This is a note to let you know that I've just added the patch titled
KVM: remember position in kvm->vcpus array
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-remember-position-in-kvm-vcpus-array.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8750e72a79dda2f665ce17b62049f4d62130d991 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@xxxxxxxxxx>
Date: Thu, 7 Nov 2019 07:53:42 -0500
Subject: KVM: remember position in kvm->vcpus array
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From: Radim Krčmář <rkrcmar@xxxxxxxxxx>
commit 8750e72a79dda2f665ce17b62049f4d62130d991 upstream.
Fetching an index for any vcpu in kvm->vcpus array by traversing
the entire array everytime is costly.
This patch remembers the position of each vcpu in kvm->vcpus array
by storing it in vcpus_idx under kvm_vcpu structure.
Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Signed-off-by: Nitesh Narayan Lal <nitesh@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[borntraeger@xxxxxxxxxx]: backport to 4.19 (also fits for 5.4)
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/kvm_host.h | 11 +++--------
virt/kvm/kvm_main.c | 5 +++--
2 files changed, 6 insertions(+), 10 deletions(-)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -266,7 +266,8 @@ struct kvm_vcpu {
struct preempt_notifier preempt_notifier;
#endif
int cpu;
- int vcpu_id;
+ int vcpu_id; /* id given by userspace at creation */
+ int vcpu_idx; /* index in kvm->vcpus array */
int srcu_idx;
int mode;
u64 requests;
@@ -571,13 +572,7 @@ static inline struct kvm_vcpu *kvm_get_v
static inline int kvm_vcpu_get_idx(struct kvm_vcpu *vcpu)
{
- struct kvm_vcpu *tmp;
- int idx;
-
- kvm_for_each_vcpu(idx, tmp, vcpu->kvm)
- if (tmp == vcpu)
- return idx;
- BUG();
+ return vcpu->vcpu_idx;
}
#define kvm_for_each_memslot(memslot, slots) \
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2864,7 +2864,8 @@ static int kvm_vm_ioctl_create_vcpu(stru
goto unlock_vcpu_destroy;
}
- BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);
+ vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus);
+ BUG_ON(kvm->vcpus[vcpu->vcpu_idx]);
/* Now it's all set up, let userspace reach it */
kvm_get_kvm(kvm);
@@ -2874,7 +2875,7 @@ static int kvm_vm_ioctl_create_vcpu(stru
goto unlock_vcpu_destroy;
}
- kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;
+ kvm->vcpus[vcpu->vcpu_idx] = vcpu;
/*
* Pairs with smp_rmb() in kvm_get_vcpu. Write kvm->vcpus
Patches currently in stable-queue which might be from rkrcmar@xxxxxxxxxx are
queue-5.4/kvm-remember-position-in-kvm-vcpus-array.patch
