linux-kernel - [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv

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Message-ID: <20250825200622.3759571-2-seanjc@google.com>
Date: Mon, 25 Aug 2025 13:06:18 -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
Subject: [PATCH 1/5] Drivers: hv: Move TIF pre-guest work handling fully into mshv_common.c

Move the root partition's handling of pending thread work fully into
mshv_common.c so that the "work pending" and "do work" code is co-located.
Splitting the flags-to-check logic makes the code unnnecessarily difficult
to maintain, e.g. it would be all too easy to add a check in "do work" but
not in "work pending", and vice versa.

Note, this adds an extra CALL+RET when no work is pending; that will be
remedied in the near feature by switching to common virtualization entry
APIs.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 drivers/hv/mshv.h           |  2 +-
 drivers/hv/mshv_common.c    | 24 +++++++++++++++++++++++-
 drivers/hv/mshv_root_main.c | 24 +-----------------------
 3 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/drivers/hv/mshv.h b/drivers/hv/mshv.h
index 0340a67acd0a..db3aa3831c43 100644
--- a/drivers/hv/mshv.h
+++ b/drivers/hv/mshv.h
@@ -25,6 +25,6 @@ int hv_call_set_vp_registers(u32 vp_index, u64 partition_id, u16 count,
 int hv_call_get_partition_property(u64 partition_id, u64 property_code,
 				   u64 *property_value);
 
-int mshv_do_pre_guest_mode_work(ulong th_flags);
+int mshv_do_pre_guest_mode_work(void);
 
 #endif /* _MSHV_H */
diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
index 6f227a8a5af7..1acc47c4be0d 100644
--- a/drivers/hv/mshv_common.c
+++ b/drivers/hv/mshv_common.c
@@ -146,7 +146,7 @@ EXPORT_SYMBOL_GPL(hv_call_get_partition_property);
  *
  * Returns: 0 on success, -errno on error.
  */
-int mshv_do_pre_guest_mode_work(ulong th_flags)
+static int __mshv_do_pre_guest_mode_work(ulong th_flags)
 {
 	if (th_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 		return -EINTR;
@@ -159,4 +159,26 @@ int mshv_do_pre_guest_mode_work(ulong th_flags)
 
 	return 0;
 }
+
+int mshv_do_pre_guest_mode_work(void)
+{
+	const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
+				 _TIF_NEED_RESCHED  | _TIF_NOTIFY_RESUME;
+	ulong th_flags;
+
+	th_flags = read_thread_flags();
+	while (th_flags & work_flags) {
+		int ret;
+
+		/* nb: following will call schedule */
+		ret = __mshv_do_pre_guest_mode_work(th_flags);
+		if (ret)
+			return ret;
+
+		th_flags = read_thread_flags();
+	}
+
+	return 0;
+
+}
 EXPORT_SYMBOL_GPL(mshv_do_pre_guest_mode_work);
diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index 72df774e410a..6f677fb93af0 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -487,28 +487,6 @@ mshv_vp_wait_for_hv_kick(struct mshv_vp *vp)
 	return 0;
 }
 
-static int mshv_pre_guest_mode_work(struct mshv_vp *vp)
-{
-	const ulong work_flags = _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING |
-				 _TIF_NEED_RESCHED  | _TIF_NOTIFY_RESUME;
-	ulong th_flags;
-
-	th_flags = read_thread_flags();
-	while (th_flags & work_flags) {
-		int ret;
-
-		/* nb: following will call schedule */
-		ret = mshv_do_pre_guest_mode_work(th_flags);
-
-		if (ret)
-			return ret;
-
-		th_flags = read_thread_flags();
-	}
-
-	return 0;
-}
-
 /* Must be called with interrupts enabled */
 static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
 {
@@ -529,7 +507,7 @@ static long mshv_run_vp_with_root_scheduler(struct mshv_vp *vp)
 		u32 flags = 0;
 		struct hv_output_dispatch_vp output;
 
-		ret = mshv_pre_guest_mode_work(vp);
+		ret = mshv_do_pre_guest_mode_work();
 		if (ret)
 			break;
 
-- 
2.51.0.261.g7ce5a0a67e-goog