linux-kernel - Re: [RFC v3 05/10] iommu: Do not map reserved regions

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Date:   Wed, 7 Dec 2016 16:15:08 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Robin Murphy <robin.murphy@....com>, eric.auger.pro@...il.com,
        christoffer.dall@...aro.org, marc.zyngier@....com,
        alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
        tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org
Cc:     drjones@...hat.com, kvm@...r.kernel.org, punit.agrawal@....com,
        linux-kernel@...r.kernel.org, diana.craciun@....com,
        iommu@...ts.linux-foundation.org, pranav.sawargaonkar@...il.com
Subject: Re: [RFC v3 05/10] iommu: Do not map reserved regions

Hi Robin

On 06/12/2016 18:36, Robin Murphy wrote:
> On 15/11/16 13:09, Eric Auger wrote:
>> As we introduced IOMMU_RESV_NOMAP and IOMMU_RESV_MSI regions,
>> let's prevent those new regions from being mapped.
>>
>> Signed-off-by: Eric Auger <eric.auger@...hat.com>
>> ---
>>  drivers/iommu/iommu.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 6ee529f..a4530ad 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -343,6 +343,9 @@ static int iommu_group_create_direct_mappings(struct iommu_group *group,
>>  		start = ALIGN(entry->start, pg_size);
>>  		end   = ALIGN(entry->start + entry->length, pg_size);
>>  
>> +		if (entry->prot & IOMMU_RESV_MASK)
> 
> This seems to be the only place that this mask is used, and frankly I
> think it's less clear than simply "(IOMMU_RESV_NOMAP | IOMMU_RESV_MSI)"
> would be, at which point we may as well drop the mask and special value
> trickery altogether. Plus, per my previous comment, if it were to be "if
> (entry->type != <direct mapped type>)" instead, that's about as obvious
> as it can get.
OK I will add this new type entry in the reserved window struct.

thanks

Eric
> 
> Robin.
> 
>> +			continue;
>> +
>>  		for (addr = start; addr < end; addr += pg_size) {
>>  			phys_addr_t phys_addr;
>>  
>>
> 
> 
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> linux-arm-kernel@...ts.infradead.org
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>

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