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

Ankur Arora
2024-05-28T00:36:17Z

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@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.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