From: Peter Xu <peterx@redhat.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: kevin.tian@intel.com, Yi Sun <yi.y.sun@linux.intel.com>,
ashok.raj@intel.com, kvm@vger.kernel.org,
sanjay.k.kumar@intel.com, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
Alex Williamson <alex.williamson@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
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 14:50:06 +0800 [thread overview]
Message-ID: <20190925065006.GN28074@xz-x1> (raw)
In-Reply-To: <20190923122454.9888-5-baolu.lu@linux.intel.com>
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?).
Regards,
--
Peter Xu
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2019-09-25 6:50 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 [this message]
2019-09-25 7:35 ` Tian, Kevin
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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