Re: [Qemu-devel] [SeaBIOS] [PATCH v2 4/5] acpi: load and link tables from /etc/acpi/

[Kevin O'Connor <kevin@koconnor.net>]

On Sun, Jul 07, 2013 at 06:42:43PM +0300, Michael S. Tsirkin wrote:
> Load files in /etc/acpi/, link them using
> a linker script and use for acpi tables, including the RSDP.
> Presense of RSDP in this directory completely disables
> generating and loading legacy acpi tables.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  src/acpi.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/src/acpi.c b/src/acpi.c
> index a81f0cb..07d311a 100644
> --- a/src/acpi.c
> +++ b/src/acpi.c
> @@ -27,6 +27,7 @@
>  #include "config.h" // CONFIG_*
>  #include "paravirt.h" // RamSize
>  #include "dev-q35.h"
> +#include "linker.h"
>  
>  #include "acpi-dsdt.hex"
>  
> @@ -599,6 +600,34 @@ static const struct pci_device_id acpi_find_tbl[] = {
>  
>  struct rsdp_descriptor *RsdpAddr;
>  
> +/* Look for RSDP signature in files loaded in FSEG */
> +struct rsdp_descriptor *
> +acpi_find_rsdp_rom(void)
> +{
> +    struct romfile_s *file = NULL;
> +    struct rsdp_descriptor *rsdp = NULL;
> +    for (;;) {
> +        file = romfile_findprefix("", file);
> +        if (!file)
> +            break;
> +
> +        if (!file->data || !pmm_test_fseg(file->data) ||
> +            file->size < sizeof(rsdp->signature))
> +            continue;
> +
> +        void *data;
> +
> +        for (data = file->data;
> +             data + sizeof(*rsdp) <= file->data + file->size;
> +             data++) {
> +            rsdp = data;
> +            if (rsdp->signature == cpu_to_le64(RSDP_SIGNATURE))
> +                return rsdp;
> +        }
> +    }
> +    return NULL;
> +}
> +
>  #define MAX_ACPI_TABLES 20
>  void
>  acpi_setup(void)
> @@ -608,6 +637,16 @@ acpi_setup(void)
>  
>      dprintf(3, "init ACPI tables\n");
>  
> +    linker_loader_execute("/etc/linker-script");
> +
> +    RsdpAddr = acpi_find_rsdp_rom();
> +
> +    if (RsdpAddr) {
> +        return;
> +    }

I don't understand this.  Why not use the presence of
"/etc/linker-script" to determine if ACPI should be produced.

Also, /etc/linker-script is not very informative - how about something
like "/etc/biostables".

-Kevin