Re: [PATCH v8 00/11] Add support for SBI v0.2 and CPU hotplug

From: Palmer Dabbelt
Date: Wed Feb 19 2020 - 16:48:56 EST


On Tue, 11 Feb 2020 17:48:11 PST (-0800), Atish Patra wrote:
The Supervisor Binary Interface(SBI) specification[1] now defines a
base extension that provides extendability to add future extensions
while maintaining backward compatibility with previous versions.
The new version is defined as 0.2 and older version is marked as 0.1.

This series adds support v0.2 and a unified calling convention
implementation between 0.1 and 0.2. It also add other SBI v0.2
functionality defined in [2]. The base support for SBI v0.2 is already
available in OpenSBI v0.5. It also adds SBI HSM extension and cpu-hotplug
support for RISC-V which requires additional patches[3] in OpenSBI.

Now that 0.2-rc1 has been tagged we should really start to get this into shape
to merge this. My biggest worry is being able to put together a kernel that
can boot on both 0.1 and 0.2 SBIs, with the hart lottery being my major worry
there. I just skimmed this, but I was expected to see something like
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 271860fc2c3f..849ba75959ba 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -187,6 +187,7 @@ relocate:
la a3, .Lsecondary_park
csrw CSR_TVEC, a3
+#ifdef CONFIG_SBI_V01
slli a3, a0, LGREG
la a1, __cpu_up_stack_pointer
la a2, __cpu_up_task_pointer
@@ -212,7 +213,10 @@ relocate:
#endif
tail smp_callin
-#endif
+#else /* !CONFIG_SBI_V01 */
+ pr_warn("multiple harts booted an SBI v0.2+ only kernel");
+#endif /* CONFIG_SBI_V01 */
+#endif /* CONFIG_SMP */
END(_start)

but I don't. Is there something else doing this?

[1] https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.adoc
[2] https://github.com/riscv/riscv-sbi-doc/pull/27
[3] http://lists.infradead.org/pipermail/opensbi/2020-January/001050.html

The patches are also available in following github repositery.

OpenSBI : https://github.com/atishp04/opensbi/tree/sbi_hsm_v1
Linux Kernel: https://github.com/atishp04/linux/tree/sbi_v0.2_v8

Changes from v7->v8:
1. Refactored to code to have modular cpu_ops calls.
2. Refactored HSM extension from sbi.c to cpu_ops_sbi.c.
3. Fix plic driver to handle cpu hotplug.

Changes from v6->v7:
1. Rebased on v5.5
2. Fixed few compilation issues for !CONFIG_SMP and !CONFIG_RISCV_SBI
3. Added SBI HSM extension
4. Add CPU hotplug support

Changes from v5->v6
1. Fixed few compilation issues around config.
2. Fixed hart mask generation issues for RFENCE & IPI extensions.

Changes from v4->v5
1. Fixed few minor comments related to static & inline.
2. Make sure that every patch is boot tested individually.

Changes from v3->v4.
1. Rebased on for-next.
2. Fixed issuses with checkpatch --strict.
3. Unfied all IPI/fence related functions.
4. Added Hfence related SBI calls.

Changes from v2->v3.
1. Moved v0.1 extensions to a new config.
2. Added support for relacement extensions of v0.1 extensions.

Changes from v1->v2
1. Removed the legacy calling convention.
2. Moved all SBI related calls to sbi.c.
3. Moved all SBI related macros to uapi.

Atish Patra (11):
RISC-V: Mark existing SBI as 0.1 SBI.
RISC-V: Add basic support for SBI v0.2
RISC-V: Add SBI v0.2 extension definitions
RISC-V: Introduce a new config for SBI v0.1
RISC-V: Implement new SBI v0.2 extensions
RISC-V: Move relocate and few other functions out of __init
RISC-V: Add cpu_ops and modify default booting method
RISC-V: Add SBI HSM extension
RISC-V: Add supported for ordered booting method using HSM
irqchip/sifive-plic: Initialize the plic handler when cpu comes online
RISC-V: Support cpu hotplug

arch/riscv/Kconfig | 19 +-
arch/riscv/include/asm/cpu_ops.h | 46 +++
arch/riscv/include/asm/sbi.h | 194 ++++++----
arch/riscv/include/asm/smp.h | 24 ++
arch/riscv/kernel/Makefile | 6 +
arch/riscv/kernel/cpu-hotplug.c | 87 +++++
arch/riscv/kernel/cpu_ops.c | 48 +++
arch/riscv/kernel/cpu_ops_sbi.c | 113 ++++++
arch/riscv/kernel/cpu_ops_spinwait.c | 42 +++
arch/riscv/kernel/head.S | 179 +++++----
arch/riscv/kernel/sbi.c | 524 ++++++++++++++++++++++++++-
arch/riscv/kernel/setup.c | 24 +-
arch/riscv/kernel/smpboot.c | 56 +--
arch/riscv/kernel/traps.c | 2 +-
arch/riscv/kernel/vmlinux.lds.S | 5 +-
drivers/irqchip/irq-sifive-plic.c | 34 +-
include/linux/cpuhotplug.h | 1 +
17 files changed, 1227 insertions(+), 177 deletions(-)
create mode 100644 arch/riscv/include/asm/cpu_ops.h
create mode 100644 arch/riscv/kernel/cpu-hotplug.c
create mode 100644 arch/riscv/kernel/cpu_ops.c
create mode 100644 arch/riscv/kernel/cpu_ops_sbi.c
create mode 100644 arch/riscv/kernel/cpu_ops_spinwait.c