linux-kernel - [PATCH v2 09/35] entry/kvm: handle lazy rescheduling at guest-entry

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Message-Id: <20240528003521.979836-10-ankur.a.arora@oracle.com>
Date: Mon, 27 May 2024 17:34:55 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-kernel@...r.kernel.org
Cc: tglx@...utronix.de, peterz@...radead.org, torvalds@...ux-foundation.org,
        paulmck@...nel.org, rostedt@...dmis.org, mark.rutland@....com,
        juri.lelli@...hat.com, joel@...lfernandes.org, raghavendra.kt@....com,
        sshegde@...ux.ibm.com, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com, Ankur Arora <ankur.a.arora@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 09/35] entry/kvm: handle lazy rescheduling at guest-entry

Archs defining CONFIG_KVM_XFER_TO_GUEST_WORK call
xfer_to_guest_mode_handle_work() from various KVM vcpu-run
loops to check for any task work including rescheduling.

Handle TIF_NEED_RESCHED_LAZY alongside TIF_NEED_RESCHED.

Also, while at it, remove the explicit check for need_resched() in
the exit condition as that is already covered in the loop condition.

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>
Originally-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/
Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 include/linux/entry-kvm.h | 2 +-
 kernel/entry/kvm.c        | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 6813171afccb..674a622c91be 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -18,7 +18,7 @@
 
 #define XFER_TO_GUEST_MODE_WORK						\
 	(_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL |	\
-	 _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)
+	 _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED_LAZY | ARCH_XFER_TO_GUEST_MODE_WORK)
 
 struct kvm_vcpu;
 
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 2e0f75bcb7fd..8485f63863af 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -13,7 +13,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 			return -EINTR;
 		}
 
-		if (ti_work & _TIF_NEED_RESCHED)
+		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
 			schedule();
 
 		if (ti_work & _TIF_NOTIFY_RESUME)
@@ -24,7 +24,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 			return ret;
 
 		ti_work = read_thread_flags();
-	} while (ti_work & XFER_TO_GUEST_MODE_WORK || need_resched());
+	} while (ti_work & XFER_TO_GUEST_MODE_WORK);
 	return 0;
 }
 
-- 
2.31.1