| Message ID | 20240122-arm64-2023-dpisa-v4-3-776e094861df@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: Support for 2023 DPISA extensions | expand |
On Mon, 22 Jan 2024 16:28:06 +0000, Mark Brown <broonie@kernel.org> wrote: > > FEAT_FPMR defines a new EL0 accessible register FPMR use to configure the > FP8 related features added to the architecture at the same time. Detect > support for this register and context switch it for EL0 when present. > > Due to the sharing of responsibility for saving floating point state > between the host kernel and KVM FP8 support is not yet implemented in KVM > and a stub similar to that used for SVCR is provided for FPMR in order to > avoid bisection issues. To make it easier to share host state with the > hypervisor we store FPMR as a hardened usercopy field in uw (along with > some padding). > > Signed-off-by: Mark Brown <broonie@kernel.org> > --- > arch/arm64/include/asm/cpufeature.h | 5 +++++ > arch/arm64/include/asm/fpsimd.h | 2 ++ > arch/arm64/include/asm/kvm_host.h | 1 + > arch/arm64/include/asm/processor.h | 4 ++++ > arch/arm64/kernel/cpufeature.c | 9 +++++++++ > arch/arm64/kernel/fpsimd.c | 13 +++++++++++++ > arch/arm64/kvm/fpsimd.c | 1 + > arch/arm64/tools/cpucaps | 1 + > 8 files changed, 36 insertions(+) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 21c824edf8ce..34fcdbc65d7d 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -768,6 +768,11 @@ static __always_inline bool system_supports_tpidr2(void) > return system_supports_sme(); > } > > +static __always_inline bool system_supports_fpmr(void) > +{ > + return alternative_has_cap_unlikely(ARM64_HAS_FPMR); > +} > + > static __always_inline bool system_supports_cnp(void) > { > return alternative_has_cap_unlikely(ARM64_HAS_CNP); > diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h > index 50e5f25d3024..6cf72b0d2c04 100644 > --- a/arch/arm64/include/asm/fpsimd.h > +++ b/arch/arm64/include/asm/fpsimd.h > @@ -89,6 +89,7 @@ struct cpu_fp_state { > void *sve_state; > void *sme_state; > u64 *svcr; > + unsigned long *fpmr; > unsigned int sve_vl; > unsigned int sme_vl; > enum fp_type *fp_type; > @@ -154,6 +155,7 @@ extern void cpu_enable_sve(const struct arm64_cpu_capabilities *__unused); > extern void cpu_enable_sme(const struct arm64_cpu_capabilities *__unused); > extern void cpu_enable_sme2(const struct arm64_cpu_capabilities *__unused); > extern void cpu_enable_fa64(const struct arm64_cpu_capabilities *__unused); > +extern void cpu_enable_fpmr(const struct arm64_cpu_capabilities *__unused); > > extern u64 read_smcr_features(void); > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 21c57b812569..7993694a54af 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -543,6 +543,7 @@ struct kvm_vcpu_arch { > enum fp_type fp_type; > unsigned int sve_max_vl; > u64 svcr; > + unsigned long fpmr; As this directly represents a register, I'd rather you use a type that represents the size of that register unambiguously (u64). > > /* Stage 2 paging state used by the hardware on next switch */ > struct kvm_s2_mmu *hw_mmu; > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index 5b0a04810b23..b453c66d3fae 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -155,6 +155,8 @@ struct thread_struct { > struct { > unsigned long tp_value; /* TLS register */ > unsigned long tp2_value; > + unsigned long fpmr; > + unsigned long pad; > struct user_fpsimd_state fpsimd_state; > } uw; > > @@ -253,6 +255,8 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset, > BUILD_BUG_ON(sizeof_field(struct thread_struct, uw) != > sizeof_field(struct thread_struct, uw.tp_value) + > sizeof_field(struct thread_struct, uw.tp2_value) + > + sizeof_field(struct thread_struct, uw.fpmr) + > + sizeof_field(struct thread_struct, uw.pad) + > sizeof_field(struct thread_struct, uw.fpsimd_state)); > > *offset = offsetof(struct thread_struct, uw); > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index eae59ec0f4b0..0263565f617a 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -272,6 +272,7 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = { > }; > > static const struct arm64_ftr_bits ftr_id_aa64pfr2[] = { > + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_FPMR_SHIFT, 4, 0), > ARM64_FTR_END, > }; > > @@ -2767,6 +2768,14 @@ static const struct arm64_cpu_capabilities arm64_features[] = { > .type = ARM64_CPUCAP_SYSTEM_FEATURE, > .matches = has_lpa2, > }, > + { > + .desc = "FPMR", > + .type = ARM64_CPUCAP_SYSTEM_FEATURE, > + .capability = ARM64_HAS_FPMR, > + .matches = has_cpuid_feature, > + .cpu_enable = cpu_enable_fpmr, > + ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, FPMR, IMP) > + }, > {}, > }; > > diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c > index a5dc6f764195..8e24b5e5e192 100644 > --- a/arch/arm64/kernel/fpsimd.c > +++ b/arch/arm64/kernel/fpsimd.c > @@ -359,6 +359,9 @@ static void task_fpsimd_load(void) > WARN_ON(preemptible()); > WARN_ON(test_thread_flag(TIF_KERNEL_FPSTATE)); > > + if (system_supports_fpmr()) > + write_sysreg_s(current->thread.uw.fpmr, SYS_FPMR); > + > if (system_supports_sve() || system_supports_sme()) { > switch (current->thread.fp_type) { > case FP_STATE_FPSIMD: > @@ -446,6 +449,9 @@ static void fpsimd_save_user_state(void) > if (test_thread_flag(TIF_FOREIGN_FPSTATE)) > return; > > + if (system_supports_fpmr()) > + *(last->fpmr) = read_sysreg_s(SYS_FPMR); > + > /* > * If a task is in a syscall the ABI allows us to only > * preserve the state shared with FPSIMD so don't bother > @@ -688,6 +694,12 @@ static void sve_to_fpsimd(struct task_struct *task) > } > } > > +void cpu_enable_fpmr(const struct arm64_cpu_capabilities *__always_unused p) > +{ > + write_sysreg_s(read_sysreg_s(SYS_SCTLR_EL1) | SCTLR_EL1_EnFPM_MASK, > + SYS_SCTLR_EL1); > +} > + > #ifdef CONFIG_ARM64_SVE > /* > * Call __sve_free() directly only if you know task can't be scheduled > @@ -1680,6 +1692,7 @@ static void fpsimd_bind_task_to_cpu(void) > last->sve_vl = task_get_sve_vl(current); > last->sme_vl = task_get_sme_vl(current); > last->svcr = ¤t->thread.svcr; > + last->fpmr = ¤t->thread.uw.fpmr; > last->fp_type = ¤t->thread.fp_type; > last->to_save = FP_STATE_CURRENT; > current->thread.fpsimd_cpu = smp_processor_id(); > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c > index 8c1d0d4853df..e3e611e30e91 100644 > --- a/arch/arm64/kvm/fpsimd.c > +++ b/arch/arm64/kvm/fpsimd.c > @@ -153,6 +153,7 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) > fp_state.sve_vl = vcpu->arch.sve_max_vl; > fp_state.sme_state = NULL; > fp_state.svcr = &vcpu->arch.svcr; > + fp_state.fpmr = &vcpu->arch.fpmr; > fp_state.fp_type = &vcpu->arch.fp_type; Given the number of fields you keep track of, it would make a lot more sense if these FP-related fields were in their own little structure and tracked by a single pointer (I don't think there is a case where we track them independently). Thanks, M.
On Fri, Feb 23, 2024 at 11:07:02AM +0000, Marc Zyngier wrote: > Mark Brown <broonie@kernel.org> wrote: > > --- a/arch/arm64/kvm/fpsimd.c > > +++ b/arch/arm64/kvm/fpsimd.c > > @@ -153,6 +153,7 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) > > fp_state.sve_vl = vcpu->arch.sve_max_vl; > > fp_state.sme_state = NULL; > > fp_state.svcr = &vcpu->arch.svcr; > > + fp_state.fpmr = &vcpu->arch.fpmr; > > fp_state.fp_type = &vcpu->arch.fp_type; > Given the number of fields you keep track of, it would make a lot more > sense if these FP-related fields were in their own little structure > and tracked by a single pointer (I don't think there is a case where > we track them independently). I sent a patch series that attempted to address this somewhat by refactoring things so that we initialise the struct we bind during vCPU setup rather than each time we prepare to switch away from the guest: https://lore.kernel.org/linux-arm-kernel/20240226-kvm-arm64-group-fp-data-v1-0-07d13759517e@kernel.org/ which you weren't terribly enthusiastic about: https://lore.kernel.org/all/86y1b027mc.wl-maz@kernel.org/ As covered in the changelog for patch 2 of that series the FP state includes both system registers which KVM wants to expose via it's system register ABI and FPSIMD state which the host kernel wants to flag as suitable for hardended usercopy by embedding in thread_struct.uw. This means that pulling everything into a single structure which is used throughout the kernel would require a bunch of surgery which I'm not sure is worth the effort or ongoing maintainance cost. The current approach is verbose but not complicated and localised to the code managing the FP state, as I said in the discussion on that thread I think it represents a reasonable tradeoff.
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 21c824edf8ce..34fcdbc65d7d 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -768,6 +768,11 @@ static __always_inline bool system_supports_tpidr2(void) return system_supports_sme(); } +static __always_inline bool system_supports_fpmr(void) +{ + return alternative_has_cap_unlikely(ARM64_HAS_FPMR); +} + static __always_inline bool system_supports_cnp(void) { return alternative_has_cap_unlikely(ARM64_HAS_CNP); diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index 50e5f25d3024..6cf72b0d2c04 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -89,6 +89,7 @@ struct cpu_fp_state { void *sve_state; void *sme_state; u64 *svcr; + unsigned long *fpmr; unsigned int sve_vl; unsigned int sme_vl; enum fp_type *fp_type; @@ -154,6 +155,7 @@ extern void cpu_enable_sve(const struct arm64_cpu_capabilities *__unused); extern void cpu_enable_sme(const struct arm64_cpu_capabilities *__unused); extern void cpu_enable_sme2(const struct arm64_cpu_capabilities *__unused); extern void cpu_enable_fa64(const struct arm64_cpu_capabilities *__unused); +extern void cpu_enable_fpmr(const struct arm64_cpu_capabilities *__unused); extern u64 read_smcr_features(void); diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 21c57b812569..7993694a54af 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -543,6 +543,7 @@ struct kvm_vcpu_arch { enum fp_type fp_type; unsigned int sve_max_vl; u64 svcr; + unsigned long fpmr; /* Stage 2 paging state used by the hardware on next switch */ struct kvm_s2_mmu *hw_mmu; diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 5b0a04810b23..b453c66d3fae 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -155,6 +155,8 @@ struct thread_struct { struct { unsigned long tp_value; /* TLS register */ unsigned long tp2_value; + unsigned long fpmr; + unsigned long pad; struct user_fpsimd_state fpsimd_state; } uw; @@ -253,6 +255,8 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset, BUILD_BUG_ON(sizeof_field(struct thread_struct, uw) != sizeof_field(struct thread_struct, uw.tp_value) + sizeof_field(struct thread_struct, uw.tp2_value) + + sizeof_field(struct thread_struct, uw.fpmr) + + sizeof_field(struct thread_struct, uw.pad) + sizeof_field(struct thread_struct, uw.fpsimd_state)); *offset = offsetof(struct thread_struct, uw); diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index eae59ec0f4b0..0263565f617a 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -272,6 +272,7 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = { }; static const struct arm64_ftr_bits ftr_id_aa64pfr2[] = { + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_FPMR_SHIFT, 4, 0), ARM64_FTR_END, }; @@ -2767,6 +2768,14 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .type = ARM64_CPUCAP_SYSTEM_FEATURE, .matches = has_lpa2, }, + { + .desc = "FPMR", + .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .capability = ARM64_HAS_FPMR, + .matches = has_cpuid_feature, + .cpu_enable = cpu_enable_fpmr, + ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, FPMR, IMP) + }, {}, }; diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index a5dc6f764195..8e24b5e5e192 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -359,6 +359,9 @@ static void task_fpsimd_load(void) WARN_ON(preemptible()); WARN_ON(test_thread_flag(TIF_KERNEL_FPSTATE)); + if (system_supports_fpmr()) + write_sysreg_s(current->thread.uw.fpmr, SYS_FPMR); + if (system_supports_sve() || system_supports_sme()) { switch (current->thread.fp_type) { case FP_STATE_FPSIMD: @@ -446,6 +449,9 @@ static void fpsimd_save_user_state(void) if (test_thread_flag(TIF_FOREIGN_FPSTATE)) return; + if (system_supports_fpmr()) + *(last->fpmr) = read_sysreg_s(SYS_FPMR); + /* * If a task is in a syscall the ABI allows us to only * preserve the state shared with FPSIMD so don't bother @@ -688,6 +694,12 @@ static void sve_to_fpsimd(struct task_struct *task) } } +void cpu_enable_fpmr(const struct arm64_cpu_capabilities *__always_unused p) +{ + write_sysreg_s(read_sysreg_s(SYS_SCTLR_EL1) | SCTLR_EL1_EnFPM_MASK, + SYS_SCTLR_EL1); +} + #ifdef CONFIG_ARM64_SVE /* * Call __sve_free() directly only if you know task can't be scheduled @@ -1680,6 +1692,7 @@ static void fpsimd_bind_task_to_cpu(void) last->sve_vl = task_get_sve_vl(current); last->sme_vl = task_get_sme_vl(current); last->svcr = ¤t->thread.svcr; + last->fpmr = ¤t->thread.uw.fpmr; last->fp_type = ¤t->thread.fp_type; last->to_save = FP_STATE_CURRENT; current->thread.fpsimd_cpu = smp_processor_id(); diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 8c1d0d4853df..e3e611e30e91 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -153,6 +153,7 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu) fp_state.sve_vl = vcpu->arch.sve_max_vl; fp_state.sme_state = NULL; fp_state.svcr = &vcpu->arch.svcr; + fp_state.fpmr = &vcpu->arch.fpmr; fp_state.fp_type = &vcpu->arch.fp_type; if (vcpu_has_sve(vcpu)) diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps index b912b1409fc0..63283550c8e8 100644 --- a/arch/arm64/tools/cpucaps +++ b/arch/arm64/tools/cpucaps @@ -26,6 +26,7 @@ HAS_ECV HAS_ECV_CNTPOFF HAS_EPAN HAS_EVT +HAS_FPMR HAS_FGT HAS_FPSIMD HAS_GENERIC_AUTH
FEAT_FPMR defines a new EL0 accessible register FPMR use to configure the FP8 related features added to the architecture at the same time. Detect support for this register and context switch it for EL0 when present. Due to the sharing of responsibility for saving floating point state between the host kernel and KVM FP8 support is not yet implemented in KVM and a stub similar to that used for SVCR is provided for FPMR in order to avoid bisection issues. To make it easier to share host state with the hypervisor we store FPMR as a hardened usercopy field in uw (along with some padding). Signed-off-by: Mark Brown <broonie@kernel.org> --- arch/arm64/include/asm/cpufeature.h | 5 +++++ arch/arm64/include/asm/fpsimd.h | 2 ++ arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/include/asm/processor.h | 4 ++++ arch/arm64/kernel/cpufeature.c | 9 +++++++++ arch/arm64/kernel/fpsimd.c | 13 +++++++++++++ arch/arm64/kvm/fpsimd.c | 1 + arch/arm64/tools/cpucaps | 1 + 8 files changed, 36 insertions(+)