Re: [PATCH 1/2 v8] resource: add the new I/O resource descriptor 'IORES_DESC_RESERVED'

["Lendacky, Thomas" <Thomas.Lendacky@amd.com>]

On 3/16/19 2:31 AM, lijiang wrote:
> 
> 
> 在 2018年12月05日 05:33, Lendacky, Thomas 写道:
>> On 11/29/2018 09:37 PM, Dave Young wrote:
>>> + more people
>>>
>>> On 11/29/18 at 04:09pm, Lianbo Jiang wrote:
>>>> When doing kexec_file_load, the first kernel needs to pass the e820
>>>> reserved ranges to the second kernel. But kernel can not exactly
>>>> match the e820 reserved ranges when walking through the iomem resources
>>>> with the descriptor 'IORES_DESC_NONE', because several e820 types(
>>>> e.g. E820_TYPE_RESERVED_KERN/E820_TYPE_RAM/E820_TYPE_UNUSABLE/E820
>>>> _TYPE_RESERVED) are converted to the descriptor 'IORES_DESC_NONE'. It
>>>> may pass these four types to the kdump kernel, that is not desired result.
>>>>
>>>> So, this patch adds a new I/O resource descriptor 'IORES_DESC_RESERVED'
>>>> for the iomem resources search interfaces. It is helpful to exactly
>>>> match the reserved resource ranges when walking through iomem resources.
>>>>
>>>> In addition, since the new descriptor 'IORES_DESC_RESERVED' is introduced,
>>>> these code originally related to the descriptor 'IORES_DESC_NONE' need to
>>>> be updated. Otherwise, it will be easily confused and also cause some
>>>> errors. Because the 'E820_TYPE_RESERVED' type is converted to the new
>>>> descriptor 'IORES_DESC_RESERVED' instead of 'IORES_DESC_NONE', it has been
>>>> changed.
>>>>
>>>> Suggested-by: Dave Young <dyoung@redhat.com>
>>>> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
>>>> ---
>>>>  arch/ia64/kernel/efi.c |  4 ++++
>>>>  arch/x86/kernel/e820.c |  2 +-
>>>>  arch/x86/mm/ioremap.c  | 13 ++++++++++++-
>>>>  include/linux/ioport.h |  1 +
>>>>  kernel/resource.c      |  6 +++---
>>>>  5 files changed, 21 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
>>>> index 8f106638913c..1841e9b4db30 100644
>>>> --- a/arch/ia64/kernel/efi.c
>>>> +++ b/arch/ia64/kernel/efi.c
>>>> @@ -1231,6 +1231,10 @@ efi_initialize_iomem_resources(struct resource *code_resource,
>>>>  				break;
>>>>  
>>>>  			case EFI_RESERVED_TYPE:
>>>> +				name = "reserved";
>>>
>>> Ingo updated X86 code to use "Reserved",  I think it would be good to do
>>> same for this case as well
>>>
>>>> +				desc = IORES_DESC_RESERVED;
>>>> +				break;
>>>> +
>>>>  			case EFI_RUNTIME_SERVICES_CODE:
>>>>  			case EFI_RUNTIME_SERVICES_DATA:
>>>>  			case EFI_ACPI_RECLAIM_MEMORY:
>>>
>>> Originally, above 3 are all "reserved", so probably they all should be
>>> IORES_DESC_RESERVED.
>>>
>>> Can any IA64 people to review this?
>>>
>>>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
>>>> index 50895c2f937d..57fafdafb860 100644
>>>> --- a/arch/x86/kernel/e820.c
>>>> +++ b/arch/x86/kernel/e820.c
>>>> @@ -1048,10 +1048,10 @@ static unsigned long __init e820_type_to_iores_desc(struct e820_entry *entry)
>>>>  	case E820_TYPE_NVS:		return IORES_DESC_ACPI_NV_STORAGE;
>>>>  	case E820_TYPE_PMEM:		return IORES_DESC_PERSISTENT_MEMORY;
>>>>  	case E820_TYPE_PRAM:		return IORES_DESC_PERSISTENT_MEMORY_LEGACY;
>>>> +	case E820_TYPE_RESERVED:	return IORES_DESC_RESERVED;
>>>>  	case E820_TYPE_RESERVED_KERN:	/* Fall-through: */
>>>>  	case E820_TYPE_RAM:		/* Fall-through: */
>>>>  	case E820_TYPE_UNUSABLE:	/* Fall-through: */
>>>> -	case E820_TYPE_RESERVED:	/* Fall-through: */
>>>>  	default:			return IORES_DESC_NONE;
>>>>  	}
>>>>  }
>>>> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
>>>> index 5378d10f1d31..fea2ef99415d 100644
>>>> --- a/arch/x86/mm/ioremap.c
>>>> +++ b/arch/x86/mm/ioremap.c
>>>> @@ -83,7 +83,18 @@ static bool __ioremap_check_ram(struct resource *res)
>>>>  
>>>>  static int __ioremap_check_desc_other(struct resource *res)
>>>>  {
>>>> -	return (res->desc != IORES_DESC_NONE);
>>>> +	/*
>>>> +	 * But now, the 'E820_TYPE_RESERVED' type is converted to the new
>>>> +	 * descriptor 'IORES_DESC_RESERVED' instead of 'IORES_DESC_NONE',
>>>> +	 * it has been changed. And the value of 'mem_flags.desc_other'
>>>> +	 * is equal to 'true' if we don't strengthen the condition in this
>>>> +	 * function, that is wrong. Because originally it is equal to
>>>> +	 * 'false' for the same reserved type.
>>>> +	 *
>>>> +	 * So, that would be nice to keep it the same as before.
>>>> +	 */
>>>> +	return ((res->desc != IORES_DESC_NONE) &&
>>>> +		(res->desc != IORES_DESC_RESERVED));
>>>>  }
>>>
>>> Added Tom since he added the check function.  Is it possible to only
>>> check explict valid desc types instead of exclude IORES_DESC_NONE?
>>
>> Sorry for the delay...
>>
>> The original intent of the check was to map most memory as encrypted under
>> SEV if it was marked with a specific descriptor, since it was likely to
>> not be MMIO. I tried converting most things that mapped memory to memremap
>> vs ioremap, but ACPI was one area that I left alone and this check catches
>> the mapping of the ACPI tables. I suppose it's possible to change this to
>> check just for IORES_DESC_ACPI_* values, but I would have to do some
>> testing.
> 
> Recently, i tested it according to your advice, here it is really checking for the
> 'IORES_DESC_ACPI_*' values.  If you agree to this change, i would add the following
> patch into this patch set and post them again.
> 
> [root@localhost linux]# git diff arch/x86/mm/ioremap.c
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 0029604af8a4..0e3ba620612d 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -83,7 +83,8 @@ static bool __ioremap_check_ram(struct resource *res)
>  
>  static int __ioremap_check_desc_other(struct resource *res)
>  {
> -       return (res->desc != IORES_DESC_NONE);
> +       return ((res->desc == IORES_DESC_ACPI_TABLES) ||
> +               (res->desc == IORES_DESC_ACPI_NV_STORAGE));

I'm not a big fan of this. I think you should leave it as the previous
check you had for IORES_DESC_NONE and IORES_DESC_RESERVED. There's no
telling what type of resources may be mapped in the future where this
will break.

Adding a nice comment here about how IORES_DESC_NONE originally was to
identify MMIO and reserved areas. Now IORES_DESC_RESERVED has been created
for the reserved areas so the check needs to be expanded so that these
areas aren't mapped encrypted when using ioremap.

Thanks,
Tom

>  }
> 
> 
> Thanks.
> Lianbo
> 
>>
>> Thanks,
>> Tom
>>
>>>
>>>>  
>>>>  static int __ioremap_res_check(struct resource *res, void *arg)
>>>> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
>>>> index da0ebaec25f0..6ed59de48bd5 100644
>>>> --- a/include/linux/ioport.h
>>>> +++ b/include/linux/ioport.h
>>>> @@ -133,6 +133,7 @@ enum {
>>>>  	IORES_DESC_PERSISTENT_MEMORY_LEGACY	= 5,
>>>>  	IORES_DESC_DEVICE_PRIVATE_MEMORY	= 6,
>>>>  	IORES_DESC_DEVICE_PUBLIC_MEMORY		= 7,
>>>> +	IORES_DESC_RESERVED			= 8,
>>>>  };
>>>>  
>>>>  /* helpers to define resources */
>>>> diff --git a/kernel/resource.c b/kernel/resource.c
>>>> index b0fbf685c77a..f34a632c4169 100644
>>>> --- a/kernel/resource.c
>>>> +++ b/kernel/resource.c
>>>> @@ -994,7 +994,7 @@ __reserve_region_with_split(struct resource *root, resource_size_t start,
>>>>  	res->start = start;
>>>>  	res->end = end;
>>>>  	res->flags = type | IORESOURCE_BUSY;
>>>> -	res->desc = IORES_DESC_NONE;
>>>> +	res->desc = IORES_DESC_RESERVED;
>>>>  
>>>>  	while (1) {
>>>>  
>>>> @@ -1029,7 +1029,7 @@ __reserve_region_with_split(struct resource *root, resource_size_t start,
>>>>  				next_res->start = conflict->end + 1;
>>>>  				next_res->end = end;
>>>>  				next_res->flags = type | IORESOURCE_BUSY;
>>>> -				next_res->desc = IORES_DESC_NONE;
>>>> +				next_res->desc = IORES_DESC_RESERVED;
>>>>  			}
>>>>  		} else {
>>>>  			res->start = conflict->end + 1;
>>>> @@ -1477,7 +1477,7 @@ static int __init reserve_setup(char *str)
>>>>  			res->start = io_start;
>>>>  			res->end = io_start + io_num - 1;
>>>>  			res->flags |= IORESOURCE_BUSY;
>>>> -			res->desc = IORES_DESC_NONE;
>>>> +			res->desc = IORES_DESC_RESERVED;
>>>>  			res->child = NULL;
>>>>  			if (request_resource(parent, res) == 0)
>>>>  				reserved = x+1;
>>>> -- 
>>>> 2.17.1
>>>>
>>>
>>>
>>> There are a lot of places call region_intersects which use DESC_NONE,
>>> I'm not sure if needed changes accordingly.  Cced Dan and Toshi.
>>>
>>>
>>> Thanks
>>> Dave
>>>