From: Sean Christopherson <seanjc@google.com>
To: Marc Zyngier <maz@kernel.org>,
Oliver Upton <oliver.upton@linux.dev>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Tianrui Zhao <zhaotianrui@loongson.cn>,
Bibo Mao <maobibo@loongson.cn>,
Huacai Chen <chenhuacai@kernel.org>,
Anup Patel <anup@brainfault.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Joel Fernandes <joelagnelf@nvidia.com>,
Josh Triplett <josh@joshtriplett.org>,
Boqun Feng <boqun.feng@gmail.com>,
Uladzislau Rezki <urezki@gmail.com>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
kvm@vger.kernel.org, loongarch@lists.linux.dev,
kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
linux-hyperv@vger.kernel.org, rcu@vger.kernel.org
Subject: [PATCH 2/5] Drivers: hv: Handle NEED_RESCHED_LAZY before transferring to guest
Date: Mon, 25 Aug 2025 13:06:19 -0700 [thread overview]
Message-ID: <20250825200622.3759571-3-seanjc@google.com> (raw)
In-Reply-To: <20250825200622.3759571-1-seanjc@google.com>
Check for NEED_RESCHED_LAZY, not just NEED_RESCHED, prior to transferring
control to a guest. Failure to check for lazy resched can unnecessarily
delay rescheduling until the next tick when using a lazy preemption model.
Fixes: 621191d709b1 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
drivers/hv/mshv_common.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index 1acc47c4be0d..b953b5e21110 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -151,7 +151,7 @@ static int __mshv_do_pre_guest_mode_work(ulong th_flags)
if (th_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
return -EINTR;
- if (th_flags & _TIF_NEED_RESCHED)
+ if (th_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
schedule();
if (th_flags & _TIF_NOTIFY_RESUME)
@@ -163,7 +163,8 @@ static int __mshv_do_pre_guest_mode_work(ulong th_flags)
int mshv_do_pre_guest_mode_work(void)
{
const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
- _TIF_NEED_RESCHED | _TIF_NOTIFY_RESUME;
+ _TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY |
+ _TIF_NOTIFY_RESUME;
ulong th_flags;
th_flags = read_thread_flags();
--
2.51.0.261.g7ce5a0a67e-goog
next prev parent reply other threads:[~2025-08-25 20:06 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-25 20:06 [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Sean Christopherson
2025-08-25 20:06 ` [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c Sean Christopherson
2025-08-25 20:06 ` Sean Christopherson [this message]
2025-08-25 20:06 ` [PATCH 3/5] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper Sean Christopherson
2025-08-25 20:06 ` [PATCH 4/5] entry: Rename "kvm" entry code assets to "virt" to genericize APIs Sean Christopherson
2025-08-25 20:06 ` [PATCH 5/5] Drivers: hv: Use common "entry virt" APIs to do work before running guest Sean Christopherson
2025-08-25 21:45 ` [PATCH 0/5] Drivers: hv: Fix NEED_RESCHED_LAZY and use common APIs Wei Liu
2025-08-25 22:23 ` Peter Zijlstra
2025-08-25 22:26 ` Wei Liu
2025-08-25 23:08 ` Nuno Das Neves
2025-08-26 0:27 ` Sean Christopherson
2025-08-26 16:58 ` Wei Liu
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