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RISCV_HWPROBE_KEY_CPUPERF_0 was mistakenly flagged as a bitmask in
hwprobe_key_is_bitmask(), when in reality it was an enum value. This
causes problems when used in conjunction with RISCV_HWPROBE_WHICH_CPUS,
since SLOW, FAST, and EMULATED have values whose bits overlap with
each other. If the caller asked for the set of CPUs that was SLOW or
EMULATED, the returned set would also include CPUs that were FAST.
Introduce a new hwprobe key, RISCV_HWPROBE_KEY_MISALIGNED_PERF, which
returns the same values in response to a direct query (with no flags),
but is properly handled as an enumerated value. As a result, SLOW,
FAST, and EMULATED are all correctly treated as distinct values under
the new key when queried with the WHICH_CPUS flag.
Leave the old key in place to avoid disturbing applications which may
have already come to rely on the key, with or without its broken
behavior with respect to the WHICH_CPUS flag.
Fixes: e178bf146e4b ("RISC-V: hwprobe: Introduce which-cpus flag")
Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240809214444.3257596-2-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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The RISC-V architecture makes a real time counter CSR (via RDTIME
instruction) available for applications in U-mode but there is no
architected mechanism for an application to discover the frequency
the counter is running at. Some applications (e.g., DPDK) use the
time counter for basic performance analysis as well as fine grained
time-keeping.
Add support to the hwprobe system call to export the time CSR
frequency to code running in U-mode.
Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Acked-by: Punit Agrawal <punit.agrawal@bytedance.com>
Link: https://lore.kernel.org/r/20240702033731.71955-2-cuiyunhui@bytedance.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Some userspace applications (OpenJDK for instance) uses the free MSBs
in pointers to insert additional information for their own logic and
need to get this information from somewhere. Currently they rely on
parsing /proc/cpuinfo "mmu=svxx" string to obtain the current value of
virtual address usable bits [1]. Since this reflect the raw supported
MMU mode, it might differ from the logical one used internally which is
why arch_get_mmap_end() is used. Exporting the highest mmapable address
through hwprobe will allow a more stable interface to be used. For that
purpose, add a new hwprobe key named
RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS which will export the highest
userspace virtual address.
Link: https://github.com/openjdk/jdk/blob/master/src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp#L171 [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20240410144558.1104006-1-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Introduce the first flag for the hwprobe syscall. The flag basically
reverses its behavior, i.e. instead of populating the values of keys
for a given set of cpus, the set of cpus after the call is the result
of finding a set which supports the values of the keys. In order to
do this, we implement a pair compare function which takes the type of
value (a single value vs. a bitmask of booleans) into consideration.
We also implement vdso support for the new flag.
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20231122164700.127954-9-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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A hwprobe pair key is signed, but the hwprobe vDSO function was
only checking that the upper bound was valid. In order to help
avoid this type of problem in the future, and in anticipation of
this check becoming more complicated with sparse keys, introduce
and use a "key is valid" predicate function for the check.
Fixes: aa5af0aa90ba ("RISC-V: Add hwprobe vDSO function and data")
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20231010165101.14942-2-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Expose Zicboz through hwprobe and also provide a key to extract its
respective block size. Opportunistically add a macro and apply it to
current extensions in order to avoid duplicating code.
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230918131518.56803-11-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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This allows userspace to select various routines to use based on the
performance of misaligned access on the target hardware.
Rather than adding DT bindings, this change taps into the alternatives
mechanism used to probe CPU errata. Add a new function pointer alongside
the vendor-specific errata_patch_func() that probes for desirable errata
(otherwise known as "features"). Unlike the errata_patch_func(), this
function is called on each CPU as it comes up, so it can save
feature information per-CPU.
The T-head C906 has fast unaligned access, both as defined by GCC [1],
and in performing a basic benchmark, which determined that byte copies
are >50% slower than a misaligned word copy of the same data size (source
for this test at [2]):
bytecopy size f000 count 50000 offset 0 took 31664899 us
wordcopy size f000 count 50000 offset 0 took 5180919 us
wordcopy size f000 count 50000 offset 1 took 13416949 us
[1] https://github.com/gcc-mirror/gcc/blob/master/gcc/config/riscv/riscv.cc#L353
[2] https://pastebin.com/EPXvDHSW
Co-developed-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>
Link: https://lore.kernel.org/r/20230407231103.2622178-5-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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We have an implicit set of base behaviors that userspace depends on,
which are mostly defined in various ISA specifications.
Co-developed-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>
Link: https://lore.kernel.org/r/20230407231103.2622178-4-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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We don't have enough space for these all in ELF_HWCAP{,2} and there's no
system call that quite does this, so let's just provide an arch-specific
one to probe for hardware capabilities. This currently just provides
m{arch,imp,vendor}id, but with the key-value pairs we can pass more in
the future.
Co-developed-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>
Link: https://lore.kernel.org/r/20230407231103.2622178-3-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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