* [PATCH for 4.21 v7 4/4] xen/riscv: identify specific ISA supported by cpu
2025-02-20 17:44 [PATCH for 4.21 v7 0/4] RISC-V runtime detection of extenstions Oleksii Kurochko
` (2 preceding siblings ...)
2025-02-20 17:44 ` [PATCH for 4.21 v7 3/4] xen/riscv: make zbb as mandatory Oleksii Kurochko
@ 2025-02-20 17:44 ` Oleksii Kurochko
2025-02-21 17:02 ` [PATCH for 4.21 v7 0.5/4] xen/README: add compiler and binutils versions for RISCV-64 Oleksii Kurochko
4 siblings, 0 replies; 18+ messages in thread
From: Oleksii Kurochko @ 2025-02-20 17:44 UTC (permalink / raw)
To: xen-devel
Cc: Oleksii Kurochko, Alistair Francis, Bob Eshleman, Connor Davis,
Andrew Cooper, Anthony PERARD, Michal Orzel, Jan Beulich,
Julien Grall, Roger Pau Monné, Stefano Stabellini
Supported ISA extensions are specified in the device tree within the CPU
node, using two properties: `riscv,isa-extensions` and `riscv,isa`.
Currently, Xen does not support the `riscv,isa-extensions` property and
will be added in the future.
The `riscv,isa` property is parsed for each CPU, and the common extensions
are stored in the `host_riscv_isa` bitmap.
This bitmap is then used by `riscv_isa_extension_available()` to check
if a specific extension is supported.
The current implementation is based on Linux kernel v6.12-rc3
implementation with the following changes:
- Drop unconditional setting of {RISCV_ISA_EXT_ZICSR,
RISCV_ISA_EXT_ZIFENCEI, RISCV_ISA_EXT_ZICNTR, RISCV_ISA_EXT_ZIHPM} because
Xen is going to run on hardware produced after the aforementioned
extensions were split out of "i".
- Remove saving of the ISA for each CPU, only the common available ISA is
saved.
- Remove ACPI-related code as ACPI is not supported by Xen.
- Drop handling of elf_hwcap, since Xen does not provide hwcap to
userspace.
- Replace of_cpu_device_node_get() API, which is not available in Xen,
with a combination of dt_for_each_child_node(), dt_device_type_is_equal(),
and dt_get_cpuid_from_node() to retrieve cpuid and riscv,isa in
riscv_fill_hwcap_from_isa_string().
- Rename arguments of __RISCV_ISA_EXT_DATA() from _name to ext_name, and
_id to ext_id for clarity.
- Replace instances of __RISCV_ISA_EXT_DATA with RISCV_ISA_EXT_DATA.
- Replace instances of __riscv_isa_extension_available with
riscv_isa_extension_available for consistency. Also, update the type of
`bit` argument of riscv_isa_extension_available().
- Redefine RISCV_ISA_EXT_DATA() to work only with ext_name and ext_id,
as other fields are not used in Xen currently. Also RISCV_ISA_EXT_DATA()
is reworked in the way to take only one argument `ext_name`.
- Add check of first 4 letters of riscv,isa string to
riscv_isa_parse_string() as Xen doesn't do this check before so it is
necessary to check correctness of riscv,isa string. ( it should start with
rv{32,64} with taking into account upper and lower case of "rv").
Additionally, check also that 'i' goes after 'rv{32,64}' to be sure that
`out_bitmap` can't be empty.
- Drop an argument of riscv_fill_hwcap() and riscv_fill_hwcap_from_isa_string()
as it isn't used, at the moment.
- Update the comment message about QEMU workaround.
- Apply Xen coding style.
- s/pr_info/printk.
- Drop handling of uppercase letters of riscv,isa in riscv_isa_parse_string() as
Xen checks that riscv,isa should be in lowercase according to the device tree
bindings.
- Update logic of riscv_isa_parse_string(): now it stops parsing of riscv,isa
if illegal symbol was found instead of ignoring them.
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
Changes in V7:
- Add blanks around '##' in RISCV_ISA_EXT_DATA macros.
- Add zba and zbs to riscv_isa_ext[] as we have such in enumerators so
someone could try to ask if it is supported or not by CPU.
- Fix the comment, start from uppercase letter.
- Add Acked-by: Jan Beulich <jbeulich@suse.com>.
---
Changes in V6:
- Explicitly set ZBA, ZBB, ZBS extensions if `b` is present in riscv,isa.
- Update enum riscv_isa_ext_id; not an extension name is in lowercase.
- Update RISCV_ISA_EXT_DATA() macro to recieve only one argument.
- Add __init for is_lowercase_extension_name().
- Indent label by one blank.
- Add quotes around %c.
- Drop extensions 'f' and 'd' from required_extensions[] array.
- Update the commit message.
---
Changes in V5:
- Add IMAFD + zifencei extensions to required_extensions[] as we are using
-maarch=rv64g* for compilation.
- Add "C" extension to required_extensions[] as if CONFIG_RISCV_ISA_C=y
then -march will be = rv64gc*.
- Fix typos.
- s/strncmp/memcmp.
- Drop usage of ext_err and reuse ext_end instead.
- Drop tolower() functions as we guarante that riscv,isa will be in lower case.
- Declare req_extns_amount as const.
- Check what riscv_isa_parse_string() returns.
- Add check that Vendor extensions (case 'x') name is alnum.
- Return -EINVAL from riscv_isa_parse_string() if an extension has wrong name.
- Update logic of riscv_isa_parse_string(): now it stop parsing of riscv,isa
if illegal symbol was found instead of ignoring them.
- Drop ASSERT ASSERT(!bitmap_empty(this_isa, RISCV_ISA_EXT_MAX)) as now
riscv_isa_parse_string() has a check which guarantes that, at least, "rv{32,64}i"
is in "riscv,isa" thereby this_isa can't be empty.
- Update the commit message.
---
Changes in V4:
- Add "Originally ... " at the start of cpufeature.c.
- Sync required_extensions[] with riscv_isa_ext[] in terms of element
sorting/ordering.
- Fix identations.
- s/#error/# error.
- With insisting on ISA string being all lowercase, drop handling the
uppercases in riscv_isa_parse_string().
- check riscv,isa recieved from device tree; it must be in lowercase.
- Update ASSERT() in match_isa_ext(): drop checking of riscv,isa recieved from
device tree as this check was moved to riscv_fill_hwcap().
- Update is_lowercase_extension_name() to ignore digits as they could be used
for extension version which is part of the extension name so should be
skipped.
- Alight ternanry operator properly in riscv_fill_hwcap().
- Update the commit message: add information that handling of uppercase letters
in riscv,isa are dropped in riscv_isa_parsing_string() becase Xen checks that
riscv,isa must be all in lowercase according to device tree binding.
---
Changes in V3:
- Drop description of changes in cpufeature.c and leave only in the commit
message to not deal with possible staleness of them in the future.
- Update for dt_get_cpuid_from_node():
- update printk() message.
- add some explanation about if-condition on the start of the function.
- add dt_cpuid argument for function dt_get_cpuid_from_node() to deal
with potential truncation issue from paddr_t (dt_read_paddr() returns
that ) to int.
- Add Zicsr to required_extensions[].
- Drop an argument check at the start of is_lowercase_extension_name()
as function is static and callers are expected to pass a good pointer.
- Add a comment with some additional explanation about the stop condition
of checking a case of extension name.
- Omit blanks after opening and closing parentheses in the comments.
- Add missed parentheses in match_isa_ext().
- Drop ASSERT() which checks that first two letters of `isa` string are in
lower case as after this ASSERT() there is an if-condition which does the
same.
- Cut part of printk_once()'s message in riscv_isa_parse_string() related
to riscv,isa-extension as it isn't supported for now and usage of it will
lead to panic().
- Drop function riscv_fill_hwcap_from_ext_list() at all as Xen isn't going
to support riscv,isa-extensions for now.
- Clarify printk()'s message when riscv,isa property wasn't found in cpu node.
Now it contains "for DT's cpu%d node", where %d is cpuid, instead of
"for cpu%d" to not confuse cpuid number ( if it Xen's cpu id and physical
cpu's id).
- Updates in riscv_isa_extension_available():
- Drop local varible `bmap` and initialize `isa_bitmap` in more readable way.
- Rename argument `bit` of riscv_isa_extension_available() to `id` for
clearness.
- Update handling of failure of h/w capabilities parsing in riscv_fill_hwcap().
- Introduce has_isa_extensions_property() to check if "riscv,isa-extension" is
present in any device tree cpu node.
---
Changes in V2:
- Update the list of changes in comparison with Linux on the top of
cpufeature.c.
- Now really drop all ACPI-related stuff.
Add #ifdef CONFIG_ACPI #error ... #endif instead.
- Make `id` ( member of riscv_isa_ext_data structure ) not const.
- s/__read_mostly/__ro_after_init for riscv_isa bitmap.
- Update the comment above riscv_isa_ext[] declaration:
- Drop Linux details.
- Revised the numbering of the ordering rules for RISC-V ISA extensions.
- Add comment that extension name must be all lowercase according to
device tree binding.
- Add __initconst for declarations of riscv_isa_ext[] and
required_extensions[].
- Move riscv_isa_ext_count for global declaration to match_isa_ext where
it is really used.
- Add new function is_lowercase_extension_name().
- Updates for match_isa_ext():
- Move last argument of match_isa_ext() to new line to not violate line
length.
- s/int/unsigned int for cycle varible `i`.
- s/set_bit/__set_bit as no need for atomicity at this stage of boot.
- Add ASSERT() to be sure that extension name is in lowercase.
- s/strncasecmp/strncasecmp as extension name must be in a lowercase.
- Updates for riscv_isa_parse_string():
- Move last argument of riscv_isa_parse_string() to new line to not violate
line length.
- Update the checks at the start of the function. Now if CONFIG_RISCV_32=y
the only rv32 is accepted, or rv64 for CONFIG_RISCV_64=y.
- Drop ACPI-related stuff.
- Add blank lines between non-fall-through case blocks.
- Add blanks in `for loops` before ')'.
- Update the comment about QEMU workaround for invalid single-letter
's' & 'u'.
- Updates for riscv_fill_hwcap_from_ext_list():
- Drop initilizer of cpuid inside dt_for_each_child_node() {...}.
- Introduce res and return it instead of -EINVAL.
- Drop `else` and change printk("riscv,isa-extensions isnt supported\n")
to panic("riscv,isa-extensions isnt supported\n").
- Drop ( cpuid >= NR_CPUS ) check as cpuid technically could be any
number. Only cpuid=0 is guaranteed to be.
- Updates for riscv_fill_hwcap_from_isa_string():
- move cpuid and isa variables to dt_for_each_child_node() {...}.
- Drop initilizer of cpuid inside dt_for_each_child_node() {...}.
- Drop ( cpuid >= NR_CPUS ) check as cpuid technically could be any
number. Only cpuid=0 is guaranteed to be.
- Add ASSERT() to be sure that `this_isa` isn't null to prevent ending up
with extensions not supported by one of the CPUs.
- Updates for riscv_isa_extension_available():
- Code style fixes.
- Drop conditional operator used in return as functions returns bool.
- s/extenstion/extensions, s/extenstion/extenstion.
- Drop RISCV_ISA_EXT_SxAIA as it isn't used.
- Move definitions of RISCV_ISA_EXT_{a,c,d,...,v} to enum riscv_isa_ext_id.
- Move macros RISCV_ISA_EXT_MAX to enum riscv_isa_ext_id.
- Update the comment above definition of RISCV_ISA_EXT_BASE.
- Fix code style ( violation of line length ) for
riscv_isa_extension_available().
- Sync commit message with the comment on the start of cpufeature.c
---
xen/arch/riscv/Makefile | 1 +
xen/arch/riscv/cpufeature.c | 504 ++++++++++++++++++++++++
xen/arch/riscv/include/asm/cpufeature.h | 59 +++
xen/arch/riscv/setup.c | 3 +
4 files changed, 567 insertions(+)
create mode 100644 xen/arch/riscv/cpufeature.c
create mode 100644 xen/arch/riscv/include/asm/cpufeature.h
diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index a5eb2aed4b..b0c8270a99 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -1,3 +1,4 @@
+obj-y += cpufeature.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-y += entry.o
obj-y += mm.o
diff --git a/xen/arch/riscv/cpufeature.c b/xen/arch/riscv/cpufeature.c
new file mode 100644
index 0000000000..bf09aa1170
--- /dev/null
+++ b/xen/arch/riscv/cpufeature.c
@@ -0,0 +1,504 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Originally taken for Linux kernel v6.12-rc3.
+ *
+ * Copyright (C) 2015 ARM Ltd.
+ * Copyright (C) 2017 SiFive
+ * Copyright (C) 2024 Vates
+ */
+
+#include <xen/bitmap.h>
+#include <xen/ctype.h>
+#include <xen/device_tree.h>
+#include <xen/errno.h>
+#include <xen/init.h>
+#include <xen/lib.h>
+#include <xen/sections.h>
+
+#include <asm/cpufeature.h>
+
+#ifdef CONFIG_ACPI
+# error "cpufeature.c functions should be updated to support ACPI"
+#endif
+
+struct riscv_isa_ext_data {
+ unsigned int id;
+ const char *name;
+};
+
+#define RISCV_ISA_EXT_DATA(ext_name) \
+{ \
+ .id = RISCV_ISA_EXT_ ## ext_name, \
+ .name = #ext_name, \
+}
+
+/* Host ISA bitmap */
+static __ro_after_init DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX);
+
+static int __init dt_get_cpuid_from_node(const struct dt_device_node *cpu,
+ unsigned long *dt_cpuid)
+{
+ const __be32 *prop;
+ unsigned int reg_len;
+
+ /*
+ * For debug purpose check dt_n_size_cells(cpu) value.
+ *
+ * Based on DT's bindings [1] and RISC-V's DTS files in kernel #size-cells
+ * for cpu node is expected to be 0.
+ *
+ * [1] https://www.kernel.org/doc/Documentation/devicetree/bindings/riscv/cpus.txt
+ */
+ if ( dt_n_size_cells(cpu) != 0 )
+ printk("DT's cpu node `%s`: #size-cells %d\n",
+ dt_node_full_name(cpu), dt_n_size_cells(cpu));
+
+ prop = dt_get_property(cpu, "reg", ®_len);
+ if ( !prop )
+ {
+ printk("cpu node `%s`: has no reg property\n", dt_node_full_name(cpu));
+ return -EINVAL;
+ }
+
+ if ( reg_len < dt_cells_to_size(dt_n_addr_cells(cpu)) )
+ {
+ printk("cpu node `%s`: reg property too short\n",
+ dt_node_full_name(cpu));
+ return -EINVAL;
+ }
+
+ /*
+ * It is safe to convert `paddr_t` to `unsigned long` as dt_read_paddr()
+ * in the context of this function returns cpuid which according to RISC-V
+ * specification could be from 0 to ((1ULL << (MXLEN)) - 1), where
+ * MXLEN=32 for RV32 and MXLEN=64 for RV64.
+ */
+ *dt_cpuid = dt_read_paddr(prop, dt_n_addr_cells(cpu));
+
+ return 0;
+}
+
+/*
+ * The canonical order of ISA extension names in the ISA string is defined in
+ * chapter 27 of the unprivileged specification.
+ *
+ * The specification uses vague wording, such as should, when it comes to
+ * ordering, so for our purposes the following rules apply:
+ *
+ * 1. All multi-letter extensions must be separated from other extensions by an
+ * underscore.
+ *
+ * 2. Additional standard extensions (starting with 'Z') must be sorted after
+ * single-letter extensions and before any higher-privileged extensions.
+ *
+ * 3. The first letter following the 'Z' conventionally indicates the most
+ * closely related alphabetical extension category, IMAFDQLCBKJTPVH.
+ * If multiple 'Z' extensions are named, they must be ordered first by
+ * category, then alphabetically within a category.
+ *
+ * 4. Standard supervisor-level extensions (starting with 'S') must be listed
+ * after standard unprivileged extensions. If multiple supervisor-level
+ * extensions are listed, they must be ordered alphabetically.
+ *
+ * 5. Standard machine-level extensions (starting with 'Zxm') must be listed
+ * after any lower-privileged, standard extensions. If multiple
+ * machine-level extensions are listed, they must be ordered
+ * alphabetically.
+ *
+ * 6. Non-standard extensions (starting with 'X') must be listed after all
+ * standard extensions. If multiple non-standard extensions are listed, they
+ * must be ordered alphabetically.
+ *
+ * An example string following the order is:
+ * rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux
+ *
+ * New entries to this struct should follow the ordering rules described above.
+ *
+ * Extension name must be all lowercase (according to device-tree binding)
+ * and strncmp() is used in match_isa_ext() to compare extension names instead
+ * of strncasecmp().
+ */
+const struct riscv_isa_ext_data __initconst riscv_isa_ext[] = {
+ RISCV_ISA_EXT_DATA(i),
+ RISCV_ISA_EXT_DATA(m),
+ RISCV_ISA_EXT_DATA(a),
+ RISCV_ISA_EXT_DATA(f),
+ RISCV_ISA_EXT_DATA(d),
+ RISCV_ISA_EXT_DATA(q),
+ RISCV_ISA_EXT_DATA(c),
+ RISCV_ISA_EXT_DATA(h),
+ RISCV_ISA_EXT_DATA(zicntr),
+ RISCV_ISA_EXT_DATA(zicsr),
+ RISCV_ISA_EXT_DATA(zifencei),
+ RISCV_ISA_EXT_DATA(zihintpause),
+ RISCV_ISA_EXT_DATA(zihpm),
+ RISCV_ISA_EXT_DATA(zba),
+ RISCV_ISA_EXT_DATA(zbb),
+ RISCV_ISA_EXT_DATA(zbs),
+ RISCV_ISA_EXT_DATA(smaia),
+ RISCV_ISA_EXT_DATA(ssaia),
+};
+
+static const struct riscv_isa_ext_data __initconst required_extensions[] = {
+ RISCV_ISA_EXT_DATA(i),
+ RISCV_ISA_EXT_DATA(m),
+ RISCV_ISA_EXT_DATA(a),
+#ifdef CONFIG_RISCV_ISA_C
+ RISCV_ISA_EXT_DATA(c),
+#endif
+ RISCV_ISA_EXT_DATA(zicsr),
+ RISCV_ISA_EXT_DATA(zifencei),
+ RISCV_ISA_EXT_DATA(zihintpause),
+ RISCV_ISA_EXT_DATA(zbb),
+};
+
+static bool __init is_lowercase_extension_name(const char *str)
+{
+ /*
+ * `str` could contain full riscv,isa string from device tree so one
+ * of the stop conditions is checking for '_' as extensions are
+ * separated by '_'.
+ */
+ for ( unsigned int i = 0; (str[i] != '\0') && (str[i] != '_'); i++ )
+ if ( !isdigit(str[i]) && !islower(str[i]) )
+ return false;
+
+ return true;
+}
+
+static void __init match_isa_ext(const char *name, const char *name_end,
+ unsigned long *bitmap)
+{
+ const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext);
+
+ for ( unsigned int i = 0; i < riscv_isa_ext_count; i++ )
+ {
+ const struct riscv_isa_ext_data *ext = &riscv_isa_ext[i];
+
+ /*
+ * `ext->name` (according to initialization of riscv_isa_ext[]
+ * elements) must be all in lowercase.
+ */
+ ASSERT(is_lowercase_extension_name(ext->name));
+
+ if ( (name_end - name == strlen(ext->name)) &&
+ !memcmp(name, ext->name, name_end - name) )
+ {
+ __set_bit(ext->id, bitmap);
+ break;
+ }
+ }
+}
+
+static int __init riscv_isa_parse_string(const char *isa,
+ unsigned long *out_bitmap)
+{
+ if ( (isa[0] != 'r') && (isa[1] != 'v') )
+ return -EINVAL;
+
+#if defined(CONFIG_RISCV_32)
+ if ( isa[2] != '3' && isa[3] != '2' )
+ return -EINVAL;
+#elif defined(CONFIG_RISCV_64)
+ if ( isa[2] != '6' && isa[3] != '4' )
+ return -EINVAL;
+#else
+# error "unsupported RISC-V bitness"
+#endif
+
+ /*
+ * In unpriv. specification (*_20240411) is mentioned the following:
+ * (1) A RISC-V ISA is defined as a base integer ISA, which must be
+ * present in any implementation, plus optional extensions to
+ * the base ISA.
+ * (2) Chapter 6 describes the RV32E and RV64E subset variants of
+ * the RV32I or RV64I base instruction sets respectively, which
+ * have been added to support small microcontrollers, and which
+ * have half the number of integer registers.
+ *
+ * What means that isa should contain, at least, I or E.
+ *
+ * As Xen isn't expected to be run on microcontrollers and according
+ * to device tree binding the first extension should be "i".
+ */
+ if ( isa[4] != 'i' )
+ return -EINVAL;
+
+ isa += 4;
+
+ while ( *isa )
+ {
+ const char *ext = isa++;
+ const char *ext_end = isa;
+
+ switch ( *ext )
+ {
+ case 'x':
+ printk_once("Vendor extensions are ignored in riscv,isa\n");
+ /*
+ * To skip an extension, we find its end.
+ * As multi-letter extensions must be split from other multi-letter
+ * extensions with an "_", the end of a multi-letter extension will
+ * either be the null character or the "_" at the start of the next
+ * multi-letter extension.
+ */
+ for ( ; *isa && *isa != '_'; ++isa )
+ if ( unlikely(!isalnum(*isa)) )
+ goto riscv_isa_parse_string_err;
+
+ ext_end = NULL;
+ break;
+
+ case 's':
+ /*
+ * Workaround for invalid single-letter 's' & 'u' (QEMU):
+ * Before QEMU 7.1 it was an issue with misa to ISA string
+ * conversion:
+ * https://patchwork.kernel.org/project/qemu-devel/patch/dee09d708405075420b29115c1e9e87910b8da55.1648270894.git.research_trasio@irq.a4lg.com/#24792587
+ * Additional details of the workaround on Linux kernel side:
+ * https://lore.kernel.org/linux-riscv/ae93358e-e117-b43d-faad-772c529f846c@irq.a4lg.com/#t
+ *
+ * No need to set the bit in riscv_isa as 's' & 'u' are
+ * not valid ISA extensions. It works unless the first
+ * multi-letter extension in the ISA string begins with
+ * "Su" and is not prefixed with an underscore.
+ */
+ if ( ext[-1] != '_' && ext[1] == 'u' )
+ {
+ ++isa;
+ ext_end = NULL;
+ break;
+ }
+ fallthrough;
+ case 'z':
+ /*
+ * Before attempting to parse the extension itself, we find its end.
+ * As multi-letter extensions must be split from other multi-letter
+ * extensions with an "_", the end of a multi-letter extension will
+ * either be the null character or the "_" at the start of the next
+ * multi-letter extension.
+ *
+ * Next, as the extensions version is currently ignored, we
+ * eliminate that portion. This is done by parsing backwards from
+ * the end of the extension, removing any numbers. This may be a
+ * major or minor number however, so the process is repeated if a
+ * minor number was found.
+ *
+ * ext_end is intended to represent the first character *after* the
+ * name portion of an extension, but will be decremented to the last
+ * character itself while eliminating the extensions version number.
+ * A simple re-increment solves this problem.
+ */
+ for ( ; *isa && *isa != '_'; ++isa )
+ if ( unlikely(!isalnum(*isa)) )
+ goto riscv_isa_parse_string_err;
+
+ ext_end = isa;
+
+ if ( !isdigit(ext_end[-1]) )
+ break;
+
+ while ( isdigit(*--ext_end) )
+ ;
+
+ if ( ext_end[0] != 'p' || !isdigit(ext_end[-1]) )
+ {
+ ++ext_end;
+ break;
+ }
+
+ while ( isdigit(*--ext_end) )
+ ;
+
+ ++ext_end;
+ break;
+
+ /*
+ * If someone mentioned `b` extension in riscv,isa instead of Zb{a,b,s}
+ * explicitly then set bits exlicitly in out_bitmap to satisfy
+ * requirement of Zbb (mentioned in required_extensions[]).
+ */
+ case 'b':
+ __set_bit(RISCV_ISA_EXT_zba, out_bitmap);
+ __set_bit(RISCV_ISA_EXT_zbb, out_bitmap);
+ __set_bit(RISCV_ISA_EXT_zbs, out_bitmap);
+ fallthrough;
+ default:
+ /*
+ * Things are a little easier for single-letter extensions, as they
+ * are parsed forwards.
+ *
+ * After checking that our starting position is valid, we need to
+ * ensure that, when isa was incremented at the start of the loop,
+ * that it arrived at the start of the next extension.
+ *
+ * If we are already on a non-digit, there is nothing to do. Either
+ * we have a multi-letter extension's _, or the start of an
+ * extension.
+ *
+ * Otherwise we have found the current extension's major version
+ * number. Parse past it, and a subsequent p/minor version number
+ * if present. The `p` extension must not appear immediately after
+ * a number, so there is no fear of missing it.
+ */
+ if ( unlikely(!isalpha(*ext)) )
+ goto riscv_isa_parse_string_err;
+
+ if ( !isdigit(*isa) )
+ break;
+
+ while ( isdigit(*++isa) )
+ ;
+
+ if ( *isa != 'p' )
+ break;
+
+ if ( !isdigit(*++isa) )
+ {
+ --isa;
+ break;
+ }
+
+ while ( isdigit(*++isa) )
+ ;
+
+ break;
+ }
+
+ /*
+ * The parser expects that at the start of an iteration isa points to the
+ * first character of the next extension. As we stop parsing an extension
+ * on meeting a non-alphanumeric character, an extra increment is needed
+ * where the succeeding extension is a multi-letter prefixed with an "_".
+ */
+ if ( *isa == '_' )
+ ++isa;
+
+ if ( unlikely(!ext_end) )
+ continue;
+
+ match_isa_ext(ext, ext_end, out_bitmap);
+ }
+
+ return 0;
+
+ riscv_isa_parse_string_err:
+ printk("illegal symbol '%c' in riscv,isa string\n", *isa);
+ return -EINVAL;
+}
+
+static void __init riscv_fill_hwcap_from_isa_string(void)
+{
+ const struct dt_device_node *cpus = dt_find_node_by_path("/cpus");
+ const struct dt_device_node *cpu;
+
+ if ( !cpus )
+ {
+ printk("Missing /cpus node in the device tree?\n");
+ return;
+ }
+
+ dt_for_each_child_node(cpus, cpu)
+ {
+ DECLARE_BITMAP(this_isa, RISCV_ISA_EXT_MAX);
+ const char *isa;
+ unsigned long cpuid;
+
+ if ( !dt_device_type_is_equal(cpu, "cpu") )
+ continue;
+
+ if ( dt_get_cpuid_from_node(cpu, &cpuid) < 0 )
+ continue;
+
+ if ( dt_property_read_string(cpu, "riscv,isa", &isa) )
+ {
+ printk("Unable to find \"riscv,isa\" devicetree entry "
+ "for DT's cpu%ld node\n", cpuid);
+ continue;
+ }
+
+ for ( unsigned int i = 0; (isa[i] != '\0'); i++ )
+ if ( !isdigit(isa[i]) && (isa[i] != '_') && !islower(isa[i]) )
+ panic("According to DT binding riscv,isa must be lowercase\n");
+
+ if ( riscv_isa_parse_string(isa, this_isa) )
+ panic("Check riscv,isa in dts file\n");
+
+ if ( bitmap_empty(riscv_isa, RISCV_ISA_EXT_MAX) )
+ bitmap_copy(riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
+ else
+ bitmap_and(riscv_isa, riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
+ }
+}
+
+static bool __init has_isa_extensions_property(void)
+{
+ const struct dt_device_node *cpus = dt_find_node_by_path("/cpus");
+ const struct dt_device_node *cpu;
+
+ if ( !cpus )
+ {
+ printk("Missing /cpus node in the device tree?\n");
+ return false;
+ }
+
+ dt_for_each_child_node(cpus, cpu)
+ {
+ const char *isa;
+
+ if ( !dt_device_type_is_equal(cpu, "cpu") )
+ continue;
+
+ if ( dt_property_read_string(cpu, "riscv,isa-extensions", &isa) )
+ continue;
+
+ return true;
+ }
+
+ return false;
+}
+
+bool riscv_isa_extension_available(const unsigned long *isa_bitmap,
+ enum riscv_isa_ext_id id)
+{
+ if ( !isa_bitmap )
+ isa_bitmap = riscv_isa;
+
+ if ( id >= RISCV_ISA_EXT_MAX )
+ return false;
+
+ return test_bit(id, isa_bitmap);
+}
+
+void __init riscv_fill_hwcap(void)
+{
+ unsigned int i;
+ const size_t req_extns_amount = ARRAY_SIZE(required_extensions);
+ bool all_extns_available = true;
+
+ riscv_fill_hwcap_from_isa_string();
+
+ if ( bitmap_empty(riscv_isa, RISCV_ISA_EXT_MAX) )
+ {
+ const char *failure_msg = has_isa_extensions_property() ?
+ "\"riscv,isa-extension\" isn't supported" :
+ "\"riscv,isa\" parsing failed";
+
+ panic("HW capabilities parsing failed: %s\n", failure_msg);
+ }
+
+ for ( i = 0; i < req_extns_amount; i++ )
+ {
+ const struct riscv_isa_ext_data ext = required_extensions[i];
+
+ if ( !riscv_isa_extension_available(NULL, ext.id) )
+ {
+ printk("Xen requires extension: %s\n", ext.name);
+ all_extns_available = false;
+ }
+ }
+
+ if ( !all_extns_available )
+ panic("Look why the extensions above are needed in "
+ "https://xenbits.xenproject.org/docs/unstable/misc/riscv/booting.txt\n");
+}
diff --git a/xen/arch/riscv/include/asm/cpufeature.h b/xen/arch/riscv/include/asm/cpufeature.h
new file mode 100644
index 0000000000..1015b6ee44
--- /dev/null
+++ b/xen/arch/riscv/include/asm/cpufeature.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef ASM__RISCV__CPUFEATURE_H
+#define ASM__RISCV__CPUFEATURE_H
+
+#ifndef __ASSEMBLY__
+
+#include <xen/stdbool.h>
+
+/*
+ * These macros represent the logical IDs of each multi-letter RISC-V ISA
+ * extension and are used in the ISA bitmap. The logical IDs start from
+ * RISCV_ISA_EXT_BASE, which allows the 0-25 range to be reserved for single
+ * letter extensions and are used in enum riscv_isa_ext_id.
+ *
+ * New extensions should just be added to the bottom, rather than added
+ * alphabetically, in order to avoid unnecessary shuffling.
+ */
+#define RISCV_ISA_EXT_BASE 26
+
+enum riscv_isa_ext_id {
+ RISCV_ISA_EXT_a,
+ RISCV_ISA_EXT_c,
+ RISCV_ISA_EXT_d,
+ RISCV_ISA_EXT_f,
+ RISCV_ISA_EXT_h,
+ RISCV_ISA_EXT_i,
+ RISCV_ISA_EXT_m,
+ RISCV_ISA_EXT_q,
+ RISCV_ISA_EXT_v,
+ RISCV_ISA_EXT_zicntr = RISCV_ISA_EXT_BASE,
+ RISCV_ISA_EXT_zicsr,
+ RISCV_ISA_EXT_zifencei,
+ RISCV_ISA_EXT_zihintpause,
+ RISCV_ISA_EXT_zihpm,
+ RISCV_ISA_EXT_zba,
+ RISCV_ISA_EXT_zbb,
+ RISCV_ISA_EXT_zbs,
+ RISCV_ISA_EXT_smaia,
+ RISCV_ISA_EXT_ssaia,
+ RISCV_ISA_EXT_MAX
+};
+
+void riscv_fill_hwcap(void);
+
+bool riscv_isa_extension_available(const unsigned long *isa_bitmap,
+ enum riscv_isa_ext_id id);
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* ASM__RISCV__CPUFEATURE_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
index f2b6e684ac..b0e587678e 100644
--- a/xen/arch/riscv/setup.c
+++ b/xen/arch/riscv/setup.c
@@ -13,6 +13,7 @@
#include <public/version.h>
+#include <asm/cpufeature.h>
#include <asm/early_printk.h>
#include <asm/fixmap.h>
#include <asm/sbi.h>
@@ -123,6 +124,8 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
panic("Booting using ACPI isn't supported\n");
}
+ riscv_fill_hwcap();
+
printk("All set up\n");
machine_halt();
--
2.48.1
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