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

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Message-ID: <20250825222319.GO3419281@noisy.programming.kicks-ass.net>
Date: Tue, 26 Aug 2025 00:23:19 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: 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>,
	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>, 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 Mon, Aug 25, 2025 at 01:06:17PM -0700, 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.

I suspect there's more of this wreckage in the new VTL driver that
they just put in:

  https://lore.kernel.org/all/20250729051436.190703-3-namjain@linux.microsoft.com/

although ideally they rip that thing out. I don't know how that code can
ever be correct.