Messages in this thread | | | Date | Mon, 13 Dec 2021 16:46:07 +0100 | Subject | Re: [PATCH v5 1/1] s390x: KVM: accept STSI for CPU topology information | From | Pierre Morel <> |
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On 12/13/21 16:21, Heiko Carstens wrote: > On Mon, Dec 13, 2021 at 03:26:58PM +0100, Pierre Morel wrote: >>> Why is this assumption necessary? The statement that Linux runs only >>> with horizontal polarization is not true. >>> >> >> Right, I will rephrase this as: >> >> "Polarization change is not taken into account, QEMU intercepts queries for >> polarization change (PTF) and only provides horizontal polarization >> indication to Guest's Linux." >> >> @Heiko, I did not find any usage of the polarization in the kernel other >> than an indication in the sysfs. Is there currently other use of the >> polarization that I did not see? > > You can change polarization by writing to /sys/devices/system/cpu/dispatching. > > Or alternativel use the chcpu tool to change polarization. There is > however no real support for vertical polarization implemented in the > kernel. Therefore changing to vertical polarization is _not_ > recommended, since it will most likely have negative performance > impacts on your Linux system. > However the interface is still there for experimental purposes. >
Thanks, so I guess that not reflecting polarization changes to the guest topology will be OK for the moment. Of course, I will change the wrong comment.
-- Pierre Morel IBM Lab Boeblingen
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