From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Anup Patel <anup@brainfault.org>, Atish Patra <atishp@atishpatra.org>, Heiko Stuebner <heiko@sntech.de>, Conor Dooley <conor.dooley@microchip.com>, Andrew Jones <ajones@ventanamicro.com> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org Subject: [PATCH v4 00/13] riscv: improve boot time isa extensions handling Date: Sun, 15 Jan 2023 23:49:40 +0800 [thread overview] Message-ID: <20230115154953.831-1-jszhang@kernel.org> (raw) 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. Since v3 - collect Reviewed-by tag and remove Heiko's reviewed-by from patch5 - address Conor and Andrew comments - fix two building errors of !MMU and RV32 Since v2 - rebase on riscv-next - collect Reviewed-by tag - fix jal imm construction - combine Heiko's code and my code for jal patching, thus add Co-developed-by tag - address comments from Conor Since v1 - rebase on v6.1-rc7 + Heiko's alternative improvements[3] - collect Reviewed-by tag - add one patch to update jal offsets in patched alternatives - add one patch to switch to relative alternative entries - add patches to patch vdso [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/ Andrew Jones (1): riscv: KVM: Switch has_svinval() to riscv_has_extension_unlikely() Jisheng Zhang (12): riscv: fix jal offsets in patched alternatives riscv: move riscv_noncoherent_supported() out of ZICBOM probe riscv: cpufeature: detect RISCV_ALTERNATIVES_EARLY_BOOT earlier riscv: hwcap: make ISA extension ids can be used in asm riscv: cpufeature: extend riscv_cpufeature_patch_func to all ISA extensions riscv: introduce riscv_has_extension_[un]likely() riscv: fpu: switch has_fpu() to riscv_has_extension_likely() riscv: module: move find_section to module.h riscv: switch to relative alternative entries riscv: alternative: patch alternatives in the vDSO riscv: cpu_relax: switch to riscv_has_extension_likely() riscv: remove riscv_isa_ext_keys[] array and related usage arch/riscv/errata/sifive/errata.c | 3 +- arch/riscv/errata/thead/errata.c | 11 ++- arch/riscv/include/asm/alternative-macros.h | 20 ++--- arch/riscv/include/asm/alternative.h | 17 ++-- arch/riscv/include/asm/errata_list.h | 9 +- arch/riscv/include/asm/hwcap.h | 97 +++++++++++---------- arch/riscv/include/asm/insn.h | 27 ++++++ arch/riscv/include/asm/module.h | 16 ++++ arch/riscv/include/asm/switch_to.h | 3 +- arch/riscv/include/asm/vdso.h | 4 + arch/riscv/include/asm/vdso/processor.h | 2 +- arch/riscv/kernel/alternative.c | 56 ++++++++++++ arch/riscv/kernel/cpufeature.c | 78 +++-------------- arch/riscv/kernel/module.c | 15 ---- arch/riscv/kernel/setup.c | 3 + arch/riscv/kernel/vdso.c | 5 -- arch/riscv/kernel/vdso/vdso.lds.S | 7 ++ arch/riscv/kvm/tlb.c | 3 +- 18 files changed, 214 insertions(+), 162 deletions(-) -- 2.38.1
WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Anup Patel <anup@brainfault.org>, Atish Patra <atishp@atishpatra.org>, Heiko Stuebner <heiko@sntech.de>, Conor Dooley <conor.dooley@microchip.com>, Andrew Jones <ajones@ventanamicro.com> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org Subject: [PATCH v4 00/13] riscv: improve boot time isa extensions handling Date: Sun, 15 Jan 2023 23:49:40 +0800 [thread overview] Message-ID: <20230115154953.831-1-jszhang@kernel.org> (raw) 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. Since v3 - collect Reviewed-by tag and remove Heiko's reviewed-by from patch5 - address Conor and Andrew comments - fix two building errors of !MMU and RV32 Since v2 - rebase on riscv-next - collect Reviewed-by tag - fix jal imm construction - combine Heiko's code and my code for jal patching, thus add Co-developed-by tag - address comments from Conor Since v1 - rebase on v6.1-rc7 + Heiko's alternative improvements[3] - collect Reviewed-by tag - add one patch to update jal offsets in patched alternatives - add one patch to switch to relative alternative entries - add patches to patch vdso [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/ Andrew Jones (1): riscv: KVM: Switch has_svinval() to riscv_has_extension_unlikely() Jisheng Zhang (12): riscv: fix jal offsets in patched alternatives riscv: move riscv_noncoherent_supported() out of ZICBOM probe riscv: cpufeature: detect RISCV_ALTERNATIVES_EARLY_BOOT earlier riscv: hwcap: make ISA extension ids can be used in asm riscv: cpufeature: extend riscv_cpufeature_patch_func to all ISA extensions riscv: introduce riscv_has_extension_[un]likely() riscv: fpu: switch has_fpu() to riscv_has_extension_likely() riscv: module: move find_section to module.h riscv: switch to relative alternative entries riscv: alternative: patch alternatives in the vDSO riscv: cpu_relax: switch to riscv_has_extension_likely() riscv: remove riscv_isa_ext_keys[] array and related usage arch/riscv/errata/sifive/errata.c | 3 +- arch/riscv/errata/thead/errata.c | 11 ++- arch/riscv/include/asm/alternative-macros.h | 20 ++--- arch/riscv/include/asm/alternative.h | 17 ++-- arch/riscv/include/asm/errata_list.h | 9 +- arch/riscv/include/asm/hwcap.h | 97 +++++++++++---------- arch/riscv/include/asm/insn.h | 27 ++++++ arch/riscv/include/asm/module.h | 16 ++++ arch/riscv/include/asm/switch_to.h | 3 +- arch/riscv/include/asm/vdso.h | 4 + arch/riscv/include/asm/vdso/processor.h | 2 +- arch/riscv/kernel/alternative.c | 56 ++++++++++++ arch/riscv/kernel/cpufeature.c | 78 +++-------------- arch/riscv/kernel/module.c | 15 ---- arch/riscv/kernel/setup.c | 3 + arch/riscv/kernel/vdso.c | 5 -- arch/riscv/kernel/vdso/vdso.lds.S | 7 ++ arch/riscv/kvm/tlb.c | 3 +- 18 files changed, 214 insertions(+), 162 deletions(-) -- 2.38.1 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next reply other threads:[~2023-01-15 16:00 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-01-15 15:49 Jisheng Zhang [this message] 2023-01-15 15:49 ` [PATCH v4 00/13] riscv: improve boot time isa extensions handling Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 01/13] riscv: fix jal offsets in patched alternatives Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 02/13] riscv: move riscv_noncoherent_supported() out of ZICBOM probe Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 03/13] riscv: cpufeature: detect RISCV_ALTERNATIVES_EARLY_BOOT earlier Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 04/13] riscv: hwcap: make ISA extension ids can be used in asm Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 05/13] riscv: cpufeature: extend riscv_cpufeature_patch_func to all ISA extensions Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-18 22:28 ` Conor Dooley 2023-01-18 22:28 ` Conor Dooley 2023-01-15 15:49 ` [PATCH v4 06/13] riscv: introduce riscv_has_extension_[un]likely() Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 16:29 ` Conor Dooley 2023-01-15 16:29 ` Conor Dooley 2023-01-18 22:18 ` Conor Dooley 2023-01-18 22:18 ` Conor Dooley 2023-01-15 15:49 ` [PATCH v4 07/13] riscv: fpu: switch has_fpu() to riscv_has_extension_likely() Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 08/13] riscv: module: move find_section to module.h Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 09/13] riscv: switch to relative alternative entries Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-18 22:11 ` Conor Dooley 2023-01-18 22:11 ` Conor Dooley 2023-01-20 18:34 ` Andrew Jones 2023-01-20 18:34 ` Andrew Jones 2023-01-26 7:09 ` Andrew Jones 2023-01-26 7:09 ` Andrew Jones 2023-01-28 16:43 ` Jisheng Zhang 2023-01-28 16:43 ` Jisheng Zhang 2023-01-26 19:33 ` Conor Dooley 2023-01-26 19:33 ` Conor Dooley 2023-01-15 15:49 ` [PATCH v4 10/13] riscv: alternative: patch alternatives in the vDSO Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 11/13] riscv: cpu_relax: switch to riscv_has_extension_likely() Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-15 15:49 ` [PATCH v4 12/13] riscv: KVM: Switch has_svinval() to riscv_has_extension_unlikely() Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-27 3:51 ` Anup Patel 2023-01-27 3:51 ` Anup Patel 2023-01-15 15:49 ` [PATCH v4 13/13] riscv: remove riscv_isa_ext_keys[] array and related usage Jisheng Zhang 2023-01-15 15:49 ` Jisheng Zhang 2023-01-25 3:50 ` [PATCH v4 00/13] riscv: improve boot time isa extensions handling patchwork-bot+linux-riscv 2023-01-25 3:50 ` patchwork-bot+linux-riscv
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