From: Paolo Bonzini <pbonzini@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: "Radim Krčmář" <rkrcmar@redhat.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
"Wanpeng Li" <wanpengli@tencent.com>,
"Jim Mattson" <jmattson@google.com>,
"Joerg Roedel" <joro@8bytes.org>
Subject: Re: [PATCH 2/2] KVM: LAPIC: micro-optimize fixed mode ipi delivery
Date: Mon, 11 Nov 2019 22:59:08 +0100 [thread overview]
Message-ID: <7a526814-c44e-c188-fba4-c6fb97b88b71@redhat.com> (raw)
In-Reply-To: <1573283135-5502-2-git-send-email-wanpengli@tencent.com>
On 09/11/19 08:05, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> After disabling mwait/halt/pause vmexits, RESCHEDULE_VECTOR and
> CALL_FUNCTION_SINGLE_VECTOR etc IPI is one of the main remaining
> cause of vmexits observed in product environment which can't be
> optimized by PV IPIs. This patch is the follow-up on commit
> 0e6d242eccdb (KVM: LAPIC: Micro optimize IPI latency), to optimize
> redundancy logic before fixed mode ipi is delivered in the fast
> path.
>
> - broadcast handling needs to go slow path, so the delivery mode repair
> can be delayed to before slow path.
I agree with this part, but is the cost of the irq->shorthand check
really measurable?
Paolo
> - self-IPI will not be intervened by hypervisor any more after APICv is
> introduced and the boxes support APICv are popular now. In addition,
> kvm_apic_map_get_dest_lapic() can handle the self-IPI, so there is no
> need a shortcut for the non-APICv case.
>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> arch/x86/kvm/irq_comm.c | 6 +++---
> arch/x86/kvm/lapic.c | 5 -----
> 2 files changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> index 8ecd48d..aa88156 100644
> --- a/arch/x86/kvm/irq_comm.c
> +++ b/arch/x86/kvm/irq_comm.c
> @@ -52,15 +52,15 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> unsigned long dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)];
> unsigned int dest_vcpus = 0;
>
> + if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map))
> + return r;
> +
> if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
> kvm_lowest_prio_delivery(irq)) {
> printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
> irq->delivery_mode = APIC_DM_FIXED;
> }
>
> - if (kvm_irq_delivery_to_apic_fast(kvm, src, irq, &r, dest_map))
> - return r;
> -
> memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap));
>
> kvm_for_each_vcpu(i, vcpu, kvm) {
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index b29d00b..ea936fa 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -951,11 +951,6 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
>
> *r = -1;
>
> - if (irq->shorthand == APIC_DEST_SELF) {
> - *r = kvm_apic_set_irq(src->vcpu, irq, dest_map);
> - return true;
> - }
> -
> rcu_read_lock();
> map = rcu_dereference(kvm->arch.apic_map);
>
>
next prev parent reply other threads:[~2019-11-11 21:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-09 7:05 [PATCH 1/2] KVM: X86: Single target IPI fastpath Wanpeng Li
2019-11-09 7:05 ` [PATCH 2/2] KVM: LAPIC: micro-optimize fixed mode ipi delivery Wanpeng Li
2019-11-11 21:59 ` Paolo Bonzini [this message]
2019-11-12 1:34 ` Wanpeng Li
2019-11-10 1:59 ` [PATCH 1/2] KVM: X86: Single target IPI fastpath kbuild test robot
2019-11-10 1:59 ` [PATCH] KVM: X86: fix semicolon.cocci warnings kbuild test robot
2019-11-11 13:06 ` [PATCH 1/2] KVM: X86: Single target IPI fastpath Vitaly Kuznetsov
2019-11-12 1:18 ` Wanpeng Li
2019-11-11 21:59 ` Paolo Bonzini
2019-11-12 1:33 ` Wanpeng Li
2019-11-13 6:05 ` Wanpeng Li
2019-11-14 3:12 ` Wanpeng Li
2019-11-14 11:58 ` Paolo Bonzini
2019-11-14 15:22 ` Sean Christopherson
2019-11-14 15:44 ` Paolo Bonzini
2019-11-14 16:34 ` Sean Christopherson
2019-11-15 5:56 ` Wanpeng Li
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7a526814-c44e-c188-fba4-c6fb97b88b71@redhat.com \
--to=pbonzini@redhat.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kernellwp@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=rkrcmar@redhat.com \
--cc=sean.j.christopherson@intel.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).