linux-kernel - Re: [Xen-devel] [PATCH 2/3] x86/acpi: take rsdp address for boot params if available

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Date:   Tue, 28 Nov 2017 10:18:34 +0000
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     Juergen Gross <jgross@...e.com>
CC:     <linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>,
        <x86@...nel.org>, <corbet@....net>, <rjw@...ysocki.net>,
        <linux-acpi@...r.kernel.org>, <mingo@...hat.com>, <hpa@...or.com>,
        <boris.ostrovsky@...cle.com>, <tglx@...utronix.de>,
        <lenb@...nel.org>
Subject: Re: [Xen-devel] [PATCH 2/3] x86/acpi: take rsdp address for boot
 params if available

On Tue, Nov 28, 2017 at 10:43:59AM +0100, Juergen Gross wrote:
> In case the rsdp address in struct boot_params is specified don't try
> to find the table by searching, but take the address directly as set
> by the boot loader.
> 
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  drivers/acpi/osl.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 3bb46cb24a99..3b25e2ad7d75 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -45,6 +45,10 @@
>  #include <linux/uaccess.h>
>  #include <linux/io-64-nonatomic-lo-hi.h>
>  
> +#ifdef CONFIG_X86
> +#include <asm/setup.h>
> +#endif
> +
>  #include "internal.h"
>  
>  #define _COMPONENT		ACPI_OS_SERVICES
> @@ -195,6 +199,10 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
>  	if (acpi_rsdp)
>  		return acpi_rsdp;
>  #endif
> +#ifdef CONFIG_X86
> +	if (boot_params.hdr.acpi_rsdp_addr)
> +		return boot_params.hdr.acpi_rsdp_addr;
> +#endif

I'm struggling to figure out how was PVH getting the RSDP previously,
because that should be removed now that it's in the zero-page.

Roger.