On Tue, 19 Jan 2021 10:14:55 +0530 Bharata B Rao <bhar...@linux.ibm.com> wrote:
> On Fri, Jan 15, 2021 at 06:30:05PM +0100, Greg Kurz wrote: > > On Fri, 15 Jan 2021 14:01:28 +0530 > > Bharata B Rao <bhar...@linux.ibm.com> wrote: > > > > > On Wed, Jan 13, 2021 at 05:22:56PM +0100, Greg Kurz wrote: > > > > Hi Bharata, > > > > > > > > On Wed, 6 Jan 2021 14:29:10 +0530 > > > > Bharata B Rao <bhar...@linux.ibm.com> wrote: > > > > > > > > > If KVM_CAP_RPT_INVALIDATE KVM capability is enabled, then > > > > > > > > > > - indicate the availability of H_RPT_INVALIDATE hcall to the guest via > > > > > ibm,hypertas-functions property. > > > > > - Enable the hcall > > > > > > > > > > Both the above are done only if the new sPAPR machine capability > > > > > cap-rpt-invalidate is set. > > > > > > > > > > Note: The KVM implementation of the hcall has been posted for upstream > > > > > review here: > > > > > https://lore.kernel.org/linuxppc-dev/20210105090557.2150104-1-bhar...@linux.ibm.com/T/#t > > > > > > > > > > Update to linux-headers/linux/kvm.h here is temporary, will be > > > > > done via header updates once the kernel change is accepted upstream. > > > > > > > > > > Signed-off-by: Bharata B Rao <bhar...@linux.ibm.com> > > > > > --- > > > > > > > > Patch looks mostly fine. A few remarks below. > > > > > > > > > hw/ppc/spapr.c | 7 ++++++ > > > > > hw/ppc/spapr_caps.c | 49 > > > > > +++++++++++++++++++++++++++++++++++++++ > > > > > include/hw/ppc/spapr.h | 8 +++++-- > > > > > linux-headers/linux/kvm.h | 1 + > > > > > target/ppc/kvm.c | 12 ++++++++++ > > > > > target/ppc/kvm_ppc.h | 11 +++++++++ > > > > > 6 files changed, 86 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > > > > > index 489cefcb81..0228083800 100644 > > > > > --- a/hw/ppc/spapr.c > > > > > +++ b/hw/ppc/spapr.c > > > > > @@ -890,6 +890,11 @@ static void spapr_dt_rtas(SpaprMachineState > > > > > *spapr, void *fdt) > > > > > add_str(hypertas, "hcall-copy"); > > > > > add_str(hypertas, "hcall-debug"); > > > > > add_str(hypertas, "hcall-vphn"); > > > > > + if (kvm_enabled() && > > > > > > > > You shouldn't check KVM here. The capability is enough to decide if we > > > > should expose "hcall-rpt-invalidate" or not. FWIW we won't even reach > > > > this code when running with anything but KVM. > > > > > > Correct, the capability itself can be only for KVM case. > > > > > > > > > > > > + (spapr_get_cap(spapr, SPAPR_CAP_RPT_INVALIDATE) == > > > > > SPAPR_CAP_ON)) { > > > > > + add_str(hypertas, "hcall-rpt-invalidate"); > > > > > + } > > > > > + > > > > > add_str(qemu_hypertas, "hcall-memop1"); > > > > > > > > > > if (!kvm_enabled() || kvmppc_spapr_use_multitce()) { > > > > > @@ -2021,6 +2026,7 @@ static const VMStateDescription vmstate_spapr = > > > > > { > > > > > &vmstate_spapr_cap_ccf_assist, > > > > > &vmstate_spapr_cap_fwnmi, > > > > > &vmstate_spapr_fwnmi, > > > > > + &vmstate_spapr_cap_rpt_invalidate, > > > > > NULL > > > > > } > > > > > }; > > > > > @@ -4478,6 +4484,7 @@ static void > > > > > spapr_machine_class_init(ObjectClass *oc, void *data) > > > > > smc->default_caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = > > > > > SPAPR_CAP_ON; > > > > > smc->default_caps.caps[SPAPR_CAP_CCF_ASSIST] = SPAPR_CAP_ON; > > > > > smc->default_caps.caps[SPAPR_CAP_FWNMI] = SPAPR_CAP_ON; > > > > > + smc->default_caps.caps[SPAPR_CAP_RPT_INVALIDATE] = SPAPR_CAP_OFF; > > > > > > > > Any reason for not enabling this for the default machine type and > > > > disabling it for existing machine types only ? > > > > > > If this capability is enabled, then > > > > > > 1. First level guest (L1) can off-load the TLB invalidations to the > > > new hcall if the platform has disabled LPCR[GTSE]. > > > > > > 2. Nested guest (L2) will switch to this new hcall rather than using > > > the old H_TLB_INVALIDATE hcall. > > > > > > Case 2 is optional and case 1 makes sense only if LPCR[GTSE]=off. > > > > I don't think this is relevant, as the importance of each case can change, > > e.g. nested is gaining momentum. > > > > > Hence I thought keeping it off by default and expecting the > > > user to turn it on only if required would be correct. > > > > > > > If the feature is an improvement, even for what is considered a corner > > case now, and it doesn't do harm to setups that won't use it, then it > > should be enabled IMHO. > > > > > Please note that turning this capability ON will result in the > > > new hcall being exposed to the guest. I hope this is the right > > > usage of spapr-caps? > > > > > > > That's perfectly fine and this is why we should set it to ON > > for the default machine type only. > > The property can be turned ON only when the hypervisor supports > the hcall. So if it set to ON for default machine type, then > it may fail if the host doesn't have this hcall. Hence I thought > it should be OFF by default and turning ON should be left to the > user. > Ok. This can be changed later when H_RPT_INVALIDATE support is more widely available. BTW, if users are expected to manually set this, I think you should add some documentation so that they know how/when to use it. > Regards, > Bharata.
