linux-kernel - [PATCH hyperv-next v3 12/15] Drivers: hv: Allocate encrypted buffers when requested

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Message-ID: <20250604004341.7194-13-romank@linux.microsoft.com>
Date: Tue,  3 Jun 2025 17:43:38 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
To: alok.a.tiwari@...cle.com,
	arnd@...db.de,
	bp@...en8.de,
	corbet@....net,
	dave.hansen@...ux.intel.com,
	decui@...rosoft.com,
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	wei.liu@...nel.org,
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	linux-hyperv@...r.kernel.org,
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Cc: apais@...rosoft.com,
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Subject: [PATCH hyperv-next v3 12/15] Drivers: hv: Allocate encrypted buffers when requested

Confidential VMBus is built around using buffers not shared with
the host.

Support allocating encrypted buffers when requested.

Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
---
 drivers/hv/channel.c      | 43 +++++++++++++++++++++++----------------
 drivers/hv/hyperv_vmbus.h |  3 ++-
 drivers/hv/ring_buffer.c  |  5 +++--
 3 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index fb8cd8469328..3e2891c4b800 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -443,20 +443,23 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 		return ret;
 	}
 
-	/*
-	 * Set the "decrypted" flag to true for the set_memory_decrypted()
-	 * success case. In the failure case, the encryption state of the
-	 * memory is unknown. Leave "decrypted" as true to ensure the
-	 * memory will be leaked instead of going back on the free list.
-	 */
-	gpadl->decrypted = true;
-	ret = set_memory_decrypted((unsigned long)kbuffer,
-				   PFN_UP(size));
-	if (ret) {
-		dev_warn(&channel->device_obj->device,
-			 "Failed to set host visibility for new GPADL %d.\n",
-			 ret);
-		return ret;
+	gpadl->decrypted = !((channel->co_external_memory && type == HV_GPADL_BUFFER) ||
+		(channel->co_ring_buffer && type == HV_GPADL_RING));
+	if (gpadl->decrypted) {
+		/*
+		 * Set the "decrypted" flag to true for the set_memory_decrypted()
+		 * success case. In the failure case, the encryption state of the
+		 * memory is unknown. Leave "decrypted" as true to ensure the
+		 * memory will be leaked instead of going back on the free list.
+		 */
+		ret = set_memory_decrypted((unsigned long)kbuffer,
+					PFN_UP(size));
+		if (ret) {
+			dev_warn(&channel->device_obj->device,
+				"Failed to set host visibility for new GPADL %d.\n",
+				ret);
+			return ret;
+		}
 	}
 
 	init_completion(&msginfo->waitevent);
@@ -676,12 +679,13 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
 		goto error_clean_ring;
 
 	err = hv_ringbuffer_init(&newchannel->outbound,
-				 page, send_pages, 0);
+				 page, send_pages, 0, newchannel->co_ring_buffer);
 	if (err)
 		goto error_free_gpadl;
 
 	err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
-				 recv_pages, newchannel->max_pkt_size);
+				 recv_pages, newchannel->max_pkt_size,
+				 newchannel->co_ring_buffer);
 	if (err)
 		goto error_free_gpadl;
 
@@ -862,8 +866,11 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpad
 
 	kfree(info);
 
-	ret = set_memory_encrypted((unsigned long)gpadl->buffer,
-				   PFN_UP(gpadl->size));
+	if (gpadl->decrypted)
+		ret = set_memory_encrypted((unsigned long)gpadl->buffer,
+					PFN_UP(gpadl->size));
+	else
+		ret = 0;
 	if (ret)
 		pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
 
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index c1df611d1eb2..0f02e163b0a0 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -199,7 +199,8 @@ extern int hv_synic_cleanup(unsigned int cpu);
 void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
 
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
-		       struct page *pages, u32 pagecnt, u32 max_pkt_size);
+		       struct page *pages, u32 pagecnt, u32 max_pkt_size,
+			   bool confidential);
 
 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
 
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 3c9b02471760..05c2cd42fc75 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -183,7 +183,8 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
 
 /* Initialize the ring buffer. */
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
-		       struct page *pages, u32 page_cnt, u32 max_pkt_size)
+		       struct page *pages, u32 page_cnt, u32 max_pkt_size,
+			   bool confidential)
 {
 	struct page **pages_wraparound;
 	int i;
@@ -207,7 +208,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 
 	ring_info->ring_buffer = (struct hv_ring_buffer *)
 		vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
-			pgprot_decrypted(PAGE_KERNEL));
+			confidential ? PAGE_KERNEL : pgprot_decrypted(PAGE_KERNEL));
 
 	kfree(pages_wraparound);
 	if (!ring_info->ring_buffer)
-- 
2.43.0