linux-kernel - [RFC 11/18] dma-iommu: Always enable deferred attaches for liveupdate

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Date: Mon, 5 Feb 2024 12:01:56 +0000
From: James Gowans <jgowans@...zon.com>
To: <linux-kernel@...r.kernel.org>
CC: Eric Biederman <ebiederm@...ssion.com>, <kexec@...ts.infradead.org>,
	"Joerg Roedel" <joro@...tes.org>, Will Deacon <will@...nel.org>,
	<iommu@...ts.linux.dev>, Alexander Viro <viro@...iv.linux.org.uk>, "Christian
 Brauner" <brauner@...nel.org>, <linux-fsdevel@...r.kernel.org>, Paolo Bonzini
	<pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>,
	<kvm@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	<linux-mm@...ck.org>, Alexander Graf <graf@...zon.com>, David Woodhouse
	<dwmw@...zon.co.uk>, "Jan H . Schoenherr" <jschoenh@...zon.de>, Usama Arif
	<usama.arif@...edance.com>, Anthony Yznaga <anthony.yznaga@...cle.com>,
	Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>,
	<madvenka@...ux.microsoft.com>, <steven.sistare@...cle.com>,
	<yuleixzhang@...cent.com>
Subject: [RFC 11/18] dma-iommu: Always enable deferred attaches for liveupdate

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.

There may be a better way to do this be, for example, consulting the
context entry table and only deferring attach if there is a persisted
context table entry for this device.
---
 drivers/iommu/dma-iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index e5d087bd6da1..76f916848f48 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1750,7 +1750,7 @@ void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 
 static int iommu_dma_init(void)
 {
-	if (is_kdump_kernel())
+	if (is_kdump_kernel() || liveupdate)
 		static_branch_enable(&iommu_deferred_attach_enabled);
 
 	return iova_cache_get();
-- 
2.40.1