <nunodasneves@...ux.microsoft.com>, Mukesh R <mrathor@...ux.microsoft.com>
Subject: Re: [PATCH v2 4/7] entry/kvm: KVM: Move KVM details related to
 signal/-EINTR into KVM proper

On Wed, Aug 27 2025 at 17:01, Sean Christopherson wrote:
> Move KVM's morphing of pending signals into userspace exits into KVM
> proper, and drop the @vcpu param from xfer_to_guest_mode_handle_work().
> How KVM responds to -EINTR is a detail that really belongs in KVM itself,
> and invoking kvm_handle_signal_exit() from kernel code creates an inverted
> module dependency.  E.g. attempting to move kvm_handle_signal_exit() into
> kvm_main.c would generate an linker error when building kvm.ko as a module.
>
> Dropping KVM details will also converting the KVM "entry" code into a more
> generic virtualization framework so that it can be used when running as a
> Hyper-V root partition.
>
> Lastly, eliminating usage of "struct kvm_vcpu" outside of KVM is also nice
> to have for KVM x86 developers, as keeping the details of kvm_vcpu purely
> within KVM allows changing the layout of the structure without having to
> boot into a new kernel, e.g. allows rebuilding and reloading kvm.ko with a
> modified kvm_vcpu structure as part of debug/development.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>