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* min_align_mask Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver
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@ 2021-08-24  8:49         ` hch
  0 siblings, 0 replies; only message in thread
From: hch @ 2021-08-24  8:49 UTC (permalink / raw)
  To: Michael Kelley
  Cc: hch@lst.de, Tianyu Lan, KY Srinivasan, Haiyang Zhang,
	Stephen Hemminger, wei.liu@kernel.org, Dexuan Cui,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com,
	luto@kernel.org, peterz@infradead.org, konrad.wilk@oracle.com,
	boris.ostrovsky@oracle.com, jgross@suse.com,
	sstabellini@kernel.org, joro@8bytes.org, will@kernel.org,
	davem@davemloft.net, kuba@kernel.org, jejb@linux.ibm.com,
	martin.petersen@oracle.com, arnd@arndb.de,
	m.szyprowski@samsung.com, robin.murphy@arm.com,
	thomas.lendacky@amd.com, brijesh.singh@amd.com, ardb@kernel.org,
	Tianyu Lan, pgonda@google.com, martin.b.radev@gmail.com,
	akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
	rppt@kernel.org, sfr@canb.auug.org.au, saravanand@fb.com,
	krish.sadhukhan@oracle.com, aneesh.kumar@linux.ibm.com,
	xen-devel@lists.xenproject.org, rientjes@google.com,
	hannes@cmpxchg.org, tj@kernel.org,
	iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org,
	linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-scsi@vger.kernel.org, netdev@vger.kernel.org, vkuznets,
	parri.andrea@gmail.com, dave.hansen@intel.com, linux-rdma,
	mpi3mr-linuxdrv.pdl

On Fri, Aug 20, 2021 at 03:40:08PM +0000, Michael Kelley wrote:
> I see that the swiotlb code gets and uses the min_align_mask field.  But
> the NVME driver is the only driver that ever sets it, so the value is zero
> in all other cases.  Does swiotlb just use PAGE_SIZE in that that case?  I
> couldn't tell from a quick glance at the swiotlb code.

The encoding isn't all that common.  I only know it for the RDMA memory
registration format, and RDMA in general does not interact very well
with swiotlb (although the in-kernel drivers should work fine, it is
userspace RDMA that is the problem).  It seems recently a new driver
using the format (mpi3mr) also showed up.  All these should probably set
the min_align_mask.

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2021-08-24  8:49         ` min_align_mask Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver hch

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