Re: [Regression] Re: [PATCH 18/18] iommu/vt-d: Remove IOVA handling code from the non-dma_ops path

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi Alex,

Thanks for the report.

On 6/18/20 4:06 AM, Alex Williamson wrote:
> On Sat, 16 May 2020 14:21:01 +0800
> Lu Baolu<baolu.lu@linux.intel.com>  wrote:
> 
>> From: Tom Murphy<murphyt7@tcd.ie>
>>
>> There's no need for the non-dma_ops path to keep track of IOVAs. The
>> whole point of the non-dma_ops path is that it allows the IOVAs to be
>> handled separately. The IOVA handling code removed in this patch is
>> pointless.
>>
>> Signed-off-by: Tom Murphy<murphyt7@tcd.ie>
>> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com>
>> ---
>>   drivers/iommu/intel-iommu.c | 95 +++++++++++++------------------------
>>   1 file changed, 32 insertions(+), 63 deletions(-)
> This commit results in a massive increase in memory use from the VT-d
> code.  I have a 16GB system where I reserve 7168 2MB hugespages for VM
> usage (14GB), leaving the host with 2GB.  I can no longer even boot the
> host in this configuration.  Bisecting to this commit, I find that
> reverting this change shows the following memory usage difference
> immediately after boot (no hugepages, nosmp, single user,
> intel_iommu=on iommu=pt):
> 
> @e70b081c6f37:
>               total        used        free      shared  buff/cache   available
> Mem:       16090860     2219372    13673044        1040      198444    13602664
> Swap:       2097148           0     2097148
> 
> reverting e70b081c6f37:
>                total        used        free      shared  buff/cache   available
> Mem:       16090852      101648    15789156        1040      200048    15719572
> Swap:       2097148           0     2097148
> 
> More than 2GB of additional memory used!  There's also a notable stall
> during bootup for this allocation:
> 
> [    9.703360] DMAR: No ATSR found
> [    9.709768] DMAR: dmar0: Using Queued invalidation
> [    9.719370] DMAR: dmar1: Using Queued invalidation
> 
> ### 4+ seconds! ###
> 
> [   14.076387] pci 0000:00:00.0: Adding to iommu group 0
> [   14.086515] pci 0000:00:01.0: Adding to iommu group 1
> [   14.096635] pci 0000:00:02.0: Adding to iommu group 2

Can you please try below changes?

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 887f184b900d..7eb29167e8f9 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2705,7 +2705,9 @@ static int __init si_domain_init(int hw)
                                     end >> agaw_to_width(si_domain->agaw)))
                                 continue;

-                       ret = iommu_domain_identity_map(si_domain, 
start, end);
+                       ret = iommu_domain_identity_map(si_domain,
+                                       mm_to_dma_pfn(start >> PAGE_SHIFT),
+                                       mm_to_dma_pfn(end >> PAGE_SHIFT));
                         if (ret)
                                 return ret;
                 }

Best regards,
baolu
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