Palmer Dabbelt 9daca9a5b9 Merge patch series "riscv: improve boot time isa extensions handling" ... Jisheng Zhang <jszhang@kernel.org> says: Generally, riscv ISA extensions are fixed for any specific hardware platform, so a hart's features won't change after booting, this chacteristic makes it straightforward to use a static branch to check a specific ISA extension is supported or not to optimize performance. However, some ISA extensions such as SVPBMT and ZICBOM are handled via. the alternative sequences. Basically, for ease of maintenance, we prefer to use static branches in C code, but recently, Samuel found that the static branch usage in cpu_relax() breaks building with CONFIG_CC_OPTIMIZE_FOR_SIZE[1]. As Samuel pointed out, "Having a static branch in cpu_relax() is problematic because that function is widely inlined, including in some quite complex functions like in the VDSO. A quick measurement shows this static branch is responsible by itself for around 40% of the jump table." Samuel's findings pointed out one of a few downsides of static branches usage in C code to handle ISA extensions detected at boot time: static branch's metadata in the __jump_table section, which is not discarded after ISA extensions are finalized, wastes some space. I want to try to solve the issue for all possible dynamic handling of ISA extensions at boot time. Inspired by Mark[2], this patch introduces riscv_has_extension_*() helpers, which work like static branches but are patched using alternatives, thus the metadata can be freed after patching. [1]https://lore.kernel.org/linux-riscv/20220922060958.44203-1-samuel@sholland.org/ [2]https://lore.kernel.org/linux-arm-kernel/20220912162210.3626215-8-mark.rutland@arm.com/ [3]https://lore.kernel.org/linux-riscv/20221130225614.1594256-1-heiko@sntech.de/ * b4-shazam-merge: riscv: remove riscv_isa_ext_keys[] array and related usage riscv: KVM: Switch has_svinval() to riscv_has_extension_unlikely() riscv: cpu_relax: switch to riscv_has_extension_likely() riscv: alternative: patch alternatives in the vDSO riscv: switch to relative alternative entries riscv: module: Add ADD16 and SUB16 rela types riscv: module: move find_section to module.h riscv: fpu: switch has_fpu() to riscv_has_extension_likely() riscv: introduce riscv_has_extension_[un]likely() riscv: cpufeature: extend riscv_cpufeature_patch_func to all ISA extensions riscv: hwcap: make ISA extension ids can be used in asm riscv: cpufeature: detect RISCV_ALTERNATIVES_EARLY_BOOT earlier riscv: move riscv_noncoherent_supported() out of ZICBOM probe Link: https://lore.kernel.org/r/20230128172856.3814-1-jszhang@kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>		2023-02-01 19:36:25 -08:00
..
boot	RISC-V: kbuild: convert all use of SOC_FOO to ARCH_FOO	2022-12-27 18:01:40 +00:00
configs	RISC-V Patches for the 6.2 Merge Window, Part 1	2022-12-14 15:23:49 -08:00
errata	riscv: switch to relative alternative entries	2023-01-31 23:29:41 -08:00
include	Merge patch series "riscv: improve boot time isa extensions handling"	2023-02-01 19:36:25 -08:00
kernel	Merge patch series "riscv: improve boot time isa extensions handling"	2023-02-01 19:36:25 -08:00
kvm	riscv: KVM: Switch has_svinval() to riscv_has_extension_unlikely()	2023-01-31 23:29:44 -08:00
lib	RISC-V: add zbb support to string functions	2023-01-31 11:43:24 -08:00
mm	RISC-V Patches for the 6.2 Merge Window, Part 1	2022-12-14 15:23:49 -08:00
net	riscv, bpf: Emit fixed-length instructions for BPF_PSEUDO_FUNC	2022-12-06 20:59:27 +01:00
purgatory	RISC-V: add infrastructure to allow different str* implementations	2023-01-31 11:43:23 -08:00
Kbuild	riscv: move errata/ and kvm/ builds to arch/riscv/Kbuild	2022-06-01 22:26:32 -07:00
Kconfig	RISC-V: add zbb support to string functions	2023-01-31 11:43:24 -08:00
Kconfig.debug	RISC-V: Remove EARLY_PRINTK support	2018-12-17 10:23:46 -08:00
Kconfig.erratas	drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores	2022-10-27 14:35:20 -07:00
Kconfig.socs	RISC-V: Kconfig: Remove trailing whitespace	2023-01-24 18:09:12 -08:00
Makefile	RISC-V: kbuild: convert all use of SOC_FOO to ARCH_FOO	2022-12-27 18:01:40 +00:00