| Message ID | 20220216063903.1782281-2-npiggin@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/3] target/ppc: Fix POWER9 DD2.0 PVR, add DD2.1 | expand |
On Wed, Feb 16, 2022 at 04:39:02PM +1000, Nicholas Piggin wrote: > The behaviour of the Address Translation Mode on Interrupt resource is > not consistently supported by all CPU versions or all KVM versions: > KVM-HV does not support mode 2, and does not support mode 3 on POWER7 or > early POWER9 processesors. KVM PR only supports mode 0. TCG supports all > modes (0, 2, 3). This leads to inconsistencies in guest behaviour and > could cause problems migrating guests. > > This was not noticable for Linux guests for a long time because the > kernel only uses modes 0 and 3, and it used to consider AIL-3 to be > advisory in that it would always keep the AIL-0 vectors around. Recent > Linux guests depend on the AIL mode working as specified in order to > support the SCV facility interrupt. If AIL-3 can not be provided, then > Linux must be given an error so it can disable the SCV facility, rather > than silently failing. > > Add the ail-mode-3 capability to specify that AIL-3 is supported. AIL-0 > is implied as the baseline, and AIL-2 is no longer supported by spapr. > AIL-2 is not known to be used by any software, but support in TCG could > be restored with an ail-mode-2 capability quite easily if a regression > is reported. > > Modify the H_SET_MODE Address Translation Mode on Interrupt resource > handler to check capabilities and correctly return error if not > supported. > > A heuristic is added for KVM to determine AIL-3 support before the > introduction of a new KVM CAP, because blanket disabling AIL-3 has too > much performance cost. > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> [snip] > diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c > index dc93b99189..1338c41f8f 100644 > --- a/target/ppc/kvm.c > +++ b/target/ppc/kvm.c > @@ -2563,6 +2563,35 @@ int kvmppc_has_cap_rpt_invalidate(void) > return cap_rpt_invalidate; > } > > +bool kvmppc_supports_ail_3(void) > +{ > + PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class(); > + > + /* > + * KVM PR only supports AIL-0 > + */ > + if (kvmppc_is_pr(kvm_state)) { > + return 0; > + } > + > + /* > + * KVM HV hosts support AIL-3 on POWER8 and above, except for radix > + * mode on some early POWER9s. > + */ > + if (!(pcc->insns_flags2 & PPC2_ISA207S)) { > + return 0; > + } > + > + /* These tests match the CPU_FTR_P9_RADIX_PREFETCH_BUG flag in Linux */ > + if (((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD1) || > + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD20) || > + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD21)) { > + return 0; > + } Deducing what KVM supports rather than getting it to tell us explicitly with a cap is usually frowned upon. However, given the earlier discussion, I'm satisfied that this is the least bad available option, at least for now. > + > + return 1; > +} > + > PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void) > { > uint32_t host_pvr = mfpvr(); > diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h > index ee9325bf9a..7bba26d1da 100644 > --- a/target/ppc/kvm_ppc.h > +++ b/target/ppc/kvm_ppc.h > @@ -73,6 +73,7 @@ int kvmppc_set_cap_nested_kvm_hv(int enable); > int kvmppc_get_cap_large_decr(void); > int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable); > int kvmppc_has_cap_rpt_invalidate(void); > +bool kvmppc_supports_ail_3(void); > int kvmppc_enable_hwrng(void); > int kvmppc_put_books_sregs(PowerPCCPU *cpu); > PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void); > @@ -393,6 +394,11 @@ static inline int kvmppc_has_cap_rpt_invalidate(void) > return false; > } > > +static inline bool kvmppc_supports_ail_3(void) > +{ > + return false; > +} > + > static inline int kvmppc_enable_hwrng(void) > { > return -1;
Excerpts from David Gibson's message of February 17, 2022 10:17 am: > On Wed, Feb 16, 2022 at 04:39:02PM +1000, Nicholas Piggin wrote: >> The behaviour of the Address Translation Mode on Interrupt resource is >> not consistently supported by all CPU versions or all KVM versions: >> KVM-HV does not support mode 2, and does not support mode 3 on POWER7 or >> early POWER9 processesors. KVM PR only supports mode 0. TCG supports all >> modes (0, 2, 3). This leads to inconsistencies in guest behaviour and >> could cause problems migrating guests. >> >> This was not noticable for Linux guests for a long time because the >> kernel only uses modes 0 and 3, and it used to consider AIL-3 to be >> advisory in that it would always keep the AIL-0 vectors around. Recent >> Linux guests depend on the AIL mode working as specified in order to >> support the SCV facility interrupt. If AIL-3 can not be provided, then >> Linux must be given an error so it can disable the SCV facility, rather >> than silently failing. >> >> Add the ail-mode-3 capability to specify that AIL-3 is supported. AIL-0 >> is implied as the baseline, and AIL-2 is no longer supported by spapr. >> AIL-2 is not known to be used by any software, but support in TCG could >> be restored with an ail-mode-2 capability quite easily if a regression >> is reported. >> >> Modify the H_SET_MODE Address Translation Mode on Interrupt resource >> handler to check capabilities and correctly return error if not >> supported. >> >> A heuristic is added for KVM to determine AIL-3 support before the >> introduction of a new KVM CAP, because blanket disabling AIL-3 has too >> much performance cost. >> >> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > > Reviewed-by: David Gibson <david@gibson.dropbear.id.au> > > [snip] >> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c >> index dc93b99189..1338c41f8f 100644 >> --- a/target/ppc/kvm.c >> +++ b/target/ppc/kvm.c >> @@ -2563,6 +2563,35 @@ int kvmppc_has_cap_rpt_invalidate(void) >> return cap_rpt_invalidate; >> } >> >> +bool kvmppc_supports_ail_3(void) >> +{ >> + PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class(); >> + >> + /* >> + * KVM PR only supports AIL-0 >> + */ >> + if (kvmppc_is_pr(kvm_state)) { >> + return 0; >> + } >> + >> + /* >> + * KVM HV hosts support AIL-3 on POWER8 and above, except for radix >> + * mode on some early POWER9s. >> + */ >> + if (!(pcc->insns_flags2 & PPC2_ISA207S)) { >> + return 0; >> + } >> + >> + /* These tests match the CPU_FTR_P9_RADIX_PREFETCH_BUG flag in Linux */ >> + if (((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD1) || >> + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD20) || >> + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD21)) { >> + return 0; >> + } > > Deducing what KVM supports rather than getting it to tell us > explicitly with a cap is usually frowned upon. However, given the > earlier discussion, I'm satisfied that this is the least bad available > option, at least for now. BTW this particular test doesn't work as I hoped because we only have a power9 dd2.0 model. Adding a 2.2 or 2.3 would be possible. Maybe overkill. I'll change the test just to catch all POWER9 for now. KVM cap has been allocated in the upstream kvm tree now though, so I'll re-send soon. Thanks, Nick
On Wed, Feb 23, 2022 at 05:42:06PM +1000, Nicholas Piggin wrote: > Excerpts from David Gibson's message of February 17, 2022 10:17 am: > > On Wed, Feb 16, 2022 at 04:39:02PM +1000, Nicholas Piggin wrote: > >> The behaviour of the Address Translation Mode on Interrupt resource is > >> not consistently supported by all CPU versions or all KVM versions: > >> KVM-HV does not support mode 2, and does not support mode 3 on POWER7 or > >> early POWER9 processesors. KVM PR only supports mode 0. TCG supports all > >> modes (0, 2, 3). This leads to inconsistencies in guest behaviour and > >> could cause problems migrating guests. > >> > >> This was not noticable for Linux guests for a long time because the > >> kernel only uses modes 0 and 3, and it used to consider AIL-3 to be > >> advisory in that it would always keep the AIL-0 vectors around. Recent > >> Linux guests depend on the AIL mode working as specified in order to > >> support the SCV facility interrupt. If AIL-3 can not be provided, then > >> Linux must be given an error so it can disable the SCV facility, rather > >> than silently failing. > >> > >> Add the ail-mode-3 capability to specify that AIL-3 is supported. AIL-0 > >> is implied as the baseline, and AIL-2 is no longer supported by spapr. > >> AIL-2 is not known to be used by any software, but support in TCG could > >> be restored with an ail-mode-2 capability quite easily if a regression > >> is reported. > >> > >> Modify the H_SET_MODE Address Translation Mode on Interrupt resource > >> handler to check capabilities and correctly return error if not > >> supported. > >> > >> A heuristic is added for KVM to determine AIL-3 support before the > >> introduction of a new KVM CAP, because blanket disabling AIL-3 has too > >> much performance cost. > >> > >> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > > > > Reviewed-by: David Gibson <david@gibson.dropbear.id.au> > > > > [snip] > >> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c > >> index dc93b99189..1338c41f8f 100644 > >> --- a/target/ppc/kvm.c > >> +++ b/target/ppc/kvm.c > >> @@ -2563,6 +2563,35 @@ int kvmppc_has_cap_rpt_invalidate(void) > >> return cap_rpt_invalidate; > >> } > >> > >> +bool kvmppc_supports_ail_3(void) > >> +{ > >> + PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class(); > >> + > >> + /* > >> + * KVM PR only supports AIL-0 > >> + */ > >> + if (kvmppc_is_pr(kvm_state)) { > >> + return 0; > >> + } > >> + > >> + /* > >> + * KVM HV hosts support AIL-3 on POWER8 and above, except for radix > >> + * mode on some early POWER9s. > >> + */ > >> + if (!(pcc->insns_flags2 & PPC2_ISA207S)) { > >> + return 0; > >> + } > >> + > >> + /* These tests match the CPU_FTR_P9_RADIX_PREFETCH_BUG flag in Linux */ > >> + if (((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD1) || > >> + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD20) || > >> + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD21)) { > >> + return 0; > >> + } > > > > Deducing what KVM supports rather than getting it to tell us > > explicitly with a cap is usually frowned upon. However, given the > > earlier discussion, I'm satisfied that this is the least bad available > > option, at least for now. > > BTW this particular test doesn't work as I hoped because we only have > a power9 dd2.0 model. Oh.. yes... IIRC dd2.0 is barely present in the wild, since it doesn't have vital Spectre mitigations.... > Adding a 2.2 or 2.3 would be possible. Maybe overkill. I'll change > the test just to catch all POWER9 for now. ... no, given the above, I think we should definitely add the newer models. Maybe even remove dd2.0 and replace it with the newer ones. > KVM cap has been allocated in the upstream kvm tree now though, so I'll > re-send soon. > > Thanks, > Nick >
>>>> + /* These tests match the CPU_FTR_P9_RADIX_PREFETCH_BUG flag in Linux */ >>>> + if (((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD1) || >>>> + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD20) || >>>> + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD21)) { >>>> + return 0; >>>> + } >>> >>> Deducing what KVM supports rather than getting it to tell us >>> explicitly with a cap is usually frowned upon. However, given the >>> earlier discussion, I'm satisfied that this is the least bad available >>> option, at least for now. >> >> BTW this particular test doesn't work as I hoped because we only have >> a power9 dd2.0 model. > > Oh.. yes... IIRC dd2.0 is barely present in the wild, since it doesn't > have vital Spectre mitigations.... > >> Adding a 2.2 or 2.3 would be possible. Maybe overkill. I'll change >> the test just to catch all POWER9 for now. > > ... no, given the above, I think we should definitely add the newer > models. Maybe even remove dd2.0 and replace it with the newer ones. yes. It's really not a big effort. Thanks, C.
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 3d6ec309dd..fd7eccbdfd 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -4606,6 +4606,11 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data) 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; + + /* This cap specifies whether the AIL 3 mode for H_SET_RESOURCE is + * supported. The default is modified by default_caps_with_cpu(). + */ + smc->default_caps.caps[SPAPR_CAP_AIL_MODE_3] = SPAPR_CAP_ON; spapr_caps_add_properties(smc); smc->irq = &spapr_irq_dual; smc->dr_phb_enabled = true; diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c index ed7c077a0d..e2412aaa57 100644 --- a/hw/ppc/spapr_caps.c +++ b/hw/ppc/spapr_caps.c @@ -613,6 +613,33 @@ static void cap_rpt_invalidate_apply(SpaprMachineState *spapr, } } +static void cap_ail_mode_3_apply(SpaprMachineState *spapr, + uint8_t val, Error **errp) +{ + ERRP_GUARD(); + PowerPCCPU *cpu = POWERPC_CPU(first_cpu); + PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu); + + if (!val) { + return; + } + + if (tcg_enabled()) { + /* AIL-3 is only supported on POWER8 and above CPUs. */ + if (!(pcc->insns_flags2 & PPC2_ISA207S)) { + error_setg(errp, "TCG only supports cap-ail-mode-3 on POWER8 and later CPUs"); + error_append_hint(errp, "Try appending -machine cap-ail-mode-3=off\n"); + return; + } + } else if (kvm_enabled()) { + if (!kvmppc_supports_ail_3()) { + error_setg(errp, "KVM implementation does not support cap-ail-mode-3"); + error_append_hint(errp, "Try appending -machine cap-ail-mode-3=off\n"); + return; + } + } +} + SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = { [SPAPR_CAP_HTM] = { .name = "htm", @@ -730,6 +757,15 @@ SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = { .type = "bool", .apply = cap_rpt_invalidate_apply, }, + [SPAPR_CAP_AIL_MODE_3] = { + .name = "ail-mode-3", + .description = "Alternate Interrupt Location (AIL) mode 3 support", + .index = SPAPR_CAP_AIL_MODE_3, + .get = spapr_cap_get_bool, + .set = spapr_cap_set_bool, + .type = "bool", + .apply = cap_ail_mode_3_apply, + }, }; static SpaprCapabilities default_caps_with_cpu(SpaprMachineState *spapr, @@ -749,6 +785,7 @@ static SpaprCapabilities default_caps_with_cpu(SpaprMachineState *spapr, 0, spapr->max_compat_pvr)) { caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_OFF; caps.caps[SPAPR_CAP_CFPC] = SPAPR_CAP_BROKEN; + caps.caps[SPAPR_CAP_AIL_MODE_3] = SPAPR_CAP_OFF; } if (!ppc_type_check_compat(cputype, CPU_POWERPC_LOGICAL_2_06_PLUS, diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c index 222c1b6bbd..fa60505315 100644 --- a/hw/ppc/spapr_hcall.c +++ b/hw/ppc/spapr_hcall.c @@ -811,30 +811,32 @@ static target_ulong h_set_mode_resource_le(PowerPCCPU *cpu, } static target_ulong h_set_mode_resource_addr_trans_mode(PowerPCCPU *cpu, + SpaprMachineState *spapr, target_ulong mflags, target_ulong value1, target_ulong value2) { - PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu); - - if (!(pcc->insns_flags2 & PPC2_ISA207S)) { - return H_P2; - } if (value1) { return H_P3; } + if (value2) { return H_P4; } - if (mflags == 1) { - /* AIL=1 is reserved in POWER8/POWER9/POWER10 */ + /* + * AIL-1 is not architected, and AIL-2 is not supported by QEMU spapr. + * It is supported for faithful emulation of bare metal systems, but for + * compatibility concerns we leave it out of the pseries machine. + */ + if (mflags != 0 && mflags != 3) { return H_UNSUPPORTED_FLAG; } - if (mflags == 2 && (pcc->insns_flags2 & PPC2_ISA310)) { - /* AIL=2 is reserved in POWER10 (ISA v3.1) */ - return H_UNSUPPORTED_FLAG; + if (mflags == 3) { + if (!spapr_get_cap(spapr, SPAPR_CAP_AIL_MODE_3)) { + return H_UNSUPPORTED_FLAG; + } } spapr_set_all_lpcrs(mflags << LPCR_AIL_SHIFT, LPCR_AIL); @@ -853,7 +855,7 @@ static target_ulong h_set_mode(PowerPCCPU *cpu, SpaprMachineState *spapr, ret = h_set_mode_resource_le(cpu, spapr, args[0], args[2], args[3]); break; case H_SET_MODE_RESOURCE_ADDR_TRANS_MODE: - ret = h_set_mode_resource_addr_trans_mode(cpu, args[0], + ret = h_set_mode_resource_addr_trans_mode(cpu, spapr, args[0], args[2], args[3]); break; } diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h index ee7504b976..edbf3eeed0 100644 --- a/include/hw/ppc/spapr.h +++ b/include/hw/ppc/spapr.h @@ -77,8 +77,10 @@ typedef enum { #define SPAPR_CAP_FWNMI 0x0A /* Support H_RPT_INVALIDATE */ #define SPAPR_CAP_RPT_INVALIDATE 0x0B +/* Support for AIL modes */ +#define SPAPR_CAP_AIL_MODE_3 0x0C /* Num Caps */ -#define SPAPR_CAP_NUM (SPAPR_CAP_RPT_INVALIDATE + 1) +#define SPAPR_CAP_NUM (SPAPR_CAP_AIL_MODE_3 + 1) /* * Capability Values diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c index dc93b99189..1338c41f8f 100644 --- a/target/ppc/kvm.c +++ b/target/ppc/kvm.c @@ -2563,6 +2563,35 @@ int kvmppc_has_cap_rpt_invalidate(void) return cap_rpt_invalidate; } +bool kvmppc_supports_ail_3(void) +{ + PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class(); + + /* + * KVM PR only supports AIL-0 + */ + if (kvmppc_is_pr(kvm_state)) { + return 0; + } + + /* + * KVM HV hosts support AIL-3 on POWER8 and above, except for radix + * mode on some early POWER9s. + */ + if (!(pcc->insns_flags2 & PPC2_ISA207S)) { + return 0; + } + + /* These tests match the CPU_FTR_P9_RADIX_PREFETCH_BUG flag in Linux */ + if (((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD1) || + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD20) || + ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD21)) { + return 0; + } + + return 1; +} + PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void) { uint32_t host_pvr = mfpvr(); diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h index ee9325bf9a..7bba26d1da 100644 --- a/target/ppc/kvm_ppc.h +++ b/target/ppc/kvm_ppc.h @@ -73,6 +73,7 @@ int kvmppc_set_cap_nested_kvm_hv(int enable); int kvmppc_get_cap_large_decr(void); int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable); int kvmppc_has_cap_rpt_invalidate(void); +bool kvmppc_supports_ail_3(void); int kvmppc_enable_hwrng(void); int kvmppc_put_books_sregs(PowerPCCPU *cpu); PowerPCCPUClass *kvm_ppc_get_host_cpu_class(void); @@ -393,6 +394,11 @@ static inline int kvmppc_has_cap_rpt_invalidate(void) return false; } +static inline bool kvmppc_supports_ail_3(void) +{ + return false; +} + static inline int kvmppc_enable_hwrng(void) { return -1;
The behaviour of the Address Translation Mode on Interrupt resource is not consistently supported by all CPU versions or all KVM versions: KVM-HV does not support mode 2, and does not support mode 3 on POWER7 or early POWER9 processesors. KVM PR only supports mode 0. TCG supports all modes (0, 2, 3). This leads to inconsistencies in guest behaviour and could cause problems migrating guests. This was not noticable for Linux guests for a long time because the kernel only uses modes 0 and 3, and it used to consider AIL-3 to be advisory in that it would always keep the AIL-0 vectors around. Recent Linux guests depend on the AIL mode working as specified in order to support the SCV facility interrupt. If AIL-3 can not be provided, then Linux must be given an error so it can disable the SCV facility, rather than silently failing. Add the ail-mode-3 capability to specify that AIL-3 is supported. AIL-0 is implied as the baseline, and AIL-2 is no longer supported by spapr. AIL-2 is not known to be used by any software, but support in TCG could be restored with an ail-mode-2 capability quite easily if a regression is reported. Modify the H_SET_MODE Address Translation Mode on Interrupt resource handler to check capabilities and correctly return error if not supported. A heuristic is added for KVM to determine AIL-3 support before the introduction of a new KVM CAP, because blanket disabling AIL-3 has too much performance cost. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- Since v1: - Minor cleanups. - Improve KVM tests to catch the problem POWER9s. - Use default_caps_with_cpu() to clear the cap for POWER7 hw/ppc/spapr.c | 5 +++++ hw/ppc/spapr_caps.c | 37 +++++++++++++++++++++++++++++++++++++ hw/ppc/spapr_hcall.c | 24 +++++++++++++----------- include/hw/ppc/spapr.h | 4 +++- target/ppc/kvm.c | 29 +++++++++++++++++++++++++++++ target/ppc/kvm_ppc.h | 6 ++++++ 6 files changed, 93 insertions(+), 12 deletions(-)