Re: [PATCH v2] iommu/vt-d: Make DMAR_UNITS_SUPPORTED a config setting

From: Steve Wahl <steve.wahl@hpe.com>
To: Baolu Lu <baolu.lu@linux.intel.com>
Cc: Steve Wahl <steve.wahl@hpe.com>, Joerg Roedel <jroedel@suse.de>,
	David Woodhouse <dwmw2@infradead.org>,
	Will Deacon <will@kernel.org>,
	iommu@lists.linux-foundation.org,
	Mike Travis <mike.travis@hpe.com>,
	Dimitri Sivanich <sivanich@hpe.com>,
	Russ Anderson <russ.anderson@hpe.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] iommu/vt-d: Make DMAR_UNITS_SUPPORTED a config setting
Date: Wed, 18 May 2022 14:58:23 -0500	[thread overview]
Message-ID: <YoVP3w5cJWriLBlu@swahl-home.5wahls.com> (raw)
In-Reply-To: <2c65b8cf-3813-3ddf-3f5b-c374cc842678@linux.intel.com>

On Fri, May 13, 2022 at 10:09:46AM +0800, Baolu Lu wrote:
> On 2022/5/13 07:12, Steve Wahl wrote:
> > On Thu, May 12, 2022 at 10:13:09AM -0500, Steve Wahl wrote:
> > > To support up to 64 sockets with 10 DMAR units each (640), make the
> > > value of DMAR_UNITS_SUPPORTED adjustable by a config variable,
> > > CONFIG_DMAR_UNITS_SUPPORTED, and make it's default 1024 when MAXSMP is
> > > set.
> > > 
> > > If the available hardware exceeds DMAR_UNITS_SUPPORTED (previously set
> > > to MAX_IO_APICS, or 128), it causes these messages: "DMAR: Failed to
> > > allocate seq_id", "DMAR: Parse DMAR table failure.", and "x2apic: IRQ
> > > remapping doesn't support X2APIC mode x2apic disabled"; and the system
> > > fails to boot properly.
> > > 
> > > Signed-off-by: Steve Wahl <steve.wahl@hpe.com>
> > 
> > I've received a report from the kernel test robot <lkp@intel.com>,
> > that this patch causes an error (shown below) when
> > CONFIG_IOMMU_SUPPORT is not set.
> > 
> > In my opinion, this is because include/linux/dmar.h and
> > include/linux/intel-iommu are being #included when they are not really
> > being used.
> > 
> > I've tried placing the contents of intel-iommu.h within an #ifdef
> > CONFIG_INTEL_IOMMU, and that fixes the problem.
> > 
> > Two questions:
> > 
> > A) Is this the desired approach to to the fix?
> 
> Most part of include/linux/intel-iommu.h is private to Intel IOMMU
> driver. They should be put in a header like drivers/iommu/intel
> /iommu.h. Eventually, we should remove include/linux/intel-iommu.h
> and device drivers interact with iommu subsystem through the IOMMU
> kAPIs.
> 
> Best regards,
> baolu

Baolu's recent patch to move intel-iommu.h private still allows my
[PATCH v2] to apply with no changes, and gets rid of the compile
errors when CONFIG_IOMMU_SUPPORT is not set, so the kernel test robot
should be happy now.

Is there another step I should do to bring this patch back into focus?

Thanks.

--> Steve

-- 
Steve Wahl, Hewlett Packard Enterprise