Re: [Xen-devel] [PATCH][v2] xen: Pass the location of the ACPI RSDP to DOM0.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.01.14 at 23:08, Philip Wernersbach <philip.wernersbach@xxxxxxxxx> 
>>> wrote:
> xen: [v2] Pass the location of the ACPI RSDP to DOM0.
> 
> Some machines, such as recent IBM servers, only allow the OS to get the
> ACPI RSDP from EFI. Since Xen nukes DOM0's ability to access EFI, DOM0

This reads as if this was a bug in Xen, which it isn't. Dom0's
lack of EFI support when running on top of Xen is the issue.

> cannot get the RSDP on these machines, leading to all sorts of
> functionality reductions.
> 
> Signed-off-by: Philip Wernersbach <philip.wernersbach@xxxxxxxxx>
> 
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index b49256d..8c307c9 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1378,6 +1378,25 @@ void __init __start_xen(unsigned long mbi_p)
>              safe_strcat(dom0_cmdline, " acpi=");
>              safe_strcat(dom0_cmdline, acpi_param);
>          }
> +        if ( !strstr(dom0_cmdline, "acpi_rsdp=") )

I think I had indicated my opposition to this sort of hack on v1
already; I'm not sure I asked which OSes usable as Dom0 but
other than Linux recognize this option. Or which versions of
Linux actually do (I'm pretty sure older ones don't).

Bottom line - I continue to think that the issue should be fixed
in Linux.

> +        {
> +            char acpi_os_root_pointer_string[MAX_RSDP_ADDRESS_STRING];
> +            int acpi_os_root_pointer_string_size =
> snprintf(acpi_os_root_pointer_string,
> +
> MAX_RSDP_ADDRESS_STRING, "%08lX",
> +
> acpi_os_get_root_pointer());
> +
> +            if ( (acpi_os_root_pointer_string_size > 0) &&
> (acpi_os_root_pointer_string_size <= MAX_RSDP_ADDRESS_STRING) )
> +            {
> +                safe_strcat(dom0_cmdline, " acpi_rsdp=0x");
> +                safe_strcat(dom0_cmdline, acpi_os_root_pointer_string);
> +            }
> +            else
> +            {
> +                printk(XENLOG_WARNING "RSDP Address String Size Check
> Failed!\n");
> +                printk(XENLOG_WARNING "Not passing acpi_rsdp to Dom0!\n");
> +                printk(XENLOG_WARNING "(Expected size 1-%d, got
> %d)\n", MAX_RSDP_ADDRESS_STRING, acpi_os_root_pointer_string_size);
> +            }
> +        }
> 
>          cmdline = dom0_cmdline;
>      }
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index 8c5697e..a7c3905 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -750,6 +750,7 @@ struct start_info {
>                                  /*  SIF_MOD_START_PFN set in flags).      
> */
>      unsigned long mod_len;      /* Size (bytes) of pre-loaded module.     */
>  #define MAX_GUEST_CMDLINE 1024
> +#define MAX_RSDP_ADDRESS_STRING 21

This clearly doesn't belong here (public header). In fact it doesn't
belong into any header at all, as it's being used only in a single
source file.

Jan

>      int8_t cmd_line[MAX_GUEST_CMDLINE];
>      /* The pfn range here covers both page table and p->m table frames.   */
>      unsigned long first_p2m_pfn;/* 1st pfn forming initial P->M table.    */




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