Previously, we use alternative mechanism to dynamically patch
the CMO operations for THEAD C906/C910 during boot for performance
reason. But as pointed out by Arnd, "there is already a significant
cost in accessing the invalidated cache lines afterwards, which is
likely going to be much higher than the cost of an indirect branch".
And indeed, there's no performance difference with GMAC and EMMC per
my test on Sipeed Lichee Pi 4A board.
Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify
the alternative code, and to acchieve Arnd's goal -- "I think
moving the THEAD ops at the same level as all nonstandard operations
makes sense, but I'd still leave CMO as an explicit fast path that
avoids the indirect branch. This seems like the right thing to do both
for readability and for platforms on which the indirect branch has a
noticeable overhead."
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231114143338.2406-2-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
The CMO op macros initially used lower case, as the original iteration
of the ALT_CMO_OP alternative stringified the first parameter to
finalise the assembly for the standard variant.
As a knock-on, the T-Head versions of these CMOs had to use mixed case
defines. Commit dd23e95358 ("RISC-V: replace cbom instructions with
an insn-def") removed the asm construction with stringify, replacing it
an insn-def macro, rending the lower-case surplus to requirements.
As far as I can tell from a brief check, CBO_zero does not see similar
use and didn't require the mixed case define in the first place.
Replace the lower case characters now for consistency with other
insn-def macros in the standard and T-Head forms, and adjust the
callsites.
Suggested-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20230915-aloe-dollar-994937477776@spud
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
T-Head now maintains some specification for their extended instructions
at [1], in which all instructions are prefixed "th.".
Follow this practice in the kernel comments.
Link: https://github.com/T-head-Semi/thead-extension-spec [1]
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
The dcache.cva encoding shown in the comments are wrong, it's for
dcache.cval1 (which is restricted to L1) instead.
Fix this in the comment and in the hardcoded instruction.
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Tested-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Guo Ren <guoren@kernel.org>
Tested-by: Drew Fustini <dfustini@baylibre.com>
Link: https://lore.kernel.org/r/20230912072410.2481-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Add required ports of the Alternative scheme for Andes CPU cores.
I/O Coherence Port (IOCP) provides an AXI interface for connecting external
non-caching masters, such as DMA controllers. IOCP is a specification
option and is disabled on the Renesas RZ/Five SoC due to this reason cache
management needs a software workaround.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com> # tyre-kicking on a d1
Link: https://lore.kernel.org/r/20230818135723.80612-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Conor Dooley <conor@kernel.org> says:
From: Conor Dooley <conor.dooley@microchip.com>
I've yoinked patch 1 from Drew's series adding support for Zicboz &
attached two more patches here that remove the need for, and then drop
the toolchain support checks for Zicbom. The goal is to remove the need
for checking the presence of toolchain Zicbom support in the work being
done to support non instruction based CMOs [1].
I've tested compliation on a number of different configurations with
the Zicbom config option enabled. The important ones to call out I
guess are:
- clang/llvm 14 w/ LLVM=1 which doesn't support Zicbom atm.
- gcc 11 w/ binutils 2.37 which doesn't support Zicbom atm either.
- clang/llvm 15 w/ LLVM=1 BUT with binutils 2.37's ld. This is the
configuration that prompted adding the LD checks as cc/as supports
Zicbom, but ld doesn't [2].
- gcc 12 w/ binutils 2.39 & clang 15 w/ LLVM=1, both of these supported
Zicbom before and still do.
I also checked building the THEAD errata etc with
CONFIG_RISCV_ISA_ZICBOM disabled, and there were no build issues there
either.
* b4-shazam-merge:
RISC-V: remove toolchain version checks for Zicbom
RISC-V: replace cbom instructions with an insn-def
RISC-V: insn-def: Add I-type insn-def
Link: https://lore.kernel.org/r/20230108163356.3063839-1-conor@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Commit 4bf8860760 ("riscv: cpufeature: extend
riscv_cpufeature_patch_func to all ISA extensions") switched ISA
extension alternatives to use the RISCV_ISA_EXT_* macros instead of
CPUFEATURE_*. This was mismerged when applied on top of the Zbb series,
so the Zbb alternatives referenced the wrong errata ID values.
Fixes: 9daca9a5b9 ("Merge patch series "riscv: improve boot time isa extensions handling"")
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230212021534.59121-3-samuel@sholland.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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>
riscv_cpufeature_patch_func() currently only scans a limited set of
cpufeatures, explicitly defined with macros. Extend it to probe for all
ISA extensions.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230128172856.3814-5-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Add handling for ZBB extension and add support for using it as a
variant for optimized string functions.
Support for the Zbb-str-variants is limited to the GNU-assembler
for now, as LLVM has not yet acquired the functionality to
selectively change the arch option in assembler code.
This is still under review at
https://reviews.llvm.org/D123515
Co-developed-by: Christoph Muellner <christoph.muellner@vrull.eu>
Signed-off-by: Christoph Muellner <christoph.muellner@vrull.eu>
Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230113212301.3534711-3-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
With the T-HEAD C9XX cores being designed before or during the ratification
to the SSCOFPMF extension, it implements functionality very similar but
not equal to it.
It implements overflow handling and also some privilege-mode filtering.
While SSCOFPMF supports this for all modes, the C9XX only implements the
filtering for M-mode and S-mode but not user-mode.
So add some adaptions to allow the C9XX to still handle
its PMU through the regular SBI PMU interface instead of defining new
interfaces or drivers.
To work properly, this requires a matching change in SBI, though the actual
interface between kernel and SBI does not change.
The main differences are a the overflow CSR and irq number.
As the reading of the overflow-csr is in the hot-path during irq handling,
use an errata and alternatives to not introduce new conditionals there.
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/all/20221011231841.2951264-2-heiko@sntech.de/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This series is based on the alternatives changes done in my svpbmt
series and thus also depends on Atish's isa-extension parsing series.
It implements using the cache-management instructions from the Zicbom-
extension to handle cache flush, etc actions on platforms needing them.
SoCs using cpu cores from T-Head like the Allwinne D1 implement a
different set of cache instructions. But while they are different,
instructions they provide the same functionality, so a variant can easly
hook into the existing alternatives mechanism on those.
[Palmer: Some minor fixups, including a RISCV_ISA_ZICBOM dependency on
MMU that's probably not strictly necessary. The Zicbom support will
trip up sparse for users that have new toolchains, I just sent a patch.]
Link: https://lore.kernel.org/all/20220706231536.2041855-1-heiko@sntech.de/
Link: https://lore.kernel.org/linux-sparse/20220811033138.20676-1-palmer@rivosinc.com/T/#u
* palmer/riscv-zicbom:
riscv: implement cache-management errata for T-Head SoCs
riscv: Add support for non-coherent devices using zicbom extension
dt-bindings: riscv: document cbom-block-size
of: also handle dma-noncoherent in of_dma_is_coherent()
* Enabling the FPU is now a static_key.
* Improvements to the Svpbmt support.
* CPU topology bindings for a handful of systems.
* Support for systems with 64-bit hart IDs.
* Many settings have been enabled in the defconfig, including both
support for the StarFive systems and many of the Docker requirements.
There are also a handful of cleanups and improvements, like usual.
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Merge tag 'riscv-for-linus-5.20-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux
Pull RISC-V updates from Palmer Dabbelt:
- Enabling the FPU is now a static_key
- Improvements to the Svpbmt support
- CPU topology bindings for a handful of systems
- Support for systems with 64-bit hart IDs
- Many settings have been enabled in the defconfig, including both
support for the StarFive systems and many of the Docker requirements
There are also a handful of cleanups and improvements, as usual.
* tag 'riscv-for-linus-5.20-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (28 commits)
riscv: enable Docker requirements in defconfig
riscv: convert the t-head pbmt errata to use the __nops macro
riscv: introduce nops and __nops macros for NOP sequences
RISC-V: Add fast call path of crash_kexec()
riscv: mmap with PROT_WRITE but no PROT_READ is invalid
riscv/efi_stub: Add 64bit boot-hartid support on RV64
riscv: cpu: Add 64bit hartid support on RV64
riscv: smp: Add 64bit hartid support on RV64
riscv: spinwait: Fix hartid variable type
riscv: cpu_ops_sbi: Add 64bit hartid support on RV64
riscv: dts: sifive: "fix" pmic watchdog node name
riscv: dts: canaan: Add k210 topology information
riscv: dts: sifive: Add fu740 topology information
riscv: dts: sifive: Add fu540 topology information
riscv: dts: starfive: Add JH7100 CPU topology
RISC-V: Add CONFIG_{NON,}PORTABLE
riscv: config: enable SOC_STARFIVE in defconfig
riscv: dts: microchip: Add mpfs' topology information
riscv: Kconfig.socs: Add comments
riscv: Kconfig.erratas: Add comments
...
The T-Head C906 and C910 implement a scheme for handling
cache operations different from the generic Zicbom extension.
Add an errata for it next to the generic dma coherency ops.
Reviewed-by: Samuel Holland <samuel@sholland.org>
Tested-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220706231536.2041855-5-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
The Zicbom ISA-extension was ratified in november 2021
and introduces instructions for dcache invalidate, clean
and flush operations.
Implement cache management operations for non-coherent devices
based on them.
Of course not all cores will support this, so implement an
alternative-based mechanism that replaces empty instructions
with ones done around Zicbom instructions.
As discussed in previous versions, assume the platform
being coherent by default so that non-coherent devices need
to get marked accordingly by firmware.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20220706231536.2041855-4-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Instead of manually inserting the list of nops, use the recently
introduced __nops(n) macro to make everything more readable.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
After commit a35707c3d8 ("riscv: add memory-type errata for T-Head"),
builds with LLVM's integrated assembler fail like:
In file included from arch/riscv/kernel/asm-offsets.c:10:
In file included from ./include/linux/mm.h:29:
In file included from ./include/linux/pgtable.h:6:
In file included from ./arch/riscv/include/asm/pgtable.h:114:
./arch/riscv/include/asm/pgtable-64.h:210:2: error: invalid input constraint '0' in asm
ALT_THEAD_PMA(prot_val);
^
./arch/riscv/include/asm/errata_list.h:88:4: note: expanded from macro 'ALT_THEAD_PMA'
: "0"(_val), \
^
This was reported upstream to LLVM where Jessica pointed out a couple of
issues with the existing implementation of ALT_THEAD_PMA:
* t3 is modified but not listed in the clobbers list.
* "+r"(_val) marks _val as both an input and output of the asm but then
"0"(_val) marks _val as an input matching constraint, which does not
make much sense in this situation, as %1 is not actually used in the
asm and matching constraints are designed to be used for different
inputs that need to use the same register.
Drop the matching contraint and shift all the operands by one, as %1 is
unused, and mark t3 as clobbered. This resolves the build error and goes
not cause any problems with GNU as.
Fixes: a35707c3d8 ("riscv: add memory-type errata for T-Head")
Link: https://github.com/ClangBuiltLinux/linux/issues/1641
Link: https://github.com/llvm/llvm-project/issues/55514
Link: https://gcc.gnu.org/onlinedocs/gcc/Simple-Constraints.html
Suggested-by: Jessica Clarke <jrtc27@jrtc27.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220518184529.454008-1-nathan@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Some current cpus based on T-Head cores implement memory-types
way different than described in the svpbmt spec even going
so far as using PTE bits marked as reserved.
Add the T-Head vendor-id and necessary errata code to
replace the affected instructions.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20220511192921.2223629-13-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Svpbmt (the S should be capitalized) is the
"Supervisor-mode: page-based memory types" extension
that specifies attributes for cacheability, idempotency
and ordering.
The relevant settings are done in special bits in PTEs:
Here is the svpbmt PTE format:
| 63 | 62-61 | 60-8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
N MT RSW D A G U X W R V
^
Of the Reserved bits [63:54] in a leaf PTE, the high bit is already
allocated (as the N bit), so bits [62:61] are used as the MT (aka
MemType) field. This field specifies one of three memory types that
are close equivalents (or equivalent in effect) to the three main x86
and ARMv8 memory types - as shown in the following table.
RISC-V
Encoding &
MemType RISC-V Description
---------- ------------------------------------------------
00 - PMA Normal Cacheable, No change to implied PMA memory type
01 - NC Non-cacheable, idempotent, weakly-ordered Main Memory
10 - IO Non-cacheable, non-idempotent, strongly-ordered I/O memory
11 - Rsvd Reserved for future standard use
As the extension will not be present on all implementations,
implement a method to handle cpufeatures via alternatives
to not incur runtime penalties on cpu variants not supporting
specific extensions and patch relevant code parts at runtime.
Co-developed-by: Wei Fu <wefu@redhat.com>
Signed-off-by: Wei Fu <wefu@redhat.com>
Co-developed-by: Liu Shaohua <liush@allwinnertech.com>
Signed-off-by: Liu Shaohua <liush@allwinnertech.com>
Co-developed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Guo Ren <guoren@kernel.org>
[moved to use the alternatives mechanism]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-10-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
For certain SiFive CPUs, "sfence.vma addr" cannot exactly flush addr
from TLB in the particular cases. The details could be found here:
https://sifive.cdn.prismic.io/sifive/167a1a56-03f4-4615-a79e-b2a86153148f_FU740_errata_20210205.pdf
In order to ensure the functionality, this patch uses the Alternative
scheme to replace all "sfence.vma addr" with "sfence.vma" at runtime.
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Add sign extension to the $badaddr before addressing the instruction page
fault and instruction access fault to workaround the issue "cip-453".
To avoid affecting the existing code sequence, this patch will creates two
trampolines to add sign extension to the $badaddr. By the "alternative"
mechanism, these two trampolines will replace the original exception
handler of instruction page fault and instruction access fault in the
excp_vect_table. In this case, only the specific SiFive CPU core jumps to
the do_page_fault and do_trap_insn_fault through these two trampolines.
Other CPUs are not affected.
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Introduce the "alternative" mechanism from ARM64 and x86 to apply the CPU
vendors' errata solution at runtime. The main purpose of this patch is
to provide a framework. Therefore, the implementation is quite basic for
now so that some scenarios could not use this schemei, such as patching
code to a module, relocating the patching code and heterogeneous CPU
topology.
Users could use the macro ALTERNATIVE to apply an errata to the existing
code flow. In the macro ALTERNATIVE, users need to specify the manufacturer
information(vendorid, archid, and impid) for this errata. Therefore, kernel
will know this errata is suitable for which CPU core. During the booting
procedure, kernel will select the errata required by the CPU core and then
patch it. It means that the kernel only applies the errata to the specified
CPU core. In this case, the vendor's errata does not affect each other at
runtime. The above patching procedure only occurs during the booting phase,
so we only take the overhead of the "alternative" mechanism once.
This "alternative" mechanism is enabled by default to ensure that all
required errata will be applied. However, users can disable this feature by
the Kconfig "CONFIG_RISCV_ERRATA_ALTERNATIVE".
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
