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spapr: Handle VMX/VSX presence as an spapr capability flag

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We currently have some conditionals in the spapr device tree code to decide
whether or not to advertise the availability of the VMX (aka Altivec) and
VSX vector extensions to the guest, based on whether the guest cpu has
those features.

This can lead to confusion and subtle failures on migration, since it makes
a guest visible change based only on host capabilities.  We now have a
better mechanism for this, in spapr capabilities flags, which explicitly
depend on user options rather than host capabilities.

Rework the advertisement of VSX and VMX based on a new VSX capability.  We
no longer bother with a conditional for VMX support, because every CPU
that's ever been supported by the pseries machine type supports VMX.

NOTE: Some userspace distributions (e.g. RHEL7.4) already rely on
availability of VSX in libc, so using cap-vsx=off may lead to a fatal
SIGILL in init.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
This commit is contained in:
David Gibson 2017-12-07 17:08:47 +11:00
parent 3f2ca480eb
commit 2938664286
3 changed files with 39 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

20
hw/ppc/spapr.c
View file

@ -557,14 +557,16 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
segs, sizeof(segs))));
}
/* Advertise VMX/VSX (vector extensions) if available
* 0 / no property == no vector extensions
/* Advertise VSX (vector extensions) if available
* 1 == VMX / Altivec available
* 2 == VSX available */
if (env->insns_flags & PPC_ALTIVEC) {
uint32_t vmx = (env->insns_flags2 & PPC2_VSX) ? 2 : 1;
_FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", vmx)));
* 2 == VSX available
*
* Only CPUs for which we create core types in spapr_cpu_core.c
* are possible, and all of those have VMX */
if (spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
_FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", 2)));
} else {
_FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", 1)));
}
/* Advertise DFP (Decimal Floating Point) if available
@ -3832,7 +3834,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
*/
mc->numa_mem_align_shift = 28;
smc->default_caps = spapr_caps(0);
smc->default_caps = spapr_caps(SPAPR_CAP_VSX);
spapr_caps_add_properties(smc, &error_abort);
}
@ -3914,7 +3916,7 @@ static void spapr_machine_2_11_class_options(MachineClass *mc)
sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
spapr_machine_2_12_class_options(mc);
smc->default_caps = spapr_caps(SPAPR_CAP_HTM);
smc->default_caps = spapr_caps(SPAPR_CAP_HTM | SPAPR_CAP_VSX);
SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_11);
}