On Mon, Feb 14, 2022 at 3:22 PM Atish Kumar Patra <atishp@xxxxxxxxxxxx> wrote: > > On Mon, Feb 14, 2022 at 2:22 PM Heiko Stübner <heiko@xxxxxxxxx> wrote: > > > > Am Montag, 14. Februar 2022, 21:42:32 CET schrieb Atish Patra: > > > On Mon, Feb 14, 2022 at 12:24 PM Heiko Stübner <heiko@xxxxxxxxx> wrote: > > > > > > > > Am Montag, 14. Februar 2022, 21:14:13 CET schrieb Atish Patra: > > > > > On Mon, Feb 14, 2022 at 12:06 PM Heiko Stübner <heiko@xxxxxxxxx> wrote: > > > > > > > > > > > > Am Donnerstag, 10. Februar 2022, 22:40:16 CET schrieb Atish Patra: > > > > > > > Multi-letter extensions can be probed using exising > > > > > > > riscv_isa_extension_available API now. It doesn't support versioning > > > > > > > right now as there is no use case for it. > > > > > > > Individual extension specific implementation will be added during > > > > > > > each extension support. > > > > > > > > > > > > > > Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx> > > > > > > > > > > > > Tested-by: Heiko Stuebner <heiko@xxxxxxxxx> > > > > > > > > > > > > > > > > > > By the way, does a similar parsing exist for opensbi as well? > > > > > > Things like svpbmt as well as zicbom have CSR bits controlling how > > > > > > these functions should behave (enabling them, etc), so I guess > > > > > > opensbi also needs to parse the extensions from the ISA string? > > > > > > > > > > > > > > > > > > > > > > No. Currently, OpenSBI relies on the CSR read/write & trap method to > > > > > identify the extensions [1]. > > > > > > > > > > https://github.com/riscv-software-src/opensbi/blob/master/lib/sbi/sbi_hart.c#L404 > > > > > > > > I guess my question is more, who is supposed to set CBIE, CBCFE bits in the > > > > ENVCFG CSR. I.e. at it's default settings CMO instructions will cause > > > > illegal instructions until the level above does allow them. > > > > > > > > When the kernel wants to call a cache-invalidate, from my reading menvcfg > > > > needs to be modified accordingly - which would fall in SBI's court? > > > > > > > > > > I think so. I had the same question for the SSTC extension as well. > > > This is what I currently do: > > > > > > 1. Detect menvcfg first, detect stimecmp > > > 2. Enable SSTC feature only if both are available > > > 3. Set the STCE bit in menvcfg if SSTC is available > > > > > > Here is the patch > > > https://github.com/atishp04/opensbi/commit/e6b185821e8302bffdceb4633b413252e0de4889 > > > > Hmm, the CBO fields are defined as WARL (write any, read legal), > > so I guess some sort of trap won't work here. > > > > Correct. Traps for extensions that introduce new CSRs. > I was suggesting setting the corresponding bits in MENVCFG and reading > it again to check if it sticks. > > > The priv-spec only points to the cmo-spec for these bits and the cmo-spec > > does not specifiy what the value should be when cmo is not present. > > > > > > > > > In the future, zicbom can be detected in the same manner. However, > > > > > svpbmt is a bit tricky as it doesn't > > > > > define any new CSR. Do you think OpenSBI needs to detect svpbmt for any reason ? > > > > > > > > There is the PBMTE bit in MENVCFG, which I found while looking through the > > > > zicbom-parts, which is supposed to "control wheter svpbmt is available for > > > > use". So I guess the question is the same as above :-) > > > > > > > > > > PBMTE bit in MENVCFG says if PBMTE bit is available or not. OpenSBI > > > needs other way to > > > detect if PBMTE is available. > > > > > > That's why, I think MENVCFG should be set correctly by the hardware > > > upon reset. What do you think > > > about that ? I couldn't find anything related to the reset state for menvcfg. > > > > me neither. Both the priv-spec as well as the cmobase spec do not > > specifiy any reset-values it seems. > > > I have raised an issue in the ISA spec. > https://github.com/riscv/riscv-isa-manual/issues/820 > > > So I guess in the Qemu case, Qemu needs to set that bit when > > its svpbmt extension is enabled? > > > > We can do that if the priv spec is modified to allow that. > As per Greg's response, hardware is not expected to do that. So we have to dynamically detect the extensions in OpenSBI and write to menvcfg. I am not sure what needs to be done for CBIE bits as it both flush(01) or invalidate(11) are valid values > > > > Heiko > > > > > > > > > > > --- > > > > > > > arch/riscv/include/asm/hwcap.h | 18 ++++++++++++++++++ > > > > > > > arch/riscv/kernel/cpufeature.c | 27 ++++++++++++++++++++++++--- > > > > > > > 2 files changed, 42 insertions(+), 3 deletions(-) > > > > > > > > > > > > > > diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h > > > > > > > index 5ce50468aff1..170bd80da520 100644 > > > > > > > --- a/arch/riscv/include/asm/hwcap.h > > > > > > > +++ b/arch/riscv/include/asm/hwcap.h > > > > > > > @@ -34,7 +34,25 @@ extern unsigned long elf_hwcap; > > > > > > > #define RISCV_ISA_EXT_s ('s' - 'a') > > > > > > > #define RISCV_ISA_EXT_u ('u' - 'a') > > > > > > > > > > > > > > +/* > > > > > > > + * Increse this to higher value as kernel support more ISA extensions. > > > > > > > + */ > > > > > > > #define RISCV_ISA_EXT_MAX 64 > > > > > > > +#define RISCV_ISA_EXT_NAME_LEN_MAX 32 > > > > > > > + > > > > > > > +/* The base ID for multi-letter ISA extensions */ > > > > > > > +#define RISCV_ISA_EXT_BASE 26 > > > > > > > + > > > > > > > +/* > > > > > > > + * This enum represent the logical ID for each multi-letter RISC-V ISA extension. > > > > > > > + * The logical ID should start from RISCV_ISA_EXT_BASE and must not exceed > > > > > > > + * RISCV_ISA_EXT_MAX. 0-25 range is reserved for single letter > > > > > > > + * extensions while all the multi-letter extensions should define the next > > > > > > > + * available logical extension id. > > > > > > > + */ > > > > > > > +enum riscv_isa_ext_id { > > > > > > > + RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX, > > > > > > > +}; > > > > > > > > > > > > > > unsigned long riscv_isa_extension_base(const unsigned long *isa_bitmap); > > > > > > > > > > > > > > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c > > > > > > > index e9e3b0693d16..469b9739faf7 100644 > > > > > > > --- a/arch/riscv/kernel/cpufeature.c > > > > > > > +++ b/arch/riscv/kernel/cpufeature.c > > > > > > > @@ -83,7 +83,7 @@ void __init riscv_fill_hwcap(void) > > > > > > > > > > > > > > for_each_of_cpu_node(node) { > > > > > > > unsigned long this_hwcap = 0; > > > > > > > - unsigned long this_isa = 0; > > > > > > > + uint64_t this_isa = 0; > > > > > > > > > > > > > > if (riscv_of_processor_hartid(node) < 0) > > > > > > > continue; > > > > > > > @@ -169,12 +169,22 @@ void __init riscv_fill_hwcap(void) > > > > > > > if (*isa != '_') > > > > > > > --isa; > > > > > > > > > > > > > > +#define SET_ISA_EXT_MAP(name, bit) \ > > > > > > > + do { \ > > > > > > > + if ((ext_end - ext == sizeof(name) - 1) && \ > > > > > > > + !memcmp(ext, name, sizeof(name) - 1)) { \ > > > > > > > + this_isa |= (1UL << bit); \ > > > > > > > + pr_info("Found ISA extension %s", name);\ > > > > > > > + } \ > > > > > > > + } while (false) \ > > > > > > > + > > > > > > > if (unlikely(ext_err)) > > > > > > > continue; > > > > > > > if (!ext_long) { > > > > > > > this_hwcap |= isa2hwcap[(unsigned char)(*ext)]; > > > > > > > this_isa |= (1UL << (*ext - 'a')); > > > > > > > } > > > > > > > +#undef SET_ISA_EXT_MAP > > > > > > > } > > > > > > > > > > > > > > /* > > > > > > > @@ -187,10 +197,21 @@ void __init riscv_fill_hwcap(void) > > > > > > > else > > > > > > > elf_hwcap = this_hwcap; > > > > > > > > > > > > > > - if (riscv_isa[0]) > > > > > > > + if (riscv_isa[0]) { > > > > > > > +#if IS_ENABLED(CONFIG_32BIT) > > > > > > > + riscv_isa[0] &= this_isa & 0xFFFFFFFF; > > > > > > > + riscv_isa[1] &= this_isa >> 32; > > > > > > > +#else > > > > > > > riscv_isa[0] &= this_isa; > > > > > > > - else > > > > > > > +#endif > > > > > > > + } else { > > > > > > > +#if IS_ENABLED(CONFIG_32BIT) > > > > > > > + riscv_isa[0] = this_isa & 0xFFFFFFFF; > > > > > > > + riscv_isa[1] = this_isa >> 32; > > > > > > > +#else > > > > > > > riscv_isa[0] = this_isa; > > > > > > > +#endif > > > > > > > + } > > > > > > > } > > > > > > > > > > > > > > /* We don't support systems with F but without D, so mask those out > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
