From: Yi Wang <up2wing@gmail.com>
To: seanjc@google.com, pbonzini@redhat.com, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, wanpengli@tencent.com,
foxywang@tencent.com, oliver.upton@linux.dev, maz@kernel.org,
anup@brainfault.org, atishp@atishpatra.org,
borntraeger@linux.ibm.com, frankja@linux.ibm.com,
imbrenda@linux.ibm.com, weijiang.yang@intel.com
Cc: up2wing@gmail.com
Subject: [v4 RESEND 0/3] KVM: irqchip: synchronize srcu only if needed
Date: Fri, 26 Apr 2024 12:15:56 +0800 [thread overview]
Message-ID: <20240426041559.3717884-1-foxywang@tencent.com> (raw)
From: Yi Wang <foxywang@tencent.com>
We found that it may cost more than 20 milliseconds very accidentally
to enable cap of KVM_CAP_SPLIT_IRQCHIP on a host which has many vms
already.
The reason is that when vmm(qemu/CloudHypervisor) invokes
KVM_CAP_SPLIT_IRQCHIP kvm will call synchronize_srcu_expedited() and
might_sleep and kworker of srcu may cost some delay during this period.
One way makes sence is setup empty irq routing when creating vm and
so that x86/s390 don't need to setup empty/dummy irq routing.
Note: I have no s390 machine so this patch has not been tested
thoroughly on s390 platform. Thanks to Christian for a quick test on
s390 and it still seems to work[1].
Changelog:
----------
v4:
- replace loop with memset when setup empty irq routing table.
v3:
- squash setup empty routing function and use of that into one commit
- drop the comment in s390 part
v2:
- setup empty irq routing in kvm_create_vm
- don't setup irq routing in x86 KVM_CAP_SPLIT_IRQCHIP
- don't setup irq routing in s390 KVM_CREATE_IRQCHIP
v1:
https://lore.kernel.org/kvm/20240112091128.3868059-1-foxywang@tencent.com/
1. https://lore.kernel.org/lkml/f898e36f-ba02-4c52-a3be-06caac13323e@linux.ibm.com/
Yi Wang (3):
KVM: setup empty irq routing when create vm
KVM: x86: don't setup empty irq routing when KVM_CAP_SPLIT_IRQCHIP
KVM: s390: don't setup dummy routing when KVM_CREATE_IRQCHIP
arch/s390/kvm/kvm-s390.c | 9 +--------
arch/x86/kvm/irq.h | 1 -
arch/x86/kvm/irq_comm.c | 5 -----
arch/x86/kvm/x86.c | 3 ---
include/linux/kvm_host.h | 1 +
virt/kvm/irqchip.c | 19 +++++++++++++++++++
virt/kvm/kvm_main.c | 4 ++++
7 files changed, 25 insertions(+), 17 deletions(-)
--
2.39.3
next reply other threads:[~2024-04-26 4:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 4:15 Yi Wang [this message]
2024-04-26 4:15 ` [v4 RESEND 1/3] KVM: setup empty irq routing when create vm Yi Wang
2024-05-03 22:08 ` Sean Christopherson
2024-05-05 4:56 ` Yi Wang
2024-04-26 4:15 ` [v4 RESEND 2/3] KVM: x86: don't setup empty irq routing when KVM_CAP_SPLIT_IRQCHIP Yi Wang
2024-04-26 4:15 ` [v4 RESEND 3/3] KVM: s390: don't setup dummy routing when KVM_CREATE_IRQCHIP Yi Wang
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=20240426041559.3717884-1-foxywang@tencent.com \
--to=up2wing@gmail.com \
--cc=anup@brainfault.org \
--cc=atishp@atishpatra.org \
--cc=borntraeger@linux.ibm.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=foxywang@tencent.com \
--cc=frankja@linux.ibm.com \
--cc=hpa@zytor.com \
--cc=imbrenda@linux.ibm.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maz@kernel.org \
--cc=mingo@redhat.com \
--cc=oliver.upton@linux.dev \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=wanpengli@tencent.com \
--cc=weijiang.yang@intel.com \
--cc=x86@kernel.org \
/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 read-only IMAP folder(s) and NNTP newsgroup(s).