From: "Tian, Kevin" <kevin.tian@intel.com>
To: Peter Xu <peterx@redhat.com>, Lu Baolu <baolu.lu@linux.intel.com>
Cc: Yi Sun <yi.y.sun@linux.intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Alex Williamson <alex.williamson@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
"Sun, Yi Y" <yi.y.sun@intel.com>
Subject: RE: [RFC PATCH 4/4] iommu/vt-d: Identify domains using first level page table
Date: Wed, 25 Sep 2019 07:35:23 +0000 [thread overview]
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D19D58F50F@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <20190925065006.GN28074@xz-x1>
> From: Peter Xu [mailto:peterx@redhat.com]
> Sent: Wednesday, September 25, 2019 2:50 PM
>
> On Mon, Sep 23, 2019 at 08:24:54PM +0800, Lu Baolu wrote:
> > +/*
> > + * Check and return whether first level is used by default for
> > + * DMA translation.
> > + */
> > +static bool first_level_by_default(void)
> > +{
> > + struct dmar_drhd_unit *drhd;
> > + struct intel_iommu *iommu;
> > +
> > + rcu_read_lock();
> > + for_each_active_iommu(iommu, drhd)
> > + if (!sm_supported(iommu) ||
> > + !ecap_flts(iommu->ecap) ||
> > + !cap_caching_mode(iommu->cap))
> > + return false;
> > + rcu_read_unlock();
> > +
> > + return true;
> > +}
>
> "If no caching mode, then we will not use 1st level."
>
> Hmm, does the vIOMMU needs to support caching-mode if with the
> solution you proposed here? Caching mode is only necessary for
> shadowing AFAICT, and after all you're going to use full-nested,
> then... then I would think it's not needed. And if so, with this
> patch 1st level will be disabled. Sounds like a paradox...
>
> I'm thinking what would be the big picture for this to work now: For
> the vIOMMU, instead of exposing the caching-mode, I'm thinking maybe
> we should expose it with ecap.FLTS=1 while we can keep ecap.SLTS=0
> then it's natural that we can only use 1st level translation in the
> guest for all the domains (and I assume such an ecap value should
> never happen on real hardware, am I right?).
>
yes, that's also the picture in my mind. :-)
Thanks
Kevin
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next prev parent reply other threads:[~2019-09-25 7:35 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-23 12:24 [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 1/4] iommu/vt-d: Move domain_flush_cache helper into header Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 2/4] iommu/vt-d: Add first level page table interfaces Lu Baolu
2019-09-23 20:31 ` Raj, Ashok
2019-09-24 1:38 ` Lu Baolu
2019-09-25 4:30 ` Peter Xu
2019-09-25 4:38 ` Tian, Kevin
2019-09-25 5:24 ` Peter Xu
2019-09-25 6:52 ` Lu Baolu
2019-09-25 7:32 ` Tian, Kevin
2019-09-25 8:35 ` Peter Xu
2019-09-26 1:42 ` Lu Baolu
2019-09-25 5:21 ` Peter Xu
2019-09-26 2:35 ` Lu Baolu
2019-09-26 3:49 ` Peter Xu
2019-09-27 2:27 ` Lu Baolu
2019-09-27 5:34 ` Peter Xu
2019-09-28 8:23 ` Lu Baolu
2019-09-29 5:25 ` Peter Xu
2019-10-08 2:20 ` Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 3/4] iommu/vt-d: Map/unmap domain with mmmap/mmunmap Lu Baolu
2019-09-25 5:00 ` Tian, Kevin
2019-09-25 7:06 ` Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 4/4] iommu/vt-d: Identify domains using first level page table Lu Baolu
2019-09-25 6:50 ` Peter Xu
2019-09-25 7:35 ` Tian, Kevin [this message]
2019-09-23 19:27 ` [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest Jacob Pan
2019-09-23 20:25 ` Raj, Ashok
2019-09-24 4:40 ` Lu Baolu
2019-09-24 7:00 ` Tian, Kevin
2019-09-25 2:48 ` Lu Baolu
2019-09-25 6:56 ` Peter Xu
2019-09-25 7:21 ` Tian, Kevin
2019-09-25 7:45 ` Peter Xu
2019-09-25 8:02 ` Tian, Kevin
2019-09-25 8:52 ` Peter Xu
2019-09-26 1:37 ` Lu Baolu
2019-09-24 4:27 ` Lu Baolu
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