linux-kernel - [RFC v1 1/2] powerpc/pseries/iommu: Share the per-cpu TCE page with the hypervisor.

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Message-Id: <1572902923-8096-2-git-send-email-linuxram@us.ibm.com>
Date:   Mon,  4 Nov 2019 13:28:42 -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 v1 1/2] powerpc/pseries/iommu: Share the per-cpu TCE page with the hypervisor.

The hypervisor needs to access the contents of the page holding the TCE
entries while setting up the TCE entries in the IOMMU's TCE table. For
SecureVMs, since this page is encrypted, the hypervisor cannot access
valid entries. Share the page with the hypervisor. This ensures that the
hypervisor sees the valid entries.

Signed-off-by: Ram Pai <linuxram@...ibm.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 8d9c2b1..07f0847 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -37,6 +37,7 @@
 #include <asm/mmzone.h>
 #include <asm/plpar_wrappers.h>
 #include <asm/svm.h>
+#include <asm/ultravisor.h>
 
 #include "pseries.h"
 
@@ -179,6 +180,19 @@ static int tce_build_pSeriesLP(struct iommu_table *tbl, long tcenum,
 
 static DEFINE_PER_CPU(__be64 *, tce_page);
 
+/*
+ * Allocate a tce page.  If secure VM, share the page with the hypervisor.
+ */
+static __be64 *alloc_tce_page(void)
+{
+	__be64 *tcep = (__be64 *)__get_free_page(GFP_ATOMIC);
+
+	if (tcep && is_secure_guest())
+		uv_share_page(PHYS_PFN(__pa(tcep)), 1);
+
+	return tcep;
+}
+
 static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
 				     long npages, unsigned long uaddr,
 				     enum dma_data_direction direction,
@@ -206,8 +220,7 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum,
 	 * from iommu_alloc{,_sg}()
 	 */
 	if (!tcep) {
-		tcep = (__be64 *)__get_free_page(GFP_ATOMIC);
-		/* If allocation fails, fall back to the loop implementation */
+		tcep = alloc_tce_page();
 		if (!tcep) {
 			local_irq_restore(flags);
 			return tce_build_pSeriesLP(tbl, tcenum, npages, uaddr,
@@ -391,6 +404,7 @@ static int tce_clearrange_multi_pSeriesLP(unsigned long start_pfn,
 	return rc;
 }
 
+
 static int tce_setrange_multi_pSeriesLP(unsigned long start_pfn,
 					unsigned long num_pfn, const void *arg)
 {
@@ -405,7 +419,7 @@ static int tce_setrange_multi_pSeriesLP(unsigned long start_pfn,
 	tcep = __this_cpu_read(tce_page);
 
 	if (!tcep) {
-		tcep = (__be64 *)__get_free_page(GFP_ATOMIC);
+		tcep = alloc_tce_page();
 		if (!tcep) {
 			local_irq_enable();
 			return -ENOMEM;
-- 
1.8.3.1