On Thu, Feb 13, 2020 at 04:38:38PM +0100, Greg Kurz wrote: > Until the CAS negotiation is over, an HPT can be allocated on three > different paths: > > 1) during machine reset if the host doesn't support radix, > > 2) during CAS if the guest wants hash and doesn't support HPT resizing, > in which case we pre-emptively resize the HPT to accomodate maxram, > > 3) during CAS if no CAS reboot was requested, the guest wants hash but > we're currently configured for radix. > > Depending on the various combinations of host or guest MMU support, > HPT resizing guest support and the possibility of a CAS reboot, it > is quite hard to know which of these allocates the HPT that will > be ultimately used by the guest that wants to do hash. Also, some of > them have bugs: > > - 2) calls spapr_reallocate_hpt() instead of spapr_setup_hpt_and_vrma() > and thus doesn't update the VRMA size, even though we've just extended > the HPT. Not sure what issues this can cause, > > - 3) doesn't check for HPT resizing support and will always allocate a > small HPT based on the initial RAM size. This caps the total amount of > RAM the guest can see, especially if maxram is much higher than the > initial ram. > > We only support guests that do CAS and we already assume that the HPT > isn't being used when we do the pre-emptive resizing at CAS. It thus > seems reasonable to only allocate the HPT at the end of CAS, when no > CAS reboot was requested. > > Consolidate the logic so that we only create the HPT during 3), ie. > when we're done with the CAS reboot cycles, and ensure HPT resizing > is taken into account. This fixes the radix->hash transition for > all cases. Uh.. I'm pretty sure this can't work for KVM on a POWER8 host. We need the HPT at all times there, or there's nowhere to put VRMA entries, so we can't run even in real mode. > The guest can theoretically call CAS several times, without a CAS > reboot in between. Linux guests don't do that, but better safe than > sorry, let's ensure we can also handle the symmetrical hash->radix > transition correctly: free the HPT and set the GR bit in PATE. > An helper is introduced for the latter since this is already what > we do during machine reset when going for radix. > > As a bonus, this removes one user of spapr->cas_reboot, which we > want to get rid of in the future. > > Signed-off-by: Greg Kurz > --- > hw/ppc/spapr.c | 25 +++++++++++++++----- > hw/ppc/spapr_hcall.c | 59 ++++++++++++++++++++---------------------------- > include/hw/ppc/spapr.h | 1 + > 3 files changed, 44 insertions(+), 41 deletions(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 828e2cc1359a..88bc0e4e3ca1 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1573,9 +1573,19 @@ void spapr_setup_hpt_and_vrma(SpaprMachineState *spapr) > { > int hpt_shift; > > + /* > + * HPT resizing is a bit of a special case, because when enabled > + * we assume an HPT guest will support it until it says it > + * doesn't, instead of assuming it won't support it until it says > + * it does. Strictly speaking that approach could break for > + * guests which don't make a CAS call, but those are so old we > + * don't care about them. Without that assumption we'd have to > + * make at least a temporary allocation of an HPT sized for max > + * memory, which could be impossibly difficult under KVM HV if > + * maxram is large. > + */ > if ((spapr->resize_hpt == SPAPR_RESIZE_HPT_DISABLED) > - || (spapr->cas_reboot > - && !spapr_ovec_test(spapr->ov5_cas, OV5_HPT_RESIZE))) { > + || !spapr_ovec_test(spapr->ov5_cas, OV5_HPT_RESIZE)) { > hpt_shift = spapr_hpt_shift_for_ramsize(MACHINE(spapr)->maxram_size); > } else { > uint64_t current_ram_size; > @@ -1604,6 +1614,12 @@ static int spapr_reset_drcs(Object *child, void *opaque) > return 0; > } > > +void spapr_reset_patb_entry(SpaprMachineState *spapr) > +{ > + spapr->patb_entry = PATE1_GR; > + spapr_set_all_lpcrs(LPCR_HR | LPCR_UPRT, LPCR_HR | LPCR_UPRT); > +} > + > static void spapr_machine_reset(MachineState *machine) > { > SpaprMachineState *spapr = SPAPR_MACHINE(machine); > @@ -1624,10 +1640,7 @@ static void spapr_machine_reset(MachineState *machine) > * without a HPT because KVM will start them in radix mode. > * Set the GR bit in PATE so that we know there is no HPT. > */ > - spapr->patb_entry = PATE1_GR; > - spapr_set_all_lpcrs(LPCR_HR | LPCR_UPRT, LPCR_HR | LPCR_UPRT); > - } else { > - spapr_setup_hpt_and_vrma(spapr); > + spapr_reset_patb_entry(spapr); > } > > qemu_devices_reset(); > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c > index b8bb66b5c0d4..57ddf0fa6d05 100644 > --- a/hw/ppc/spapr_hcall.c > +++ b/hw/ppc/spapr_hcall.c > @@ -1677,6 +1677,7 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu, > bool raw_mode_supported = false; > bool guest_xive; > CPUState *cs; > + int maxshift = spapr_hpt_shift_for_ramsize(MACHINE(spapr)->maxram_size); > > /* CAS is supposed to be called early when only the boot vCPU is active. */ > CPU_FOREACH(cs) { > @@ -1739,36 +1740,6 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu, > > guest_xive = spapr_ovec_test(ov5_guest, OV5_XIVE_EXPLOIT); > > - /* > - * HPT resizing is a bit of a special case, because when enabled > - * we assume an HPT guest will support it until it says it > - * doesn't, instead of assuming it won't support it until it says > - * it does. Strictly speaking that approach could break for > - * guests which don't make a CAS call, but those are so old we > - * don't care about them. Without that assumption we'd have to > - * make at least a temporary allocation of an HPT sized for max > - * memory, which could be impossibly difficult under KVM HV if > - * maxram is large. > - */ > - if (!guest_radix && !spapr_ovec_test(ov5_guest, OV5_HPT_RESIZE)) { > - int maxshift = spapr_hpt_shift_for_ramsize(MACHINE(spapr)->maxram_size); > - > - if (spapr->resize_hpt == SPAPR_RESIZE_HPT_REQUIRED) { > - error_report( > - "h_client_architecture_support: Guest doesn't support HPT resizing, but resize-hpt=required"); > - exit(1); > - } > - > - if (spapr->htab_shift < maxshift) { > - /* Guest doesn't know about HPT resizing, so we > - * pre-emptively resize for the maximum permitted RAM. At > - * the point this is called, nothing should have been > - * entered into the existing HPT */ > - spapr_reallocate_hpt(spapr, maxshift, &error_fatal); > - push_sregs_to_kvm_pr(spapr); > - } > - } > - > /* NOTE: there are actually a number of ov5 bits where input from the > * guest is always zero, and the platform/QEMU enables them independently > * of guest input. To model these properly we'd want some sort of mask, > @@ -1806,6 +1777,12 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu, > error_report("Guest requested unavailable MMU mode (hash)."); > exit(EXIT_FAILURE); > } > + if (spapr->resize_hpt == SPAPR_RESIZE_HPT_REQUIRED && > + !spapr_ovec_test(ov5_guest, OV5_HPT_RESIZE)) { > + error_report( > + "h_client_architecture_support: Guest doesn't support HPT resizing, but resize-hpt=required"); > + exit(1); > + } > } > spapr->cas_pre_isa3_guest = !spapr_ovec_test(ov1_guest, OV1_PPC_3_00); > spapr_ovec_cleanup(ov1_guest); > @@ -1838,11 +1815,23 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu, > void *fdt; > SpaprDeviceTreeUpdateHeader hdr = { .version_id = 1 }; > > - /* If spapr_machine_reset() did not set up a HPT but one is necessary > - * (because the guest isn't going to use radix) then set it up here. */ > - if ((spapr->patb_entry & PATE1_GR) && !guest_radix) { > - /* legacy hash or new hash: */ > - spapr_setup_hpt_and_vrma(spapr); > + if (!guest_radix) { > + /* > + * Either spapr_machine_reset() did not set up a HPT but one > + * is necessary (because the guest isn't going to use radix), > + * or the guest doesn't know about HPT resizing and we need to > + * pre-emptively resize for the maximum permitted RAM. Set it > + * up here. At the point this is called, nothing should have > + * been entered into the existing HPT. > + */ > + if (spapr->patb_entry & PATE1_GR || spapr->htab_shift < maxshift) { > + /* legacy hash or new hash: */ > + spapr_setup_hpt_and_vrma(spapr); > + push_sregs_to_kvm_pr(spapr); > + } > + } else { > + spapr_free_hpt(spapr); > + spapr_reset_patb_entry(spapr); > } > > if (fdt_bufsize < sizeof(hdr)) { > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > index 09110961a589..9d88b5596481 100644 > --- a/include/hw/ppc/spapr.h > +++ b/include/hw/ppc/spapr.h > @@ -919,4 +919,5 @@ void spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize, > > void spapr_set_all_lpcrs(target_ulong value, target_ulong mask); > hwaddr spapr_get_rtas_addr(void); > +void spapr_reset_patb_entry(SpaprMachineState *spapr); > #endif /* HW_SPAPR_H */ > -- 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