Re: [PATCH v3 08/17] riscv: Introduce vendor variants of extension helpers

From: Conor Dooley
Date: Fri Apr 26 2024 - 12:20:19 EST

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On Sat, Apr 20, 2024 at 06:04:40PM -0700, Charlie Jenkins wrote:
> Vendor extensions are maintained in per-vendor structs (separate from
> standard extensions which live in riscv_isa). Create vendor variants for
> the existing extension helpers to interface with the riscv_isa_vendor
> bitmaps.

> There is a good amount of overlap between these functions, so
> the alternative checking code can be factored out.

Can you please split this out?

>
> Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> ---
> arch/riscv/errata/sifive/errata.c | 3 ++
> arch/riscv/errata/thead/errata.c | 3 ++
> arch/riscv/include/asm/cpufeature.h | 86 +++++++++++++++++-------------
> arch/riscv/include/asm/vendor_extensions.h | 56 +++++++++++++++++++
> arch/riscv/kernel/cpufeature.c | 20 ++++---
> arch/riscv/kernel/vendor_extensions.c | 40 ++++++++++++++
> 6 files changed, 164 insertions(+), 44 deletions(-)
>
> diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
> index 3d9a32d791f7..b29b6e405ff2 100644
> --- a/arch/riscv/errata/sifive/errata.c
> +++ b/arch/riscv/errata/sifive/errata.c
> @@ -12,6 +12,7 @@
> #include <asm/alternative.h>
> #include <asm/vendorid_list.h>
> #include <asm/errata_list.h>
> +#include <asm/vendor_extensions.h>
>
> struct errata_info_t {
> char name[32];
> @@ -99,6 +100,8 @@ void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> for (alt = begin; alt < end; alt++) {
> if (alt->vendor_id != SIFIVE_VENDOR_ID)
> continue;
> + if (alt->patch_id >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE)
> + continue;
> if (alt->patch_id >= ERRATA_SIFIVE_NUMBER) {
> WARN(1, "This errata id:%d is not in kernel errata list", alt->patch_id);
> continue;
> diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
> index b1c410bbc1ae..d8e78cc687bc 100644
> --- a/arch/riscv/errata/thead/errata.c
> +++ b/arch/riscv/errata/thead/errata.c
> @@ -18,6 +18,7 @@
> #include <asm/io.h>
> #include <asm/patch.h>
> #include <asm/vendorid_list.h>
> +#include <asm/vendor_extensions.h>
>
> static bool errata_probe_pbmt(unsigned int stage,
> unsigned long arch_id, unsigned long impid)
> @@ -163,6 +164,8 @@ void thead_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> for (alt = begin; alt < end; alt++) {
> if (alt->vendor_id != THEAD_VENDOR_ID)
> continue;
> + if (alt->patch_id >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE)
> + continue;

> if (alt->patch_id >= ERRATA_THEAD_NUMBER)

This number is 2, how does the patching actually work for vendor stuff
when the base is always greater than 2?

> continue;
>
> diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
> index db6a6d7d6b2e..83e1143db9ad 100644
> --- a/arch/riscv/include/asm/cpufeature.h
> +++ b/arch/riscv/include/asm/cpufeature.h
> @@ -103,22 +103,13 @@ bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, unsigned i
> __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_##ext)
>
> static __always_inline bool
> -riscv_has_extension_likely(const unsigned long ext)
> +__riscv_has_extension_likely_alternatives(const unsigned long vendor, const unsigned long ext)
> {
> - compiletime_assert(ext < RISCV_ISA_EXT_MAX,
> - "ext must be < RISCV_ISA_EXT_MAX");
> -
> - if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
> - asm goto(
> - ALTERNATIVE("j %l[l_no]", "nop", 0, %[ext], 1)
> - :
> - : [ext] "i" (ext)
> - :
> - : l_no);
> - } else {
> - if (!__riscv_isa_extension_available(NULL, ext))
> - goto l_no;
> - }
> + asm goto(ALTERNATIVE("j %l[l_no]", "nop", %[vendor], %[ext], 1)
> + :
> + : [vendor] "i" (vendor), [ext] "i" (ext)
> + :
> + : l_no);
>
> return true;
> l_no:
> @@ -126,42 +117,65 @@ riscv_has_extension_likely(const unsigned long ext)
> }
>
> static __always_inline bool
> -riscv_has_extension_unlikely(const unsigned long ext)
> +__riscv_has_extension_unlikely_alternatives(const unsigned long vendor, const unsigned long ext)

ngl, I think you could drop the _alternatives from these - the
likely/unlikely is only actually a thing because of the alternatives in
the first place & just retain the __ as a differentiator. That'd help
you with some of the long-line wrangling you've been doing below.

> {
> - compiletime_assert(ext < RISCV_ISA_EXT_MAX,
> - "ext must be < RISCV_ISA_EXT_MAX");
> -
> - if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
> - asm goto(
> - ALTERNATIVE("nop", "j %l[l_yes]", 0, %[ext], 1)
> - :
> - : [ext] "i" (ext)
> - :
> - : l_yes);
> - } else {
> - if (__riscv_isa_extension_available(NULL, ext))
> - goto l_yes;
> - }
> + asm goto(ALTERNATIVE("nop", "j %l[l_yes]", %[vendor], %[ext], 1)
> + :
> + : [vendor] "i" (vendor), [ext] "i" (ext)
> + :
> + : l_yes);
>
> return false;
> l_yes:
> return true;
> }
>
> +static __always_inline bool
> +riscv_has_extension_likely(const unsigned long ext)

Can you format this so that its on one line & wrap the arguments if
needs be?

> +{
> + compiletime_assert(ext < RISCV_ISA_EXT_MAX,
> + "ext must be < RISCV_ISA_EXT_MAX");
> +
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_likely_alternatives(0, ext);
> + else

I'm almost certain I said this before, but none of the else branches are
needed here, there's a return in the if branch, so the remainder of the
function becomes unconditionally executed.

> + return __riscv_isa_extension_available(NULL, ext);
> +}
> +
> +static __always_inline bool
> +riscv_has_extension_unlikely(const unsigned long ext)
> +{
> + compiletime_assert(ext < RISCV_ISA_EXT_MAX,
> + "ext must be < RISCV_ISA_EXT_MAX");
> +
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_unlikely_alternatives(0, ext);
> + else
> + return __riscv_isa_extension_available(NULL, ext);
> +}
> +
> static __always_inline bool riscv_cpu_has_extension_likely(int cpu, const unsigned long ext)
> {
> - if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_likely(ext))
> - return true;
> + compiletime_assert(ext < RISCV_ISA_EXT_MAX,
> + "ext must be < RISCV_ISA_EXT_MAX");
>
> - return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) &&
> + __riscv_has_extension_likely_alternatives(0, ext))

0 is meaningless, please make this more understandable using a define of
some sort.

> + return true;
> + else
> + return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
> }
>
> static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsigned long ext)
> {
> - if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) && riscv_has_extension_unlikely(ext))
> - return true;
> + compiletime_assert(ext < RISCV_ISA_EXT_MAX,
> + "ext must be < RISCV_ISA_EXT_MAX");
>
> - return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) &&
> + __riscv_has_extension_unlikely_alternatives(0, ext))
> + return true;
> + else
> + return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
> }
>
> #endif
> diff --git a/arch/riscv/include/asm/vendor_extensions.h b/arch/riscv/include/asm/vendor_extensions.h
> index 0af1ddd0af70..3e676a96016e 100644
> --- a/arch/riscv/include/asm/vendor_extensions.h
> +++ b/arch/riscv/include/asm/vendor_extensions.h
> @@ -23,4 +23,60 @@ extern const struct riscv_isa_vendor_ext_data_list *riscv_isa_vendor_ext_list[];
>
> extern const size_t riscv_isa_vendor_ext_list_size;
>
> +/*
> + * The alternatives need some way of distinguishing between vendor extensions
> + * and errata. Incrementing all of the vendor extension keys so they are at
> + * least 0x8000 accomplishes that.
> + */
> +#define RISCV_VENDOR_EXT_ALTERNATIVES_BASE 0x8000
> +
> +bool __riscv_isa_vendor_extension_available(int cpu, unsigned long vendor, unsigned int bit);
> +#define riscv_cpu_isa_vendor_extension_available(cpu, vendor, ext) \
> + __riscv_isa_vendor_extension_available(cpu, vendor, RISCV_ISA_VENDOR_EXT_##ext)
> +#define riscv_isa_vendor_extension_available(vendor, ext) \
> + __riscv_isa_vendor_extension_available(-1, vendor, RISCV_ISA_VENDOR_EXT_##ext)
> +
> +static __always_inline bool
> +riscv_has_vendor_extension_likely(const unsigned long vendor, const unsigned long ext)
> +{
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_likely_alternatives(vendor,
> + ext + RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
> + else
> + return __riscv_isa_vendor_extension_available(-1, vendor, ext);
> +}
> +
> +static __always_inline bool
> +riscv_has_vendor_extension_unlikely(const unsigned long vendor, const unsigned long ext)
> +{
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE))
> + return __riscv_has_extension_unlikely_alternatives(vendor,
> + ext + RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
> + else
> + return __riscv_isa_vendor_extension_available(-1, vendor, ext);
> +}
> +
> +static __always_inline bool riscv_cpu_has_vendor_extension_likely(const unsigned long vendor,
> + int cpu, const unsigned long ext)
> +{
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) &&
> + __riscv_has_extension_likely_alternatives(vendor,
> + ext + RISCV_VENDOR_EXT_ALTERNATIVES_BASE))
> + return true;
> + else
> + return __riscv_isa_vendor_extension_available(cpu, vendor, ext);
> +}
> +
> +static __always_inline bool riscv_cpu_has_vendor_extension_unlikely(const unsigned long vendor,
> + int cpu,
> + const unsigned long ext)
> +{
> + if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE) &&
> + __riscv_has_extension_unlikely_alternatives(vendor,
> + ext + RISCV_VENDOR_EXT_ALTERNATIVES_BASE))
> + return true;
> + else
> + return __riscv_isa_vendor_extension_available(cpu, vendor, ext);
> +}
> +
> #endif /* _ASM_VENDOR_EXTENSIONS_H */
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index c9f36822e337..17371887abcc 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -833,25 +833,29 @@ void __init_or_module riscv_cpufeature_patch_func(struct alt_entry *begin,
> {
> struct alt_entry *alt;
> void *oldptr, *altptr;
> - u16 id, value;
> + u16 id, value, vendor;
>
> if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> return;
>
> for (alt = begin; alt < end; alt++) {
> - if (alt->vendor_id != 0)
> - continue;
> -
> id = PATCH_ID_CPUFEATURE_ID(alt->patch_id);
> + vendor = PATCH_ID_CPUFEATURE_ID(alt->vendor_id);
>
> - if (id >= RISCV_ISA_EXT_MAX) {
> + if (id < RISCV_ISA_EXT_MAX) {

I think any reliance on the standard ext max requires a comment
explaining what the interaction is between it and the vendor stuff.

> + if (alt->vendor_id != 0)
> + continue;

If this happens, it's a bug, should we be continuing silently?

Cheers,
Conor.

> +
> + if (!__riscv_isa_extension_available(NULL, id))
> + continue;
> + } else if (id >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE) {
> + if (!__riscv_isa_vendor_extension_available(-1, vendor, id))
> + continue;
> + } else {
> WARN(1, "This extension id:%d is not in ISA extension list", id);
> continue;
> }
>
> - if (!__riscv_isa_extension_available(NULL, id))
> - continue;
> -
> value = PATCH_ID_CPUFEATURE_VALUE(alt->patch_id);
> if (!riscv_cpufeature_patch_check(id, value))
> continue;
> diff --git a/arch/riscv/kernel/vendor_extensions.c b/arch/riscv/kernel/vendor_extensions.c
> index f76cb3013c2d..eced93eec5a6 100644
> --- a/arch/riscv/kernel/vendor_extensions.c
> +++ b/arch/riscv/kernel/vendor_extensions.c
> @@ -3,6 +3,7 @@
> * Copyright 2024 Rivos, Inc
> */
>
> +#include <asm/vendorid_list.h>
> #include <asm/vendor_extensions.h>
> #include <asm/vendor_extensions/thead.h>
>
> @@ -16,3 +17,42 @@ const struct riscv_isa_vendor_ext_data_list *riscv_isa_vendor_ext_list[] = {
> };
>
> const size_t riscv_isa_vendor_ext_list_size = ARRAY_SIZE(riscv_isa_vendor_ext_list);
> +
> +/**
> + * __riscv_isa_vendor_extension_available() - Check whether given vendor
> + * extension is available or not.
> + *
> + * @cpu: check if extension is available on this cpu
> + * @vendor: vendor that the extension is a member of
> + * @bit: bit position of the desired extension
> + * Return: true or false
> + *
> + * NOTE: When cpu is -1, will check if extension is available on all cpus
> + */
> +bool __riscv_isa_vendor_extension_available(int cpu, unsigned long vendor, unsigned int bit)
> +{
> + unsigned long *bmap;
> + struct riscv_isainfo *cpu_bmap;
> + size_t bmap_size;
> +
> + switch (vendor) {
> +#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_THEAD
> + case THEAD_VENDOR_ID:
> + bmap = riscv_isa_vendor_ext_list_thead.vendor_bitmap;
> + cpu_bmap = riscv_isa_vendor_ext_list_thead.per_hart_vendor_bitmap;
> + bmap_size = riscv_isa_vendor_ext_list_thead.bitmap_size;
> + break;
> +#endif
> + default:
> + return false;
> + }
> +
> + if (cpu != -1)
> + bmap = cpu_bmap[cpu].isa;
> +
> + if (bit >= bmap_size)
> + return false;
> +
> + return test_bit(bit, bmap) ? true : false;
> +}
> +EXPORT_SYMBOL_GPL(__riscv_isa_vendor_extension_available);
>
> --
> 2.44.0
>

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