| Message ID | 20220421170354.10555-1-palmer@rivosinc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v1] RISC-V: Only default to spinwait on SBI-0.1 and M-mode | expand |
On Thu, Apr 21, 2022 at 10:05 AM Palmer Dabbelt <palmer@rivosinc.com> wrote: > > From: Palmer Dabbelt <palmer@rivosinc.com> > > The spinwait boot method has been superseeded by the SBI HSM extension > for some time now, but it still enabled by default. This causes some > issues on large hart count systems, which will hang if a physical hart > exists that is larger than NR_CPUS. > > Users on modern SBI implemenation don't need spinwait, and while it's > probably possible to deal with some of the spinwait issues let's just > restrict the default to systems that are likely to actually use it. > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > --- > This seems to be the source of many of my new hangs when trying to test > the NR_CPUS=512 support. It's not really related, just fallout from > testing different setups. > --- > arch/riscv/Kconfig | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 00fd9c548f26..dd5e975abe37 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -359,7 +359,7 @@ config RISCV_SBI_V01 > config RISCV_BOOT_SPINWAIT > bool "Spinwait booting method" > depends on SMP > - default y > + default y if RISCV_SBI_V01 || RISCV_M_MODE > help > This enables support for booting Linux via spinwait method. In the > spinwait method, all cores randomly jump to Linux. One of the cores > @@ -370,6 +370,12 @@ config RISCV_BOOT_SPINWAIT > rely on ordered booting via SBI HSM extension which gets chosen > dynamically at runtime if the firmware supports it. > > + Since spinwait is incompatible with sparse hart IDs, it requires > + NR_CPUS be large enough to contain the physical hart ID of the first > + hart to enter Linux. > + > + If unsure what to do here, say N. > + > config KEXEC > bool "Kexec system call" > select KEXEC_CORE > -- > 2.34.1 > Reviewed-by: Atish Patra <atishp@rivosinc.com>
On Thu, Apr 21, 2022 at 10:35 PM Palmer Dabbelt <palmer@rivosinc.com> wrote: > > From: Palmer Dabbelt <palmer@rivosinc.com> > > The spinwait boot method has been superseeded by the SBI HSM extension > for some time now, but it still enabled by default. This causes some > issues on large hart count systems, which will hang if a physical hart > exists that is larger than NR_CPUS. > > Users on modern SBI implemenation don't need spinwait, and while it's > probably possible to deal with some of the spinwait issues let's just > restrict the default to systems that are likely to actually use it. > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> Looks good to me. Reviewed-by: Anup Patel <anup@brainfault.org> Regards, Anup > --- > This seems to be the source of many of my new hangs when trying to test > the NR_CPUS=512 support. It's not really related, just fallout from > testing different setups. > --- > arch/riscv/Kconfig | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 00fd9c548f26..dd5e975abe37 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -359,7 +359,7 @@ config RISCV_SBI_V01 > config RISCV_BOOT_SPINWAIT > bool "Spinwait booting method" > depends on SMP > - default y > + default y if RISCV_SBI_V01 || RISCV_M_MODE > help > This enables support for booting Linux via spinwait method. In the > spinwait method, all cores randomly jump to Linux. One of the cores > @@ -370,6 +370,12 @@ config RISCV_BOOT_SPINWAIT > rely on ordered booting via SBI HSM extension which gets chosen > dynamically at runtime if the firmware supports it. > > + Since spinwait is incompatible with sparse hart IDs, it requires > + NR_CPUS be large enough to contain the physical hart ID of the first > + hart to enter Linux. > + > + If unsure what to do here, say N. > + > config KEXEC > bool "Kexec system call" > select KEXEC_CORE > -- > 2.34.1 >
On Thu, 21 Apr 2022 10:03:55 PDT (-0700), Palmer Dabbelt wrote: > From: Palmer Dabbelt <palmer@rivosinc.com> > > The spinwait boot method has been superseeded by the SBI HSM extension > for some time now, but it still enabled by default. This causes some > issues on large hart count systems, which will hang if a physical hart > exists that is larger than NR_CPUS. > > Users on modern SBI implemenation don't need spinwait, and while it's > probably possible to deal with some of the spinwait issues let's just > restrict the default to systems that are likely to actually use it. > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > --- > This seems to be the source of many of my new hangs when trying to test > the NR_CPUS=512 support. It's not really related, just fallout from > testing different setups. > --- > arch/riscv/Kconfig | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 00fd9c548f26..dd5e975abe37 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -359,7 +359,7 @@ config RISCV_SBI_V01 > config RISCV_BOOT_SPINWAIT > bool "Spinwait booting method" > depends on SMP > - default y > + default y if RISCV_SBI_V01 || RISCV_M_MODE > help > This enables support for booting Linux via spinwait method. In the > spinwait method, all cores randomly jump to Linux. One of the cores > @@ -370,6 +370,12 @@ config RISCV_BOOT_SPINWAIT > rely on ordered booting via SBI HSM extension which gets chosen > dynamically at runtime if the firmware supports it. > > + Since spinwait is incompatible with sparse hart IDs, it requires > + NR_CPUS be large enough to contain the physical hart ID of the first > + hart to enter Linux. > + > + If unsure what to do here, say N. > + > config KEXEC > bool "Kexec system call" > select KEXEC_CORE This is on for-next, with some typos fixed.
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 00fd9c548f26..dd5e975abe37 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -359,7 +359,7 @@ config RISCV_SBI_V01 config RISCV_BOOT_SPINWAIT bool "Spinwait booting method" depends on SMP - default y + default y if RISCV_SBI_V01 || RISCV_M_MODE help This enables support for booting Linux via spinwait method. In the spinwait method, all cores randomly jump to Linux. One of the cores @@ -370,6 +370,12 @@ config RISCV_BOOT_SPINWAIT rely on ordered booting via SBI HSM extension which gets chosen dynamically at runtime if the firmware supports it. + Since spinwait is incompatible with sparse hart IDs, it requires + NR_CPUS be large enough to contain the physical hart ID of the first + hart to enter Linux. + + If unsure what to do here, say N. + config KEXEC bool "Kexec system call" select KEXEC_CORE