linux-kernel - Re: [PATCH] ALSA: emu10k1: Stop using iommu

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Message-ID: <e1dc64d3-d5b3-07f1-5fd6-c132fc247bb6@arm.com>
Date:   Tue, 5 Apr 2022 13:37:19 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     perex@...ex.cz, tiwai@...e.com, iommu@...ts.linux-foundation.org,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: emu10k1: Stop using iommu_present()

On 2022-04-05 13:29, Takashi Iwai wrote:
> On Tue, 05 Apr 2022 14:13:33 +0200,
> Robin Murphy wrote:
>>
>> iommu_get_domain_for_dev() is already perfectly happy to return NULL
>> if the given device has no IOMMU. Drop the unnecessary check.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@....com>
> 
> This will change the code behavior.  The current code does nothing if
> no IOMMU is found, but after your removal of the check, the code
> reaches to emu->iommu_workaround = true incorrectly.

Ah, right you are - I should have looked more closely at the second 
check, where of course "domain &&" wants tweaking to "!domain ||" as 
well. I'll send a v2 in a bit...

Thanks,
Robin.

> 
> 
> thanks,
> 
> Takashi
> 
>> ---
>>   sound/pci/emu10k1/emu10k1_main.c | 3 ---
>>   1 file changed, 3 deletions(-)
>>
>> diff --git a/sound/pci/emu10k1/emu10k1_main.c b/sound/pci/emu10k1/emu10k1_main.c
>> index 86cc1ca025e4..5ffab343b89c 100644
>> --- a/sound/pci/emu10k1/emu10k1_main.c
>> +++ b/sound/pci/emu10k1/emu10k1_main.c
>> @@ -1751,9 +1751,6 @@ static void snd_emu10k1_detect_iommu(struct snd_emu10k1 *emu)
>>   
>>   	emu->iommu_workaround = false;
>>   
>> -	if (!iommu_present(emu->card->dev->bus))
>> -		return;
>> -
>>   	domain = iommu_get_domain_for_dev(emu->card->dev);
>>   	if (domain && domain->type == IOMMU_DOMAIN_IDENTITY)
>>   		return;
>> -- 
>> 2.28.0.dirty
>>