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@xxxxxxxxxxxxxxx> # v6.7+
> Fixes: 43c16d51a19b ("RISC-V: Enable cbo.zero in usermode")
> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
> ---
>
> 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@xxxxxxxxxxxxxxxx>
