Drivers: hv: vmbus: Initialize VMbus ring buffer for Isolation VM

VMbus ring buffer are shared with host and it's need to
be accessed via extra address space of Isolation VM with
AMD SNP support. This patch is to map the ring buffer
address in extra address space via vmap_pfn(). Hyperv set
memory host visibility hvcall smears data in the ring buffer
and so reset the ring buffer memory to zero after mapping.

Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Link: https://lore.kernel.org/r/20211025122116.264793-10-ltykernel@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

1 files changed, 42 insertions, 13 deletions

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 314015d9e912..931802ae985c 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -17,6 +17,8 @@
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
 #include <linux/prefetch.h>
+#include <linux/io.h>
+#include <asm/mshyperv.h>
 
 #include "hyperv_vmbus.h"
 
@@ -183,8 +185,10 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 		       struct page *pages, u32 page_cnt, u32 max_pkt_size)
 {
-	int i;
 	struct page **pages_wraparound;
+	unsigned long *pfns_wraparound;
+	u64 pfn;
+	int i;
 
 	BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
 
@@ -192,23 +196,48 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 	 * First page holds struct hv_ring_buffer, do wraparound mapping for
 	 * the rest.
 	 */
-	pages_wraparound = kcalloc(page_cnt * 2 - 1, sizeof(struct page *),
-				   GFP_KERNEL);
-	if (!pages_wraparound)
-		return -ENOMEM;
+	if (hv_isolation_type_snp()) {
+		pfn = page_to_pfn(pages) +
+			PFN_DOWN(ms_hyperv.shared_gpa_boundary);
+
+		pfns_wraparound = kcalloc(page_cnt * 2 - 1,
+			sizeof(unsigned long), GFP_KERNEL);
+		if (!pfns_wraparound)
+			return -ENOMEM;
+
+		pfns_wraparound[0] = pfn;
+		for (i = 0; i < 2 * (page_cnt - 1); i++)
+			pfns_wraparound[i + 1] = pfn + i % (page_cnt - 1) + 1;
 
-	pages_wraparound[0] = pages;
-	for (i = 0; i < 2 * (page_cnt - 1); i++)
-		pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
+		ring_info->ring_buffer = (struct hv_ring_buffer *)
+			vmap_pfn(pfns_wraparound, page_cnt * 2 - 1,
+				 PAGE_KERNEL);
+		kfree(pfns_wraparound);
 
-	ring_info->ring_buffer = (struct hv_ring_buffer *)
-		vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
+		if (!ring_info->ring_buffer)
+			return -ENOMEM;
+
+		/* Zero ring buffer after setting memory host visibility. */
+		memset(ring_info->ring_buffer, 0x00, PAGE_SIZE * page_cnt);
+	} else {
+		pages_wraparound = kcalloc(page_cnt * 2 - 1,
+					   sizeof(struct page *),
+					   GFP_KERNEL);
+
+		pages_wraparound[0] = pages;
+		for (i = 0; i < 2 * (page_cnt - 1); i++)
+			pages_wraparound[i + 1] =
+				&pages[i % (page_cnt - 1) + 1];
 
-	kfree(pages_wraparound);
+		ring_info->ring_buffer = (struct hv_ring_buffer *)
+			vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
+				PAGE_KERNEL);
 
+		kfree(pages_wraparound);
+		if (!ring_info->ring_buffer)
+			return -ENOMEM;
+	}
 
-	if (!ring_info->ring_buffer)
-		return -ENOMEM;
 
 	ring_info->ring_buffer->read_index =
 		ring_info->ring_buffer->write_index = 0;