On Wed, Feb 14, 2024 at 01:01:57AM -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.

The [ms]envcfg CSR was added in version 1.12 of the privileged ISA, and is used by extensions other than Zicboz. However, the kernel currenly has no way to determine the privileged ISA version. Since Zicboz is the only in-kernel user of this CSR so far, use it as a proxy for determining if the CSR is implemented.

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 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..28166006688e 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_ZICBOZ))

• 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_ZICBOZ))

• csr_write(CSR_ENVCFG, context->envcfg);
  

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

2.43.0

Reviewed-by: Andrew Jones ajones@ventanamicro.com