IOMMU Archive on lore.kernel.org
 help / color / Atom feed
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
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
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply index

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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=AADFC41AFE54684AB9EE6CBC0274A5D19D58F50F@SHSMSX104.ccr.corp.intel.com \
    --to=kevin.tian@intel.com \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=baolu.lu@linux.intel.com \
    --cc=dwmw2@infradead.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peterx@redhat.com \
    --cc=sanjay.k.kumar@intel.com \
    --cc=yi.y.sun@intel.com \
    --cc=yi.y.sun@linux.intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

IOMMU Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-iommu/0 linux-iommu/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-iommu linux-iommu/ https://lore.kernel.org/linux-iommu \
		iommu@lists.linux-foundation.org
	public-inbox-index linux-iommu

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.linux-foundation.lists.iommu


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git