[PATCH] docs: Update xen-tscmode.pod.7 to reflect default TSC mode changes

[PATCH] docs: Update xen-tscmode.pod.7 to reflect default TSC mode changes

[Boris Ostrovsky]

A number of changes have been made to how we determine whether TSC
is emulated (e.g. commit 4fc380ac0077 ("x86/time: don't use virtual TSC
if host and guest frequencies are equal")).

Update the man page to reflect those changes

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Suggested-by: Olaf Hering <olaf@aepfle.de>
---
 docs/man/xen-tscmode.pod.7 | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/docs/man/xen-tscmode.pod.7 b/docs/man/xen-tscmode.pod.7
index 0da57e5..0f93453 100644
--- a/docs/man/xen-tscmode.pod.7
+++ b/docs/man/xen-tscmode.pod.7
@@ -203,12 +203,12 @@ 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.
+however, there are two possibilities: TSC remains native IF the source
+physical machine and target physical machine have the same TSC frequency
+(or, for HVM/PVH guests, if TSC scaling support is available); 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.
 
 For environments where both TSC-safeness AND highest performance
 even across migration is a requirement, application code can be specially
-- 
2.7.4


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Re: [PATCH] docs: Update xen-tscmode.pod.7 to reflect default TSC mode changes

[Wei Liu]

On Wed, Mar 29, 2017 at 10:49:34AM -0400, Boris Ostrovsky wrote:
> A number of changes have been made to how we determine whether TSC
> is emulated (e.g. commit 4fc380ac0077 ("x86/time: don't use virtual TSC
> if host and guest frequencies are equal")).
> 
> Update the man page to reflect those changes
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Suggested-by: Olaf Hering <olaf@aepfle.de>

Acked-by: Wei Liu <wei.liu2@citrix.com>

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