linux-kernel - Re: [PATCH 03/10] platform/x86/intel/ifs: Image loading for new generations

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Date:   Fri, 15 Sep 2023 10:20:52 -0700
From:   "Joseph, Jithu" <jithu.joseph@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC:     <hdegoede@...hat.com>, <markgross@...nel.org>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
        <rostedt@...dmis.org>, <ashok.raj@...el.com>,
        <tony.luck@...el.com>, <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <patches@...ts.linux.dev>,
        <ravi.v.shankar@...el.com>, <pengfei.xu@...el.com>
Subject: Re: [PATCH 03/10] platform/x86/intel/ifs: Image loading for new
 generations



On 9/15/2023 9:46 AM, Ilpo Järvinen wrote:
> On Wed, 13 Sep 2023, Jithu Joseph wrote:
> 
>> Scan image loading flow for newer IFS generations (1 and 2) are slightly
>> different from that of current generation (0). In newer schemes,
>> loading need not be done once for each socket as was done in gen0.
>>
>> Also the width of CHUNK related bitfields in SCAN_HASHES_STATUS MSR has
>> increased from 8 -> 16 bits. Similarly there are width differences
>> for CHUNK_AUTHENTICATION_STATUS too.
>>
>> Further the parameter to AUTHENTICATE_AND_COPY_CHUNK is passed
>> differently in newer generations.
>>
>> Signed-off-by: Jithu Joseph <jithu.joseph@...el.com>
>> Reviewed-by: Tony Luck <tony.luck@...el.com>
>> Tested-by: Pengfei Xu <pengfei.xu@...el.com>
>> ---
>>  drivers/platform/x86/intel/ifs/ifs.h  |  27 ++++++
>>  drivers/platform/x86/intel/ifs/load.c | 113 +++++++++++++++++++++++++-
>>  2 files changed, 138 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/platform/x86/intel/ifs/ifs.h b/drivers/platform/x86/intel/ifs/ifs.h
>> index d666aeed20fc..886dc74de57d 100644
>> --- a/drivers/platform/x86/intel/ifs/ifs.h
>> +++ b/drivers/platform/x86/intel/ifs/ifs.h
>> @@ -137,6 +137,8 @@
>>  #define MSR_CHUNKS_AUTHENTICATION_STATUS	0x000002c5
>>  #define MSR_ACTIVATE_SCAN			0x000002c6
>>  #define MSR_SCAN_STATUS				0x000002c7
>> +#define MSR_SAF_CTRL				0x000004f0
>> +
>>  #define SCAN_NOT_TESTED				0
>>  #define SCAN_TEST_PASS				1
>>  #define SCAN_TEST_FAIL				2
>> @@ -158,6 +160,19 @@ union ifs_scan_hashes_status {
>>  	};
>>  };
>>  
>> +union ifs_scan_hashes_status_gen2 {
>> +	u64	data;
>> +	struct {
>> +		u16	chunk_size;
>> +		u16	num_chunks;
>> +		u8	error_code;
>> +		u32	chunks_in_stride :9;
>> +		u32	rsvd		:2;
>> +		u32	max_core_limit	:12;
>> +		u32	valid		:1;
> 
> This doesn't look it would be guaranteed to provide the alignment you seem 
> to want for the fields.

To Quote Tony from an earlier response to a similar query[1]

"This driver is X86_64 specific (and it seems
incredibly unlikely that some other architecture will copy this h/w
interface so closely that they want to re-use this driver. There's an x86_64
ABI that says how bitfields in C are allocated."



[1] https://lore.kernel.org/lkml/SJ1PR11MB6083EBD2D2826E0A247AF242FCD19@SJ1PR11MB6083.namprd11.prod.outlook.com/

Agree to the rest of your comments ... will revise them as per your suggestion.

Jithu