Re: [PATCH -fixes v4 3/3] riscv: Save/restore envcfg CSR during CPU suspend

On Tue, Feb 27, 2024 at 10:55:35PM -0800, Samuel Holland wrote:

The value of the [ms]envcfg CSR is lost when entering a nonretentive idle state, so the CSR must be rewritten when resuming the CPU.

Cc: stable@vger.kernel.org # v6.7+ Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode") Signed-off-by: Samuel Holland samuel.holland@sifive.com

---

Changes in v4:

• Check for Xlinuxenvcfg instead of Zicboz

Changes in v3:

• Check for Zicboz instead of the privileged ISA version

Changes in v2:

• Check for privileged ISA v1.12 instead of the specific CSR
• Use riscv_has_extension_likely() instead of new ALTERNATIVE()s

arch/riscv/include/asm/suspend.h | 1 + arch/riscv/kernel/suspend.c | 4 ++++ 2 files changed, 5 insertions(+)

diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h index 02f87867389a..491296a335d0 100644 --- a/arch/riscv/include/asm/suspend.h +++ b/arch/riscv/include/asm/suspend.h @@ -14,6 +14,7 @@ struct suspend_context { struct pt_regs regs; /* Saved and restored by high-level functions */ unsigned long scratch;

• unsigned long envcfg; unsigned long tvec; unsigned long ie;

#ifdef CONFIG_MMU diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c index 239509367e42..299795341e8a 100644 --- a/arch/riscv/kernel/suspend.c +++ b/arch/riscv/kernel/suspend.c @@ -15,6 +15,8 @@ void suspend_save_csrs(struct suspend_context *context) { context->scratch = csr_read(CSR_SCRATCH);

• if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))

• context->envcfg = csr_read(CSR_ENVCFG);
  

  context->tvec = csr_read(CSR_TVEC); context->ie = csr_read(CSR_IE);

@@ -36,6 +38,8 @@ void suspend_save_csrs(struct suspend_context *context) void suspend_restore_csrs(struct suspend_context *context) { csr_write(CSR_SCRATCH, context->scratch);

• if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))

• csr_write(CSR_ENVCFG, context->envcfg);
  

  csr_write(CSR_TVEC, context->tvec); csr_write(CSR_IE, context->ie);

2.43.1

Picking _likely vs. _unlikely sometimes feels like flipping a coin, but we'll presumably be increasing the likelihood of xlinuxenvcfg being present as we add more and more envcfg using extensions, so maybe we should use _likely here now, lest we forget to change it someday. But, either way,

Reviewed-by: Andrew Jones ajones@ventanamicro.com

Thanks, drew