Re: [PATCH v10 18/21] ARM64 / ACPI: Select ACPI_REDUCED_HARDWARE_ONLY if ACPI is enabled on ARM64

[Hanjun Guo]

On 2015å03æ13æ 19:04, Lorenzo Pieralisi wrote:
> On Fri, Mar 13, 2015 at 03:28:45AM +0000, Hanjun Guo wrote:
>
> [...]
>
> > >   /*
> > >    * acpi_boot_table_init() called from setup_arch(), always.
> > >    *	1. find RSDP and get its address, and then find XSDT
> > >    *	2. extract all tables and checksums them all
> > >    *	3. check ACPI FADT revision
> > > + *	4. check ACPI FADT HW reduced flag
> > >    *
> > >    * We can parse ACPI boot-time tables such as MADT after
> > >    * this function is called.
> > >    */
> > >   void __init acpi_boot_table_init(void)
> > >   {
> > > +	struct acpi_table_header *table;
> > > +	struct acpi_table_fadt *fadt;
> > > +	acpi_status status;
> > > +	acpi_size tbl_size;
> > > +
> > >   	/*
> > >   	 * Enable ACPI instead of device tree unless
> > >   	 * - ACPI has been disabled explicitly (acpi=off), or
> > > @@ -351,19 +318,52 @@ void __init acpi_boot_table_init(void)
> > >   	    (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
> > >   		return;
> > >
> > > -	enable_acpi();
> > > -
> > >   	/* Initialize the ACPI boot-time table parser. */
> > >   	if (acpi_table_init()) {
> >
> > Since we disable ACPI in default, it is a bit strange for me to init all
> > the ACPI tables and parse FADT when ACPI is disabled, could you
> > put some comments here to clarify the purpose? other than that, it is looks
> > good to me.
>
> Ok, the purpose was to make things simpler, but I think that given
> current code it is not 100% safe to init ACPI tables with
> acpi_disabled == 1.
>
> To me having to enable ACPI to parse the tables and check *if* ACPI tables
> are there is a bit crazy, but I agree with you that given current code
> it is safer.
>
> Patch rewritten, here below, please have a look, test it and rework
> bits as needed, I added comments where I thought they were needed but
> please add to that if you feel it is worth it.
>
> It should be easy to split, let me know if you want an incremental
> version.

This one is much better, pretty fine to me, thanks!

I assume that this patch is cleanup patch on top of ARM64 ACPI
core patches, right?

Thanks
Hanjun

> Thanks !
> Lorenzo
>
> ---
>   arch/arm64/kernel/acpi.c | 103 +++++++++++++++++++++++++++++++----------------
>   1 file changed, 69 insertions(+), 34 deletions(-)
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 5819ef7..e5ee4d4 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -291,43 +291,60 @@ void acpi_unregister_gsi(u32 gsi)
>   }
>   EXPORT_SYMBOL_GPL(acpi_unregister_gsi);
>
> -static int __init acpi_parse_fadt(struct acpi_table_header *table)
> +/*
> + * acpi_fadt_sanity_check() - Check FADT presence and carry out sanity
> + *			      checks on it
> + *
> + * Return 0 on success,  <0 on failure
> + */
> +static int __init acpi_fadt_sanity_check(void)
>   {
> -	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
> +	struct acpi_table_header *table;
> +	struct acpi_table_fadt *fadt;
> +	acpi_status status;
> +	acpi_size tbl_size;
> +	int ret = 0;
> +
> +	/*
> +	 * FADT is required on arm64; retrieve it to check its presence
> +	 * and carry out revision and ACPI HW reduced compliancy tests
> +	 */
> +	status = acpi_get_table_with_size(ACPI_SIG_FADT, 0, &table, &tbl_size);
> +	if (ACPI_FAILURE(status)) {
> +		const char *msg = acpi_format_exception(status);
> +
> +		pr_err("Failed to get FADT table, %s\n", msg);
> +		return -ENODEV;
> +	}
> +
> +	fadt = (struct acpi_table_fadt *)table;
>
>   	/*
>   	 * Revision in table header is the FADT Major revision, and there
>   	 * is a minor revision of FADT which was introduced by ACPI 5.1,
>   	 * we only deal with ACPI 5.1 or newer revision to get GIC and SMP
> -	 * boot protocol configuration data, or we will disable ACPI.
> +	 * boot protocol configuration data.
>   	 */
> -	if (table->revision > 5 ||
> -	    (table->revision == 5 && fadt->minor_revision >= 1)) {
> -		if (!acpi_gbl_reduced_hardware) {
> -			pr_err("Not hardware reduced ACPI mode, will not be supported\n");
> -			goto disable_acpi;
> -		}
> -
> -		/*
> -		 * ACPI 5.1 only has two explicit methods to boot up SMP,
> -		 * PSCI and Parking protocol, but the Parking protocol is
> -		 * only specified for ARMv7 now, so make PSCI as the only
> -		 * way for the SMP boot protocol before some updates for
> -		 * the Parking protocol spec.
> -		 */
> -		if (acpi_psci_present())
> -			return 0;
> -
> -		pr_warn("No PSCI support, will not bring up secondary CPUs\n");
> -		return -EOPNOTSUPP;
> +	if (table->revision < 5 ||
> +	   (table->revision == 5 && fadt->minor_revision < 1)) {
> +		pr_err("Unsupported FADT revision %d.%d, should be 5.1+\n",
> +		       table->revision, fadt->minor_revision);
> +		ret = -EINVAL;
> +		goto out;
>   	}
>
> -	pr_warn("Unsupported FADT revision %d.%d, should be 5.1+, will disable ACPI\n",
> -		table->revision, fadt->minor_revision);
> +	if (!(fadt->flags & ACPI_FADT_HW_REDUCED)) {
> +		pr_err("FADT not ACPI hardware reduced compliant\n");
> +		ret = -EINVAL;
> +	}
>
> -disable_acpi:
> -	disable_acpi();
> -	return -EINVAL;
> +out:
> +	/*
> +	 * acpi_get_table_with_size() creates FADT table mapping that
> +	 * should be released after parsing and before resuming boot
> +	 */
> +	early_acpi_os_unmap_memory((char *)table, tbl_size);
> +	return ret;
>   }
>
>   /*
> @@ -335,12 +352,17 @@ disable_acpi:
>    *	1. find RSDP and get its address, and then find XSDT
>    *	2. extract all tables and checksums them all
>    *	3. check ACPI FADT revision
> + *	4. check ACPI FADT HW reduced flag
>    *
>    * We can parse ACPI boot-time tables such as MADT after
>    * this function is called.
> + *
> + * ACPI is enabled on return if ACPI tables initialized and sanity checks
> + * passed, disabled otherwise
>    */
>   void __init acpi_boot_table_init(void)
>   {
> +
>   	/*
>   	 * Enable ACPI instead of device tree unless
>   	 * - ACPI has been disabled explicitly (acpi=off), or
> @@ -351,19 +373,32 @@ void __init acpi_boot_table_init(void)
>   	    (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
>   		return;
>
> +	/*
> +	 * ACPI is disabled at this point. Enable it in order to parse
> +	 * the ACPI tables and carry out sanity checks
> +	 */
>   	enable_acpi();
>
>   	/* Initialize the ACPI boot-time table parser. */
>   	if (acpi_table_init()) {
> -		disable_acpi();
> -		return;
> +		pr_err("Failed to init ACPI tables\n");
> +		goto init_failed;
>   	}
>
> -	if (acpi_table_parse(ACPI_SIG_FADT, acpi_parse_fadt)) {
> -		/* disable ACPI if no FADT is found */
> -		disable_acpi();
> -		pr_err("Can't find FADT\n");
> -	}
> +	/*
> +	 * Check FADT presence and carry out FADT sanity checks
> +	 */
> +	if (acpi_fadt_sanity_check() < 0)
> +		goto init_failed;
> +
> +	/*
> +	 * ACPI tables initialized and FADT sanity checks passed, leave
> +	 * ACPI enabled and carry on booting
> +	 */
> +	return;
> +
> +init_failed:
> +	disable_acpi();
>   }
>
>   void __init acpi_gic_init(void)
--
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