Received-SPF: pass (google.com: domain of linux-kernel+bounces-53140-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Date: Mon, 5 Feb 2024 13:45:07 -0400
From: Jason Gunthorpe <jgg@ziepe.ca>
To: James Gowans <jgowans@amazon.com>
Cc: linux-kernel@vger.kernel.org, Eric Biederman <ebiederm@xmission.com>,
	kexec@lists.infradead.org, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>, iommu@lists.linux.dev,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>,
	linux-fsdevel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>, kvm@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
	Alexander Graf <graf@amazon.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	"Jan H . Schoenherr" <jschoenh@amazon.de>,
	Usama Arif <usama.arif@bytedance.com>,
	Anthony Yznaga <anthony.yznaga@oracle.com>,
	Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>,
	madvenka@linux.microsoft.com, steven.sistare@oracle.com,
	yuleixzhang@tencent.com
Subject: Re: [RFC 11/18] dma-iommu: Always enable deferred attaches for
 liveupdate
Message-ID: <20240205174507.GD31743@ziepe.ca>
References: <20240205120203.60312-1-jgowans@amazon.com>
 <20240205120203.60312-12-jgowans@amazon.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240205120203.60312-12-jgowans@amazon.com>

On Mon, Feb 05, 2024 at 12:01:56PM +0000, James Gowans wrote:
> Seeing as translations are pre-enabled, all devices will be set for
> deferred attach. The deferred attached actually has to be done when
> doing DMA mapping for devices to work.

This shouldn't be part of your solution..

A DMA API using driver should never be attached to a device that is
being persisted across a kexec. If it does then the device should be
fully reset and re-attached to the normal DMA API iommu domain.

You should be striving to have an iommu_domain to represent the
special post-kexec translation regime.

Jason