linux-kernel - [PATCH v2 3/7] Drivers: hv: Disable IRQs only after handling pending work before VTL return

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Message-ID: <20250828000156.23389-4-seanjc@google.com>
Date: Wed, 27 Aug 2025 17:01:52 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: 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>, 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, 
	Nuno Das Neves <nunodasneves@...ux.microsoft.com>, Mukesh R <mrathor@...ux.microsoft.com>
Subject: [PATCH v2 3/7] Drivers: hv: Disable IRQs only after handling pending
 work before VTL return

Swap the order of checking for TIF-based work and cancellation, and disable
IRQs only after checking and processing TIF-based work; checking TIF with
IRQs enabled is a-ok, e.g. IRQs and preemption _must_ be enabled before
handling the pending work.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 drivers/hv/mshv_vtl_main.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index aa09a76f0eff..4ca13c54c0a0 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -735,16 +735,8 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 		struct hv_vp_assist_page *hvp;
 		int ret;
 
-		local_irq_save(irq_flags);
-		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
-			local_irq_restore(irq_flags);
-			preempt_enable();
-			return -EINTR;
-		}
-
 		ti_work = READ_ONCE(current_thread_info()->flags);
 		if (unlikely(ti_work & VTL0_WORK)) {
-			local_irq_restore(irq_flags);
 			preempt_enable();
 			ret = mshv_do_pre_guest_mode_work(ti_work);
 			if (ret)
@@ -753,6 +745,13 @@ static int mshv_vtl_ioctl_return_to_lower_vtl(void)
 			continue;
 		}
 
+		local_irq_save(irq_flags);
+		if (READ_ONCE(mshv_vtl_this_run()->cancel)) {
+			local_irq_restore(irq_flags);
+			preempt_enable();
+			return -EINTR;
+		}
+
 		mshv_vtl_return(&mshv_vtl_this_run()->cpu_context);
 		local_irq_restore(irq_flags);
 
-- 
2.51.0.268.g9569e192d0-goog