Date:   Wed, 16 Jan 2019 23:24:13 +0100
From:   "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:     Dave Young <dyoung@...hat.com>, Kairui Song <kasong@...hat.com>
Cc:     Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, Baoquan He <bhe@...hat.com>,
        kexec@...ts.infradead.org, akpm@...ux-foundation.org,
        robert.moore@...el.com, erik.schmauss@...el.com,
        Len Brown <lenb@...nel.org>,
        Chao Fan <fanc.fnst@...fujitsu.com>
Subject: Re: [PATCH v2 2/2] x86, kexec_file_load: make it work with
 efi=noruntime or efi=old_map

On 1/16/2019 7:51 AM, Dave Young wrote:
> On 01/16/19 at 01:09pm, Kairui Song wrote:
>> On Wed, Jan 16, 2019 at 11:32 AM Dave Young <dyoung@...hat.com> wrote:
>>> On 01/16/19 at 12:10am, Borislav Petkov wrote:
>>>> On Tue, Jan 15, 2019 at 05:58:34PM +0800, Kairui Song wrote:
>>>>> When efi=noruntime or efi=oldmap is used, EFI services won't be available
>>>>> in the second kernel, therefore the second kernel will not be able to get
>>>>> the ACPI RSDP address from firmware by calling EFI services and won't
>>>>> boot. Previously we are expecting the user to set the acpi_rsdp=<addr>
>>>>> on kernel command line for second kernel as there was no way to pass RSDP
>>>>> address to second kernel.
>>>>>
>>>>> After commit e6e094e053af ('x86/acpi, x86/boot: Take RSDP address from
>>>>> boot params if available'), now it's possible to set an acpi_rsdp_addr
>>>>> parameter in the boot_params passed to second kernel, this commit make
>>>>> use of it, detect and set the RSDP address when it's required for second
>>>>> kernel to boot.
>>>>>
>>>>> Tested with an EFI enabled KVM VM with efi=noruntime.
>>>>>
>>>>> Suggested-by: Dave Young <dyoung@...hat.com>
>>>>> Signed-off-by: Kairui Song <kasong@...hat.com>
>>>>> ---
>>>>>   arch/x86/kernel/kexec-bzimage64.c | 21 +++++++++++++++++++++
>>>>>   drivers/acpi/acpica/tbxfroot.c    |  3 +--
>>>>>   include/acpi/acpixf.h             |  2 +-
>>>>>   3 files changed, 23 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
>>>>> index 53917a3ebf94..0a90dcbd041f 100644
>>>>> --- a/arch/x86/kernel/kexec-bzimage64.c
>>>>> +++ b/arch/x86/kernel/kexec-bzimage64.c
>>>>> @@ -20,6 +20,7 @@
>>>>>   #include <linux/mm.h>
>>>>>   #include <linux/efi.h>
>>>>>   #include <linux/verification.h>
>>>>> +#include <linux/acpi.h>
>>>>>
>>>>>   #include <asm/bootparam.h>
>>>>>   #include <asm/setup.h>
>>>>> @@ -255,8 +256,28 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
>>>>>      /* Setup EFI state */
>>>>>      setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
>>>>>                      efi_setup_data_offset);
>>>>> +
>>>>> +#ifdef CONFIG_ACPI
>>>>> +   /* Setup ACPI RSDP pointer in case EFI is not available in second kernel */
>>>>> +   if (!acpi_disabled && (!efi_enabled(EFI_RUNTIME_SERVICES) || efi_enabled(EFI_OLD_MEMMAP))) {
>>>>> +           /* Copied from acpi_os_get_root_pointer accordingly */
>>>>> +           params->acpi_rsdp_addr = boot_params.acpi_rsdp_addr;
>>>>> +           if (!params->acpi_rsdp_addr) {
>>>>> +                   if (efi_enabled(EFI_CONFIG_TABLES)) {
>>>>> +                           if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
>>>>> +                                   params->acpi_rsdp_addr = efi.acpi20;
>>>>> +                           else if (efi.acpi != EFI_INVALID_TABLE_ADDR)
>>>>> +                                   params->acpi_rsdp_addr = efi.acpi;
>>>>> +                   } else if (IS_ENABLED(CONFIG_ACPI_LEGACY_TABLES_LOOKUP)) {
>>>>> +                           acpi_find_root_pointer(&params->acpi_rsdp_addr);
>>>>> +                   }
>>>>> +           }
>>>>> +           if (!params->acpi_rsdp_addr)
>>>>> +                   pr_warn("RSDP is not available for second kernel\n");
>>>>> +   }
>>>>>   #endif
>>>> Amazing the amount of ACPI RDSP parsing and fiddling patches flying
>>>> around these days...
>>>>
>>>> In any case, this needs to be synchronized with:
>>>>
>>>> https://lkml.kernel.org/r/20190107032243.25324-1-fanc.fnst@cn.fujitsu.com
>>>>
>>>> and checked whether the above can be used instead of sprinkling of ACPI
>>>> parsing code left and right.
>>> Both Baoquan and Chao are cced for comments.
>>> The above KASLR patches seems some early code to parsing acpi, but I think in this
>>> patch just call acpi function to get the root pointer no need to add the
>>> duplicate logic of if/else/else if.
>>>
>>> Kairui,  do you have any reason for the checking?  Is there some simple
>>> acpi function to just return the root pointer?
>> Hi, I'm afraid that would require moving multiple structure and
>> function out of .init,
>> acpi_os_get_root_pointer is an ideal function to do the job, but it's
>> in .init and (on x86) it will call x86_init.acpi.get_root_pointer (by
>> calling acpi_arch_get_root_pointer) which will also be freed after
>> init, unless I change the x86_init, move they out of .init which is
>> not a good idea.
>>
>> Maybe I could split acpi_os_get_root_pointer into two, one gets freed
>> after init, one for later use. But the "acpi_rsdp_addr" trick only
>> works for x86, and this would change more common acpi driver code so
>> not sure if a good idea.
> Can the acpi root pointer be saved after initialized? If that is good
> then a new function to get it would be easier. But need opinion from
> acpi people.

For that, please repost the series with a CC to linux-acpi@...r.kernel.org.

Thanks!

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