Re: [PATCH v2 01/17] riscv: cpufeature: Fix thead vector hwcap removal

Charlie Jenkins
2024-04-16T20:40:44Z

On Tue, Apr 16, 2024 at 04:03:20PM +0100, Conor Dooley wrote:
> On Mon, Apr 15, 2024 at 09:11:58PM -0700, Charlie Jenkins wrote:
> > The riscv_cpuinfo struct that contains mvendorid and marchid is not
> > populated until all harts are booted which happens after the DT parsing.
> > Use the vendorid/archid values from the DT if available or assume all
> > harts have the same values as the boot hart as a fallback.
> >
> > Fixes: d82f32202e0d ("RISC-V: Ignore V from the riscv,isa DT property on older T-Head CPUs")
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> > arch/riscv/include/asm/sbi.h | 2 ++
> > arch/riscv/kernel/cpu.c | 36 ++++++++++++++++++++++++++++++++----
> > arch/riscv/kernel/cpufeature.c | 12 ++++++++++--
> > 3 files changed, 44 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> > index 6e68f8dff76b..0fab508a65b3 100644
> > --- a/arch/riscv/include/asm/sbi.h
> > +++ b/arch/riscv/include/asm/sbi.h
> > @@ -370,6 +370,8 @@ static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) { return -1
> > static inline void sbi_init(void) {}
> > #endif /* CONFIG_RISCV_SBI */
> >
> > +unsigned long riscv_get_mvendorid(void);
> > +unsigned long riscv_get_marchid(void);
> > unsigned long riscv_cached_mvendorid(unsigned int cpu_id);
> > unsigned long riscv_cached_marchid(unsigned int cpu_id);
> > unsigned long riscv_cached_mimpid(unsigned int cpu_id);
> > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> > index d11d6320fb0d..8c8250b98752 100644
> > --- a/arch/riscv/kernel/cpu.c
> > +++ b/arch/riscv/kernel/cpu.c
> > @@ -139,6 +139,34 @@ int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid)
> > return -1;
> > }
> >
> > +unsigned long __init riscv_get_marchid(void)
> > +{
> > + struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
> > +
> > +#if IS_ENABLED(CONFIG_RISCV_SBI)
> > + ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
> > +#elif IS_ENABLED(CONFIG_RISCV_M_MODE)
> > + ci->marchid = csr_read(CSR_MARCHID);
> > +#else
> > + ci->marchid = 0;
> > +#endif
> > + return ci->marchid;
> > +}
> > +
> > +unsigned long __init riscv_get_mvendorid(void)
> > +{
> > + struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
> > +
> > +#if IS_ENABLED(CONFIG_RISCV_SBI)
> > + ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> > +#elif IS_ENABLED(CONFIG_RISCV_M_MODE)
> > + ci->mvendorid = csr_read(CSR_MVENDORID);
> > +#else
> > + ci->mvendorid = 0;
> > +#endif
> > + return ci->mvendorid;
> > +}
> > +
> > DEFINE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
> >
> > unsigned long riscv_cached_mvendorid(unsigned int cpu_id)
> > @@ -170,12 +198,12 @@ static int riscv_cpuinfo_starting(unsigned int cpu)
> > struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
> >
> > #if IS_ENABLED(CONFIG_RISCV_SBI)
> > - ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> > - ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
> > + ci->mvendorid = ci->mvendorid ? ci->mvendorid : sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> > + ci->marchid = ci->marchid ? ci->marchid : sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
>
> Can we please not have double ternary stuff? This is awful to grok :(
> Can you do
> if (!ci->m*id)
> sbi_spec_is_0_1() ? 0 : sbi_get_m*id();
> instead? I think that is much easier to understand.
> Otherwise,
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Sure, thanks!

- Charlie

>
> Cheers,
> Conor.
>
> > ci->mimpid = sbi_spec_is_0_1() ? 0 : sbi_get_mimpid();
> > #elif IS_ENABLED(CONFIG_RISCV_M_MODE)
> > - ci->mvendorid = csr_read(CSR_MVENDORID);
> > - ci->marchid = csr_read(CSR_MARCHID);
> > + ci->mvendorid = ci->mvendorid ? ci->mvendorid : csr_read(CSR_MVENDORID);
> > + ci->marchid = ci->marchid ? ci->marchid : csr_read(CSR_MARCHID);
> > ci->mimpid = csr_read(CSR_MIMPID);
> > #else
> > ci->mvendorid = 0;
> > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> > index 3ed2359eae35..c6e27b45e192 100644
> > --- a/arch/riscv/kernel/cpufeature.c
> > +++ b/arch/riscv/kernel/cpufeature.c
> > @@ -490,6 +490,8 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
> > struct acpi_table_header *rhct;
> > acpi_status status;
> > unsigned int cpu;
> > + u64 boot_vendorid;
> > + u64 boot_archid;
> >
> > if (!acpi_disabled) {
> > status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
> > @@ -497,6 +499,13 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
> > return;
> > }
> >
> > + /*
> > + * Naively assume that all harts have the same mvendorid/marchid as the
> > + * boot hart.
> > + */
> > + boot_vendorid = riscv_get_mvendorid();
> > + boot_archid = riscv_get_marchid();
> > +
> > for_each_possible_cpu(cpu) {
> > struct riscv_isainfo *isainfo = &hart_isa[cpu];
> > unsigned long this_hwcap = 0;
> > @@ -544,8 +553,7 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
> > * CPU cores with the ratified spec will contain non-zero
> > * marchid.
> > */
> > - if (acpi_disabled && riscv_cached_mvendorid(cpu) == THEAD_VENDOR_ID &&
> > - riscv_cached_marchid(cpu) == 0x0) {
> > + if (acpi_disabled && boot_vendorid == THEAD_VENDOR_ID && boot_archid == 0x0) {
> > this_hwcap &= ~isa2hwcap[RISCV_ISA_EXT_v];
> > clear_bit(RISCV_ISA_EXT_v, isainfo->isa);
> > }
> >
> > --
> > 2.44.0
> >