[PATCH V4 08/13] hyperv/vmbus: Initialize VMbus ring buffer for Isolation VM

[Tianyu Lan <ltykernel@xxxxxxxxx>]

From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>

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.

Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
---
Change since v3:
        * Remove hv_ringbuffer_post_init(), merge map
        operation for Isolation VM into hv_ringbuffer_init()
        * Call hv_ringbuffer_init() after __vmbus_establish_gpadl().
---
 drivers/hv/Kconfig       |  1 +
 drivers/hv/channel.c     | 19 +++++++-------
 drivers/hv/ring_buffer.c | 56 ++++++++++++++++++++++++++++++----------
 3 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index d1123ceb38f3..dd12af20e467 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -8,6 +8,7 @@ config HYPERV
                || (ARM64 && !CPU_BIG_ENDIAN))
        select PARAVIRT
        select X86_HV_CALLBACK_VECTOR if X86
+       select VMAP_PFN
        help
          Select this option to run Linux as a Hyper-V client operating
          system.
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 82650beb3af0..81f8629e4491 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -679,15 +679,6 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
        if (!newchannel->max_pkt_size)
                newchannel->max_pkt_size = VMBUS_DEFAULT_MAX_PKT_SIZE;
 
-       err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages, 0);
-       if (err)
-               goto error_clean_ring;
-
-       err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
-                                recv_pages, newchannel->max_pkt_size);
-       if (err)
-               goto error_clean_ring;
-
        /* Establish the gpadl for the ring buffer */
        newchannel->ringbuffer_gpadlhandle = 0;
 
@@ -699,6 +690,16 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
        if (err)
                goto error_clean_ring;
 
+       err = hv_ringbuffer_init(&newchannel->outbound,
+                                page, send_pages, 0);
+       if (err)
+               goto error_free_gpadl;
+
+       err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
+                                recv_pages, newchannel->max_pkt_size);
+       if (err)
+               goto error_free_gpadl;
+
        /* Create and init the channel open message */
        open_info = kzalloc(sizeof(*open_info) +
                           sizeof(struct vmbus_channel_open_channel),
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 2aee356840a2..24d64d18eb65 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 +196,49 @@ 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) +
+                       HVPFN_DOWN(ms_hyperv.shared_gpa_boundary);
 
-       pages_wraparound[0] = pages;
-       for (i = 0; i < 2 * (page_cnt - 1); i++)
-               pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
+               pfns_wraparound = kcalloc(page_cnt * 2 - 1,
+                       sizeof(unsigned long), GFP_KERNEL);
+               if (!pfns_wraparound)
+                       return -ENOMEM;
 
-       ring_info->ring_buffer = (struct hv_ring_buffer *)
-               vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
+               pfns_wraparound[0] = pfn;
+               for (i = 0; i < 2 * (page_cnt - 1); i++)
+                       pfns_wraparound[i + 1] = pfn + i % (page_cnt - 1) + 1;
 
-       kfree(pages_wraparound);
+               ring_info->ring_buffer = (struct hv_ring_buffer *)
+                       vmap_pfn(pfns_wraparound, page_cnt * 2 - 1,
+                                PAGE_KERNEL);
+               kfree(pfns_wraparound);
 
+               if (!ring_info->ring_buffer)
+                       return -ENOMEM;
+
+               /* Zero ring buffer after setting memory host visibility. */
+               memset(ring_info->ring_buffer, 0x00,
+                       HV_HYP_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];
+
+               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;
-- 
2.25.1