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Re: [Qemu-devel] [PATCH v3 0/2] Allow migration with invtsc if TSC frequ
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] [PATCH v3 0/2] Allow migration with invtsc if TSC frequency is explicitly set |
Date: |
Wed, 18 Jan 2017 10:11:31 -0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sun, Jan 08, 2017 at 03:32:32PM -0200, Eduardo Habkost wrote:
> This series makes QEMU accept migration if tsc-frequency is
> explicitly set on configuration. As management software is
> required to keep device configuration the same on migration
> source or destination, explicit tsc-frequency will ensure that
> either:
>
> * The destination host has a matching TSC frequency; or
> * The destination host has TSC scaling available.
>
> Changelog
> =========
>
> v2 -> v3:
> * Fix build failure ((missing closing braces)
>
> v1 -> v2:
> * v1 series subject was:
> * [PATCH 0/4] Allow migration with invtsc if there's no
> frequency mismatch
> * Removed patches 3/4 and 4/4, that allowed migration
> if no explicit tsc-frequency was set. Implementing the check on
> post_load or post_init is not enough to make migration abort,
> so we will need a more complex solution to implement that
> feature.
>
> Plans for future work
> =====================
>
> 1) Querying host TSC frequency/scaling capability
> -------------------------------------------------
>
> I plan to include TSC frequency/scaling information on
> query-cpu-model-expansion model="host" in a future series. Then
> management software will be able to automatically configure TSC
> frequency when invtsc is enabled, instead of requiring the user
> to configure it explicitly. While we don't implement that, invtsc
> migration will be possible only if the user configures TSC
> frequency manually.
>
> 2) invtsc migration with no explicit TSC frequency
> --------------------------------------------------
>
> A future series can implement migration when TSC frequency is not
> specified explicitly. It will be a bit more complex because it
> requires either letting the destination abort the migration, or
> sending TSC frequency/scaling information from destination to
> source.
>
> ---
> Cc: Marcelo Tosatti <address@hidden>
> Cc: "Daniel P. Berrange" <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Cc: address@hidden
> Cc: Haozhong Zhang <address@hidden>
> Cc: "Michael S. Tsirkin" <address@hidden>
> Cc: Igor Mammedov <address@hidden>
> Cc: address@hidden
> Cc: Jiri Denemark <address@hidden>
>
> Eduardo Habkost (2):
> kvm: Simplify invtsc check
> kvm: Allow invtsc migration if tsc-khz is set explicitly
>
> target/i386/kvm.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> --
> 2.11.0.259.g40922b1
Looks good to me.