linux-kernel - Re: [PATCH v5 00/11] IOMMU memory observability

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Message-ID: <CA+CK2bAiM_eC6k2EVL93uuOwB+hhV1WkDDK0YROo9-wAh=ju-w@mail.gmail.com>
Date: Thu, 4 Apr 2024 09:50:59 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Linu Cherian <lcherian@...vell.com>
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Subject: Re: [PATCH v5 00/11] IOMMU memory observability

> > Description
> > ----------------------------------------------------------------------
> > IOMMU subsystem may contain state that is in gigabytes. Majority of that
> > state is iommu page tables. Yet, there is currently, no way to observe
> > how much memory is actually used by the iommu subsystem.
> >
> > This patch series solves this problem by adding both observability to
> > all pages that are allocated by IOMMU, and also accountability, so
> > admins can limit the amount if via cgroups.
> >
> > The system-wide observability is using /proc/meminfo:
> > SecPageTables:    438176 kB
> >
> > Contains IOMMU and KVM memory.
>
> Can you please clarify what does KVM memory refers to here ?
> Does it mean the VFIO map / virtio-iommu invoked ones for a guest VM?

This means that nested page tables that are managed by KVM, and device
page tables that are managed by IOMMU are all accounted in
SecPageTables (secondary page tables). The decision to account them
both in one field of meminfo was made at LPC'23.

Pasha