[libvirt] [PATCH 4/4] qemu: Add support for setting the TSEG size

[Laszlo Ersek]

On 06/07/18 21:58, Ján Tomko wrote:

> Does a size of 0 MiB make sense? It's divisible by 1 MiB.

"-global mch.extended-tseg-mbytes=0" makes QEMU behave as if it lacked
the extended TSEG feature; the guest will believe that only the standard
1 / 2 / 8 MB TSEG sizes are available, and pick one of those.

Technically, in QEMU the extended TSEG feature is disabled for older
machine types by setting "mch.extended-tseg-mbytes" to zero:

[include/hw/i386/pc.h]

#define PC_COMPAT_2_9 \
    HW_COMPAT_2_9 \
    {\
        .driver   = "mch",\
        .property = "extended-tseg-mbytes",\
        .value    = stringify(0),\
    },\

I'm unsure whether this -- i.e., disabling the feature -- is useful to
expose through the domain config. Probably not.

Thanks
Laszlo