public inbox for kvm@vger.kernel.org
 help / color / mirror / Atom feed
From: bugzilla-daemon@bugzilla.kernel.org
To: kvm@vger.kernel.org
Subject: [Bug 116011] New: After hot plug vcpu, kvm_arch->use_master_clock will never be true.
Date: Thu, 07 Apr 2016 07:42:14 +0000	[thread overview]
Message-ID: <bug-116011-28872@https.bugzilla.kernel.org/> (raw)

https://bugzilla.kernel.org/show_bug.cgi?id=116011

            Bug ID: 116011
           Summary: After hot plug vcpu, kvm_arch->use_master_clock will
                    never be true.
           Product: Virtualization
           Version: unspecified
    Kernel Version: 4.5
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: changlimin@h3c.com
        Regression: No

1. In function kvm_write_tsc, when tsc first matched, do
kvm->arch.nr_vcpus_matched_tsc++;

2. In function pvclock_update_vm_gtod_copy, if vcpus_matched (also with other
conditions meet), ka->use_master_clock will be true;

3. After hot plug vcpu, kvm_arch_vcpu_postcreate and Qemu will call
kvm_write_tsc for the new vcpu. Because the tsc will not match, so do
kvm->arch.nr_vcpus_matched_tsc = 0;

4. For other already existed vcpu will not call kvm_write_tsc, so will not do
kvm->arch.nr_vcpus_matched_tsc++;

5. So vcpus_matched in function pvclock_update_vm_gtod_copy will be false
forever, this cause ka->use_master_clock will never be true;

-- 
You are receiving this mail because:
You are watching the assignee of the bug.

                 reply	other threads:[~2016-04-07  7:42 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

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=bug-116011-28872@https.bugzilla.kernel.org/ \
    --to=bugzilla-daemon@bugzilla.kernel.org \
    --cc=kvm@vger.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