From 52fc4aaf1613e49d018bf3c5b1899b131ee2f417 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Roger=20Pau=20Monn=C3=A9?= Date: Tue, 23 Jul 2019 17:00:07 +0200 Subject: [PATCH] x86/iommu: add comment regarding setting of need_sync MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Clarify why relaxed hardware domains don't need iommu page-table syncing. Signed-off-by: Roger Pau Monné Acked-by: Jan Beulich --- xen/drivers/passthrough/iommu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c index 79ec6719f5..f8c3bf53bd 100644 --- a/xen/drivers/passthrough/iommu.c +++ b/xen/drivers/passthrough/iommu.c @@ -185,6 +185,10 @@ void __hwdom_init iommu_hwdom_init(struct domain *d) register_keyhandler('o', &iommu_dump_p2m_table, "dump iommu p2m table", 0); hd->status = IOMMU_STATUS_initializing; + /* + * NB: relaxed hw domains don't need sync because all ram is already + * mapped in the iommu page tables. + */ hd->need_sync = iommu_hwdom_strict && !iommu_use_hap_pt(d); if ( need_iommu_pt_sync(d) ) { -- 2.39.5