linux-kernel - [RFC v2 2/2] powerpc/pseries/iommu: Use dma_iommu

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Message-Id: <1573254011-1604-3-git-send-email-linuxram@us.ibm.com>
Date:   Fri,  8 Nov 2019 15:00:11 -0800
From:   Ram Pai <linuxram@...ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     benh@...nel.crashing.org, david@...son.dropbear.id.au,
        mpe@...erman.id.au, paulus@...abs.org, mdroth@...ux.vnet.ibm.com,
        hch@....de, linuxram@...ibm.com, andmike@...ibm.com,
        sukadev@...ux.vnet.ibm.com, mst@...hat.com, ram.n.pai@...il.com,
        aik@...abs.ru, cai@....pw, tglx@...utronix.de,
        bauerman@...ux.ibm.com, linux-kernel@...r.kernel.org
Subject: [RFC v2 2/2] powerpc/pseries/iommu: Use dma_iommu_ops for Secure VMs aswell.

Commit edea902c1c1e disabled dma_iommu_ops path, for secure VMs. The
rationale for disabling the dma_iommu_ops path, was to enable use of the
dma_direct path, which had inbuilt support for bounce-buffering through
SWIOTLB.

However dma_iommu_ops is functionally much richer. Depending on the
capabilities of the platform, it can handle direct DMA; with or without
bounce buffering, and it can handle indirect DMA. Hence its better to
leverage the richer functionality supported by dma_iommu_ops.

Revert edea902c1c1e and renable dma_iommu_ops path for pseries Secure
VMs.

Signed-off-by: Ram Pai <linuxram@...ibm.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index a302aaa..3ffcb54 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -36,7 +36,6 @@
 #include <asm/udbg.h>
 #include <asm/mmzone.h>
 #include <asm/plpar_wrappers.h>
-#include <asm/svm.h>
 #include <asm/ultravisor.h>
 
 #include "pseries.h"
@@ -1336,15 +1335,7 @@ void iommu_init_early_pSeries(void)
 	of_reconfig_notifier_register(&iommu_reconfig_nb);
 	register_memory_notifier(&iommu_mem_nb);
 
-	/*
-	 * Secure guest memory is inacessible to devices so regular DMA isn't
-	 * possible.
-	 *
-	 * In that case keep devices' dma_map_ops as NULL so that the generic
-	 * DMA code path will use SWIOTLB to bounce buffers for DMA.
-	 */
-	if (!is_secure_guest())
-		set_pci_dma_ops(&dma_iommu_ops);
+	set_pci_dma_ops(&dma_iommu_ops);
 }
 
 static int __init disable_multitce(char *str)
-- 
1.8.3.1