spapr: Limit available pagesizes to provide a consistent guest environment
KVM HV has some limitations (deriving from the hardware) that mean not all host-cpu supported pagesizes may be usable in the guest. At present this means that KVM guests and TCG guests may see different available page sizes even if they notionally have the same vcpu model. This is confusing and also prevents migration between TCG and KVM. This patch makes the environment consistent by always allowing the same set of pagesizes. Since we can't remove the KVM limitations, we do this by always applying the same limitations it has, even to TCG guests. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Cédric Le Goater <clg@kaod.org> Reviewed-by: Greg Kurz <groug@kaod.org>
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@ -335,6 +335,39 @@ static void cap_hpt_maxpagesize_apply(sPAPRMachineState *spapr,
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spapr_check_pagesize(spapr, qemu_getrampagesize(), errp);
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}
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static bool spapr_pagesize_cb(void *opaque, uint32_t seg_pshift,
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uint32_t pshift)
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{
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unsigned maxshift = *((unsigned *)opaque);
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assert(pshift >= seg_pshift);
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/* Don't allow the guest to use pages bigger than the configured
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* maximum size */
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if (pshift > maxshift) {
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return false;
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}
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/* For whatever reason, KVM doesn't allow multiple pagesizes
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* within a segment, *except* for the case of 16M pages in a 4k or
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* 64k segment. Always exclude other cases, so that TCG and KVM
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* guests see a consistent environment */
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if ((pshift != seg_pshift) && (pshift != 24)) {
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return false;
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}
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return true;
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}
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static void cap_hpt_maxpagesize_cpu_apply(sPAPRMachineState *spapr,
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PowerPCCPU *cpu,
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uint8_t val, Error **errp)
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{
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unsigned maxshift = val;
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ppc_hash64_filter_pagesizes(cpu, spapr_pagesize_cb, &maxshift);
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}
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sPAPRCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
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[SPAPR_CAP_HTM] = {
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.name = "htm",
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@ -402,6 +435,7 @@ sPAPRCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
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.set = spapr_cap_set_pagesize,
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.type = "int",
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.apply = cap_hpt_maxpagesize_apply,
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.cpu_apply = cap_hpt_maxpagesize_cpu_apply,
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},
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};
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