Am Fri, 17 Mar 2017 14:15:26 -0400 schrieb Boris Ostrovsky <boris.ostrov...@oracle.com>:
> Commit 82713ec8d2 ("x86: use native RDTSC(P) execution when guest and
> host frequencies are the same") left out optimization for PV guests
> when host and guest run at the same frequency.
>
> For such a case we should be able not to use virtual TSC regardless
> of whether we are runing before or after a migration (i.e. regardless
> of incarnation value).
I think this part of tscmode.txt may needs an update now.
Doesn't the "always emulated for PV" meant the part which was changed?
...
The default mode (tsc_mode==0) checks TSC-safeness of the underlying
hardware on which the virtual machine is launched. If it is
TSC-safe, rdtsc will execute at hardware speed; if it is not, rdtsc
will be emulated. Once a virtual machine is save/restored or migrated,
however, there are two possibilities: For a paravirtualized (PV) domain,
TSC will always be emulated. For a fully-virtualized (HVM) domain,
TSC remains native IF the source physical machine and target physical machine
have the same TSC frequency; else TSC is emulated. Note that, though
emulated, the "apparent" TSC frequency will be the TSC frequency
of the initial physical machine, even after migration.
...
Olaf
pgpDlcpU5Idhn.pgp
Description: Digitale Signatur von OpenPGP
_______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
