Re: [PATCH] x86: vendor reserved memory type

[Yinghai Lu <yinghai@kernel.org>]

H. Peter Anvin wrote:
> Yinghai, Huang, Paul: looks good to you [see patch at end]?  Anyone else
> we should have look at this?
> 
> 	-hpa
> 
> 
> Cliff Wickman wrote:
>>> There is no difference between that and E820_RESERVED, so there is no
>>> reason to distinguish them.  The semantics are exactly the same.
>> I thought a new type would be clearer, but if it would break an e820
>> standard I withdraw the idea.  All is good as long as the memory gets reserved.
> 
> We *could* add private types with negative numbers if we had to, but
> that means adding some infrastructure, and this doesn't seem justified
> for this case.  There is also a cost involved, since different types
> can't be range-merged.
> 
>>> The real problem is that this condition is too lenient:
>>>
>>>                 if (md->attribute & EFI_MEMORY_WB)
>>>                         e820_type = E820_RAM;
>>>                 else
>>>                         e820_type = E820_RESERVED;
>>>
>>> It really should be something like:
>>>
>>> 	switch (md->type) {
>>> 	case EFI_LOADER_CODE:
>>> 	case EFI_LOADER_DATA:
>>> 	case EFI_BOOT_SERVICES_CODE:
>>> 	case EFI_BOOT_SERVICES_DATA:
>>> 	case EFI_CONVENTIONAL_MEMORY:
>>>                 if (md->attribute & EFI_MEMORY_WB)
>>>                         e820_type = E820_RAM;
>>>                 else
>>>                         e820_type = E820_RESERVED;
>>> 		break;
>>> 	case EFI_ACPI_RECLAIM_MEMORY:
>>> 		e820_type = E820_ACPI;
>>> 		break;
>>> 	case EFI_ACPI_MEMORY_NVS:
>>> 		e820_type = E820_NVS;
>>> 		break;
>>> 	case EFI_UNUSABLE_MEMORY:
>>> 		e820_type = E820_UNUSUABLE;
>>> 		break;
>>> 	default:
>>> 		e820_type = E820_RESERVED;
>>> 		break;
>>> 	}
>> Okay. I buy that as more straightforward.
>>  
>>> Personally, it's not clear to me if this should do add any non-memory
>>> ranges, as the boot loader should have done that, but I guess in this
>>> particular case we have already horked out.
>>>
>>> Another problem is that the comment is wrong.  sanitize_e820_map() will
>>> coalesce adjacent entries, as it should.
>>>
>>> Finally, randomly definiting a standard value in E820 with new semantics
>>> isn't going to fly; it's likely to conflict with official allocations.
>>>
>>> 	-hpa
>> I propose to submit your code (basically) in the form of the below patch.
>> It works for me.   Does it look okay to you?
>>
>>
>>  
>> Subject: [PATCH] x86: efi/e820 table merge fix
>>
>> This patch causes all the EFI_RESERVED_TYPE memory reservations to be recorded
>> in the e820 table as type E820_RESERVED.
>>
>> Without this patch EFI_RESERVED_TYPE memory reservations may be
>> marked usable in the e820 table. There may be a collision between
>> kernel use and some reserver's use of this memory.
>>
>> (An example use of this functionality is the UV system, which
>>  will access extremely large areas of memory with a memory engine
>>  that allows a user to address beyond the processor's range.  Such
>>  areas are reserved in the EFI table by the BIOS.
>>  Some loaders have a restricted number of entries possible in the e820 table,
>>  hence the need to record the reservations in the unrestricted EFI table.)
>>
>> The call to do_add_efi_memmap() is only made if "add_efi_memmap" is specified
>> on the kernel command line.
>>
>> Diffed against 2.6.30-rc8
>>
>> Signed-off-by: Cliff Wickman <cpw@sgi.com>
>> ---
>>  arch/x86/kernel/efi.c |   31 ++++++++++++++++++++++++++++---
>>  1 file changed, 28 insertions(+), 3 deletions(-)
>>
>> Index: linux/arch/x86/kernel/efi.c
>> ===================================================================
>> --- linux.orig/arch/x86/kernel/efi.c
>> +++ linux/arch/x86/kernel/efi.c
>> @@ -240,10 +240,35 @@ static void __init do_add_efi_memmap(voi
>>  		unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
>>  		int e820_type;
>>  
>> -		if (md->attribute & EFI_MEMORY_WB)
>> -			e820_type = E820_RAM;
>> -		else
>> +		switch (md->type) {
>> +		case EFI_LOADER_CODE:
>> +		case EFI_LOADER_DATA:
>> +		case EFI_BOOT_SERVICES_CODE:
>> +		case EFI_BOOT_SERVICES_DATA:
>> +		case EFI_CONVENTIONAL_MEMORY:
>> +			if (md->attribute & EFI_MEMORY_WB)
>> +				e820_type = E820_RAM;
>> +			else
>> +				e820_type = E820_RESERVED;
>> +			break;
>> +		case EFI_ACPI_RECLAIM_MEMORY:
>> +			e820_type = E820_ACPI;
>> +			break;
>> +		case EFI_ACPI_MEMORY_NVS:
>> +			e820_type = E820_NVS;
>> +			break;
>> +		case EFI_UNUSABLE_MEMORY:
>> +			e820_type = E820_UNUSABLE;
>> +			break;
>> +		default:
>> +			/*
>> +			 * EFI_RESERVED_TYPE EFI_RUNTIME_SERVICES_CODE
>> +			 * EFI_RUNTIME_SERVICES_DATA EFI_MEMORY_MAPPED_IO
>> +			 * EFI_MEMORY_MAPPED_IO_PORT_SPACE EFI_PAL_CODE
>> +			 */
>>  			e820_type = E820_RESERVED;

then, if those entries are near TOML, and it is E820_RESERVED now, and it could not be directly mapped at first point.

but later efi_remap will direct map it if the size is too big for runtime service.

not sure others.

YH

>> +			break;
>> +		}
>>  		e820_add_region(start, size, e820_type);
>>  	}
>>  	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
>>