Re: [PATCH] mmc: rpmb: do not force a retune before RPMB switch

[Adrian Hunter <adrian.hunter@intel.com>]

On 11/12/23 17:05, Jorge Ramirez-Ortiz, Foundries wrote:
> On 11/12/23 13:32:57, Adrian Hunter wrote:
>> On 11/12/23 13:06, Jorge Ramirez-Ortiz, Foundries wrote:
>>> On 11/12/23 12:25:19, Adrian Hunter wrote:
>>>> On 11/12/23 10:00, Jorge Ramirez-Ortiz, Foundries wrote:
>>>>> On 06/12/23 11:00:47, Jorge Ramirez-Ortiz, Foundries wrote:
>>>>>> On 06/12/23 07:02:43, Avri Altman wrote:
>>>>>>>>
>>>>>>>> On 4/12/23 17:01, Jorge Ramirez-Ortiz wrote:
>>>>>>>>> Requesting a retune before switching to the RPMB partition has been
>>>>>>>>> observed to cause CRC errors on the RPMB reads (-EILSEQ).
>>>>>>>>
>>>>>>>> There are still 2 concerns:
>>>>>>>> 1) We don't really know the root cause.  Have you determined if here are
>>>>>>>> CRC errors in the main partition also?
>>>>>>
>>>>>> right, and I don't disagree with that.
>>>>>>
>>>>>> As a test I created a 4GB file from /dev/random which I then copied
>>>>>> several times (dd if= ....)
>>>>>>
>>>>>> root@uz3cg-dwg-sec:/sys/kernel/debug/mmc0# cat err_stats
>>>>>> # Command Timeout Occurred:      0
>>>>>> # Command CRC Errors Occurred:   0
>>>>>> # Data Timeout Occurred:         0
>>>>>> # Data CRC Errors Occurred:      0
>>>>>> # Auto-Cmd Error Occurred:       0
>>>>>> # ADMA Error Occurred:   0
>>>>>> # Tuning Error Occurred:         0
>>>>>> # CMDQ RED Errors:       0
>>>>>> # CMDQ GCE Errors:       0
>>>>>> # CMDQ ICCE Errors:      0
>>>>>> # Request Timedout:      0
>>>>>> # CMDQ Request Timedout:         0
>>>>>> # ICE Config Errors:     0
>>>>>> # Controller Timedout errors:    0
>>>>>> # Unexpected IRQ errors:         0
>>>>>>
>>>>>> However as soon as I access RPMB and fails (it takes just a few tries) I see:
>>>>>>
>>>>>> I/TC: RPMB: Using generated key
>>>>>> [   86.902118] sdhci-arasan ff160000.mmc: __mmc_blk_ioctl_cmd: data error -84
>>>>>> E/TC:? 0
>>>>>> E/TC:? 0 TA panicked with code 0xffff0000
>>>>>> E/LD:  Status of TA 22250a54-0bf1-48fe-8002-7b20f1c9c9b1
>>>>>> E/LD:   arch: aarch64
>>>>>> E/LD:  region  0: va 0xc0004000 pa 0x7e200000 size 0x002000 flags rw-s (ldelf)
>>>>>> E/LD:  region  1: va 0xc0006000 pa 0x7e202000 size 0x008000 flags r-xs (ldelf)
>>>>>> E/LD:  region  2: va 0xc000e000 pa 0x7e20a000 size 0x001000 flags rw-s (ldelf)
>>>>>> E/LD:  region  3: va 0xc000f000 pa 0x7e20b000 size 0x004000 flags rw-s (ldelf)
>>>>>> E/LD:  region  4: va 0xc0013000 pa 0x7e20f000 size 0x001000 flags r--s
>>>>>> E/LD:  region  5: va 0xc0014000 pa 0x7e22c000 size 0x005000 flags rw-s (stack)
>>>>>> E/LD:  region  6: va 0xc0019000 pa 0x818ea9ba8 size 0x002000 flags rw-- (param)
>>>>>> E/LD:  region  7: va 0xc001b000 pa 0x818e97ba8 size 0x001000 flags rw-- (param)
>>>>>> E/LD:  region  8: va 0xc004f000 pa 0x00001000 size 0x014000 flags r-xs [0]
>>>>>> E/LD:  region  9: va 0xc0063000 pa 0x00015000 size 0x008000 flags rw-s [0]
>>>>>> E/LD:   [0] 22250a54-0bf1-48fe-8002-7b20f1c9c9b1 @ 0xc004f000
>>>>>> E/LD:  Call stack:
>>>>>> E/LD:   0xc0051a14
>>>>>> E/LD:   0xc004f31c
>>>>>> E/LD:   0xc0052d40
>>>>>> E/LD:   0xc004f624
>>>>>>
>>>>>> root@uz3cg-dwg-sec:/var/rootdirs/home/fio# cat /sys/kernel/debug/mmc0/err_stats
>>>>>> # Command Timeout Occurred:      0
>>>>>> # Command CRC Errors Occurred:   0
>>>>>> # Data Timeout Occurred:         0
>>>>>> # Data CRC Errors Occurred:      1
>>>>>> # Auto-Cmd Error Occurred:       0
>>>>>> # ADMA Error Occurred:   0
>>>>>> # Tuning Error Occurred:         0
>>>>>> # CMDQ RED Errors:       0
>>>>>> # CMDQ GCE Errors:       0
>>>>>> # CMDQ ICCE Errors:      0
>>>>>> # Request Timedout:      0
>>>>>> # CMDQ Request Timedout:         0
>>>>>> # ICE Config Errors:     0
>>>>>> # Controller Timedout errors:    0
>>>>>> # Unexpected IRQ errors:         0
>>>>>>
>>>>>>>> 2) Forcing this on everyone
>>>>>>>>
>>>>>>>> The original idea was that because re-tuning cannot be done in RPMB, the
>>>>>>>> need to re-rune in RPMB could be avoided by always re-tuning before
>>>>>>>> switching to RPMB and then switching straight back. IIRC re-tuning should
>>>>>>>> guarantee at least 4MB more I/O without issue.
>>>>>>> Performance is hardly an issue in the context of RPMB access -
>>>>>>> For most cases it’s a single frame.
>>>>>>
>>>>>> Yes, the security use case typically stores hashes, variables
>>>>>> (bootcount, upgrade_available, versions, that sort of thing) and
>>>>>> certificates in RPMB.
>>>>>>
>>>>>> Since you mentioned, I am seeing that tuning before switching to RPMB
>>>>>> has an impact on performance. As a practical test, just reading a 6 byte
>>>>>> variable incurs in 50ms penalty in kernel space due to the need to
>>>>>> retune 5 times. Not great since the request is coming from a Trusted
>>>>>> Application via OP-TEE through the supplicant meaning this TEE thread
>>>>>> (they are statically allocated CFG_NUM_THREADS) will be reserved for
>>>>>> quite a bit of time.
>>>>>>
>>>>>> Roughly:
>>>>>> TA --> OP-TEE (core) --> TEE-supplicant --> Kernel (>50ms) --> OP-TEE --> TA
>>>>>
>>>>> To add more detail to the timing above, when using RPMB, OP-TEE stores
>>>>> the secure filesystem on RPMB as well, so accessing one of the variables
>>>>> stored in the filesystem consists on a number (~5) of individual RPMB
>>>>> requests (each one forcing a retune, each retune taking around 10ms).
>>>>>
>>>>> BTW, I also tried delaying the timing between those consecutive retunes
>>>>> (up to 1 second), but the issue still persisted.
>>>>>
>>>>>>
>>>>>> Adrian, I couldn't find the original performance justification for
>>>>>> enabling this feature globally. At which point do you think it becomes
>>>>>> beneficial to retune before accessing RPMB?
>>>>>
>>>>> How should we proceed with this patch then? can it be merged as I
>>>>> proposed? should I rewrite it differently? not sure what is next
>>>>
>>>> It would be good to try to determine if the error happens when the
>>>> switch command comes immediately after tuning.  For example, add
>>>> a delay after tuning and see if that makes any difference. e.g.
>>>>
>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>>> index c79f73459915..6b168659282a 100644
>>>> --- a/drivers/mmc/host/sdhci.c
>>>> +++ b/drivers/mmc/host/sdhci.c
>>>> @@ -2867,8 +2867,10 @@ int __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
>>>>
>>>>  		ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>>>>  		if (!(ctrl & SDHCI_CTRL_EXEC_TUNING)) {
>>>> -			if (ctrl & SDHCI_CTRL_TUNED_CLK)
>>>> +			if (ctrl & SDHCI_CTRL_TUNED_CLK) {
>>>> +				msleep(10);
>>>>  				return 0; /* Success! */
>>>> +			}
>>>>  			break;
>>>>  		}
>>>>
>>>>
>>>
>>> Thanks Adrian.
>>>
>>> The issue sill triggers (in this case on the last but one access to
>>> retrieve the 6 byte variable).
>>>
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -2781,6 +2781,7 @@ static int __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
>>>          * Issue opcode repeatedly till Execute Tuning is set to 0 or the number
>>>          * of loops reaches tuning loop count.
>>>          */
>>> + printk(KERN_ERR "tune starts[loop %d]\n", host->tuning_loop_count);
>>>         for (i = 0; i < host->tuning_loop_count; i++) {
>>>                 u16 ctrl;
>>>
>>> @@ -2799,8 +2800,11 @@ static int __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
>>>
>>>                 ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>>>                 if (!(ctrl & SDHCI_CTRL_EXEC_TUNING)) {
>>> -                   if (ctrl & SDHCI_CTRL_TUNED_CLK)
>>> -                           return 0; /* Success! */
>>> +                 if (ctrl & SDHCI_CTRL_TUNED_CLK) {
>>> +                         printk(KERN_ERR "tune success[%d]\n", i);
>>> +                         msleep(10);
>>> +                         return 0; /* Success! */
>>> +                 }
>>>                         break;
>>>                 }
>>>
>>>
>>> [  164.919090] tune starts[loop 40]
>>> [  164.923152] tune success[39]
>>> [  164.952106] tune starts[loop 40]
>>> [  164.956611] tune success[39]
>>> [  165.084402] tune starts[loop 40]
>>> [  165.089350] tune success[39]
>>> [  165.116491] tune starts[loop 40]
>>> [  165.120806] tune success[39]
>>> [  165.145016] sdhci-arasan ff160000.mmc: __mmc_blk_ioctl_cmd: data error -84
>>> E/TC:? 0
>>> E/TC:? 0 TA panicked with code 0xffff0000
>>> E/LD:  Status of TA 22250a54-0bf1-48fe-8002-7b20f1c9c9b1
>>> E/LD:   arch: aarch64
>>> E/LD:  region  0: va 0xc0004000 pa 0x7e200000 size 0x002000 flags rw-s (ldelf)
>>> E/LD:  region  1: va 0xc0006000 pa 0x7e202000 size 0x008000 flags r-xs (ldelf)
>>> E/LD:  region  2: va 0xc000e000 pa 0x7e20a000 size 0x001000 flags rw-s (ldelf)
>>> E/LD:  region  3: va 0xc000f000 pa 0x7e20b000 size 0x004000 flags rw-s (ldelf)
>>> E/LD:  region  4: va 0xc0013000 pa 0x7e20f000 size 0x001000 flags r--s
>>> E/LD:  region  5: va 0xc0014000 pa 0x7e22c000 size 0x005000 flags rw-s (stack)
>>> E/LD:  region  6: va 0xc0019000 pa 0x818ac38e8 size 0x001000 flags rw-- (param)
>>> E/LD:  region  7: va 0xc001a000 pa 0x818ac36e8 size 0x001000 flags rw-- (param)
>>> E/LD:  region  8: va 0xc0022000 pa 0x00001000 size 0x014000 flags r-xs [0]
>>> E/LD:  region  9: va 0xc0036000 pa 0x00015000 size 0x008000 flags rw-s [0]
>>> E/LD:   [0] 22250a54-0bf1-48fe-8002-7b20f1c9c9b1 @ 0xc0022000
>>> E/LD:  Call stack:
>>> E/LD:   0xc0024e58
>>> E/LD:   0xc0022388
>>> E/LD:   0xc0025d40
>>> E/LD:   0xc0022624
>>> [  166.119598] tune starts[loop 40]
>>> [  166.125700] tune success[39]
>>
>> It might make a difference if there is another command before the
>> switch command, e.g. add a CMD13 (could keep the tune print to tell
>> that the CMD13 comes after re-tuning)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index 892e74e611a0..3265049f4132 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -875,6 +875,7 @@ static int mmc_blk_part_switch_pre(struct mmc_card *card,
>>  				   unsigned int part_type)
>>  {
>>  	int ret = 0;
>> +	u32 status;
>>
>>  	if (part_type == EXT_CSD_PART_CONFIG_ACC_RPMB) {
>>  		if (card->ext_csd.cmdq_en) {
>> @@ -883,6 +884,9 @@ static int mmc_blk_part_switch_pre(struct mmc_card *card,
>>  				return ret;
>>  		}
>>  		mmc_retune_pause(card->host);
>> +		ret = mmc_send_status(card, &status);
>> +		pr_info("%s: %s: status %#x, ret %d\n", mmc_hostname(card->host), __func__, status, ret);
>> +		ret = 0;
>>  	}
>>
>>  	return ret;
>>
>>
>>
>> And another thing to try is SDHCI_QUIRK2_TUNING_WORK_AROUND
>>
> 
> I run it in a loop with all the proposed changes and after 6 or 7 seconds the error triggered:
> 
> $ while true; do if ! read_rpmb variable ;then exit 0; fi; done
> [....]
> 
> 
> [  146.686482] ldts: mmc0: mmc_blk_part_switch_pre: status 0x900, ret 0
> [  146.699092] ldts: tune starts[loop 40]
> [  146.704032] ldts: tune success[39]
> [  146.726442] ldts: mmc0: mmc_blk_part_switch_pre: status 0x900, ret 0
> [  146.745891] ldts: tune starts[loop 40]
> [  146.750858] ldts: tune success[39]
> [  146.774506] ldts: mmc0: mmc_blk_part_switch_pre: status 0x900, ret 0
> [  146.787191] ldts: tune starts[loop 40]
> [  146.792087] ldts: tune success[39]
> [  146.814544] ldts: mmc0: mmc_blk_part_switch_pre: status 0x900, ret 0
> [  146.826383] ldts: tune starts[loop 40]
> [  146.830942] ldts: tune success[39]
> [  146.854500] ldts: mmc0: mmc_blk_part_switch_pre: status 0x900, ret 0
> [  146.863421] sdhci-arasan ff160000.mmc: __mmc_blk_ioctl_cmd: data error -84
> E/TC:? 0
> E/TC:? 0 TA panicked with code 0xffff0000
> E/LD:  Status of TA 22250a54-0bf1-48fe-8002-7b20f1c9c9b1
> E/LD:   arch: aarch64
> E/LD:  region  0: va 0xc0004000 pa 0x7e200000 size 0x002000 flags rw-s (ldelf)
> E/LD:  region  1: va 0xc0006000 pa 0x7e202000 size 0x008000 flags r-xs (ldelf)
> E/LD:  region  2: va 0xc000e000 pa 0x7e20a000 size 0x001000 flags rw-s (ldelf)
> E/LD:  region  3: va 0xc000f000 pa 0x7e20b000 size 0x004000 flags rw-s (ldelf)
> E/LD:  region  4: va 0xc0013000 pa 0x7e20f000 size 0x001000 flags r--s
> E/LD:  region  5: va 0xc0014000 pa 0x7e22c000 size 0x005000 flags rw-s (stack)
> E/LD:  region  6: va 0xc0019000 pa 0x818c17b48 size 0x001000 flags rw-- (param)
> E/LD:  region  7: va 0xc001a000 pa 0x818c17d48 size 0x001000 flags rw-- (param)
> E/LD:  region  8: va 0xc003c000 pa 0x00001000 size 0x014000 flags r-xs [0]
> E/LD:  region  9: va 0xc0050000 pa 0x00015000 size 0x008000 flags rw-s [0]
> E/LD:   [0] 22250a54-0bf1-48fe-8002-7b20f1c9c9b1 @ 0xc003c000
> E/LD:  Call stack:
> E/LD:   0xc003ea14
> E/LD:   0xc003c31c
> E/LD:   0xc003fd40


I sent a patch to add a re-tuning test to mmc_test.  It would be
interesting to try that too.

https://lore.kernel.org/linux-mmc/20231214090902.43628-1-adrian.hunter@intel.com/T/#u