[PATCH v8 09/21] ARM64 / ACPI: Disable ACPI if FADT revision is less than 5.1

Lorenzo Pieralisi
2015-02-04T13:06:26Z

On Wed, Feb 04, 2015 at 09:38:25AM +0000, Hanjun Guo wrote:
> On 2015?02?04? 01:20, Catalin Marinas wrote:
> > On Mon, Feb 02, 2015 at 12:45:37PM +0000, Hanjun Guo wrote:
> >> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> >> index afe10b4..b9f64ec 100644
> >> --- a/arch/arm64/kernel/acpi.c
> >> +++ b/arch/arm64/kernel/acpi.c
> >> @@ -13,6 +13,8 @@
> >> * published by the Free Software Foundation.
> >> */
> >>
> >> +#define pr_fmt(fmt) "ACPI: " fmt
> >> +
> >> #include <linux/acpi.h>
> >> #include <linux/bootmem.h>
> >> #include <linux/cpumask.h>
> >> @@ -49,10 +51,32 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
> >> early_memunmap(map, size);
> >> }
> >>
> >> +static int __init acpi_parse_fadt(struct acpi_table_header *table)
> >> +{
> >> + struct acpi_table_fadt *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.
> >> + */
> >> + if (table->revision > 5 ||
> >> + (table->revision == 5 && fadt->minor_revision >= 1))
> >> + return 0;
> >> +
> >> + pr_warn("Unsupported FADT revision %d.%d, should be 5.1+, will disable ACPI\n",
> >> + table->revision, fadt->minor_revision);
> >> + disable_acpi();
> >> +
> >> + return -EINVAL;
> >> +}
> >> +
> >> /*
> >> * 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
> >> *
> >> * We can parse ACPI boot-time tables such as MADT after
> >> * this function is called.
> >> @@ -64,8 +88,16 @@ void __init acpi_boot_table_init(void)
> >> return;
> >>
> >> /* Initialize the ACPI boot-time table parser. */
> >> - if (acpi_table_init())
> >> + if (acpi_table_init()) {
> >> + disable_acpi();
> >> + return;
> >> + }
> >> +
> >> + 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");
> >> + }
> >> }
> >
> > It looks fine to call disable_acpi() here but a bit weird to call it
> > again in acpi_parse_fadt(). I guess that's because acpi_table_parse()
> > ignores the return value of the handler() call. I think it's better to
> > fix the core code (can be an additional patch on top of this series).
>
> I checked all the code calling acpi_table_parse() and I found that it
> will be no functional change if we return the value of handler(), but
> I need Rafael's confirm on it.

Are you sure ? All calls to acpi_table_parse() that checks the return
value are affected. I guess that depends on what an error return from
the handler means, from acpi_table_parse():

* Return 0 if table found, -errno if not.

So, if table is found but parsing fails that acpi_table_parse()
signature should be changed if the handler barfs with an error and
it is propagated. Still, I share Catalin's comment.

Have you thought about getting the FADT through:

acpi_get_table_with_size()

and check the revision there instead of going through acpi_table_parse()
for that ?

I wonder if the revision information is not already available without
needing to retrieve the FADT again.

On top of that, this patch should be squashed, I have a feeling that
between patch 4 and 9, there is a window where ACPI versions predating
5.1 are ok on arm64, which is not the case. I do not think that's a
bisectable issue, but keep this in mind please.

Thanks,
Lorenzo