On Fri, Dec 09, 2016 at 11:08:02AM -0600, Michael Roth wrote:
> Quoting David Gibson (2016-12-08 20:23:11)
> > This introduces stub implementations of the H_RESIZE_HPT_PREPARE and
> > H_RESIZE_HPT_COMMIT hypercalls which we hope to add in a PAPR
> > extension to allow run time resizing of a guest's hash page table. It
> > also adds a new machine property for controlling whether this new
> > facility is available, and logic to check that against availability
> > with KVM (only supported with KVM PR for now).
> >
> > Finally, it adds a new string to the hypertas property in the device
> > tree, advertising to the guest the availability of the HPT resizing
> > hypercalls. This is a tentative suggested value, and would need to be
> > standardized by PAPR before being merged.
> >
> > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> > ---
> > hw/ppc/spapr.c | 66
> > ++++++++++++++++++++++++++++++++++++++++++++++++++
> > hw/ppc/spapr_hcall.c | 36 +++++++++++++++++++++++++++
> > hw/ppc/trace-events | 2 ++
> > include/hw/ppc/spapr.h | 11 +++++++++
> > target-ppc/kvm.c | 26 ++++++++++++++++++++
> > target-ppc/kvm_ppc.h | 5 ++++
> > 6 files changed, 146 insertions(+)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 0f25e83..ecb0822 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -760,6 +760,11 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr,
> > void *fdt)
> > if (!kvm_enabled() || kvmppc_spapr_use_multitce()) {
> > add_str(hypertas, "hcall-multi-tce");
> > }
> > +
> > + if (spapr->resize_hpt != SPAPR_RESIZE_HPT_DISABLED) {
> > + add_str(hypertas, "hcall-hpt-resize");
> > + }
> > +
> > _FDT(fdt_setprop(fdt, rtas, "ibm,hypertas-functions",
> > hypertas->str, hypertas->len));
> > g_string_free(hypertas, TRUE);
> > @@ -1839,11 +1844,31 @@ static void ppc_spapr_init(MachineState *machine)
> > long load_limit, fw_size;
> > char *filename;
> > int smt = kvmppc_smt_threads();
> > + Error *resize_hpt_err = NULL;
> >
> > msi_nonbroken = true;
> >
> > QLIST_INIT(&spapr->phbs);
> >
> > + /* Check HPT resizing availability */
> > + kvmppc_check_papr_resize_hpt(&resize_hpt_err);
> > + if (spapr->resize_hpt == SPAPR_RESIZE_HPT_DEFAULT) {
> > + if (resize_hpt_err) {
> > + spapr->resize_hpt = SPAPR_RESIZE_HPT_DISABLED;
> > + error_free(resize_hpt_err);
> > + resize_hpt_err = NULL;
> > + } else {
> > + spapr->resize_hpt = smc->resize_hpt_default;
> > + }
> > + }
> > +
> > + assert(spapr->resize_hpt != SPAPR_RESIZE_HPT_DEFAULT);
> > +
> > + if ((spapr->resize_hpt != SPAPR_RESIZE_HPT_DISABLED) &&
> > resize_hpt_err) {
> > + error_report_err(resize_hpt_err);
> > + exit(1);
> > + }
>
> I'm also a bit confused by this. Aren't semantics that HPT_ENABLED will allow
> a fallback to non-resizable HPTs if the feature isn't available (whereas
> HPT_REQUIRED won't)? I don't understand how such a fallback can ever be
> reached
> with this check in place.
We fall back if the _guest_ doesn't support HPT resizing. This error
path is if the _host_ can't support HPT resizing. Some extra
information about this in the reply I'll shortly send to Thomas.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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