[Patch v4 08/13] Drivers: hv: vmbus: Remove second mapping of VMBus monitor pages

Michael Kelley
2022-12-02T03:34:02Z

With changes to how Hyper-V guest VMs flip memory between private
(encrypted) and shared (decrypted), creating a second kernel virtual
mapping for shared memory is no longer necessary. Everything needed
for the transition to shared is handled by set_memory_decrypted().

As such, remove the code to create and manage the second
mapping for VMBus monitor pages. Because set_memory_decrypted()
and set_memory_encrypted() are no-ops in normal VMs, it's
not even necessary to test for being in a Confidential VM
(a.k.a., "Isolation VM").

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
drivers/hv/connection.c | 113 ++++++++++++----------------------------------
drivers/hv/hyperv_vmbus.h | 2 -
2 files changed, 28 insertions(+), 87 deletions(-)

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 9dc27e5..f670cfd 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -104,8 +104,14 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
}

- msg->monitor_page1 = vmbus_connection.monitor_pages_pa[0];
- msg->monitor_page2 = vmbus_connection.monitor_pages_pa[1];
+ /*
+ * shared_gpa_boundary is zero in non-SNP VMs, so it's safe to always
+ * bitwise OR it
+ */
+ msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]) |
+ ms_hyperv.shared_gpa_boundary;
+ msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]) |
+ ms_hyperv.shared_gpa_boundary;

msg->target_vcpu = hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);

@@ -219,72 +225,27 @@ int vmbus_connect(void)
* Setup the monitor notification facility. The 1st page for
* parent->child and the 2nd page for child->parent
*/
- vmbus_connection.monitor_pages[0] = (void *)hv_alloc_hyperv_zeroed_page();
- vmbus_connection.monitor_pages[1] = (void *)hv_alloc_hyperv_zeroed_page();
+ vmbus_connection.monitor_pages[0] = (void *)hv_alloc_hyperv_page();
+ vmbus_connection.monitor_pages[1] = (void *)hv_alloc_hyperv_page();
if ((vmbus_connection.monitor_pages[0] == NULL) ||
(vmbus_connection.monitor_pages[1] == NULL)) {
ret = -ENOMEM;
goto cleanup;
}

- vmbus_connection.monitor_pages_original[0]
- = vmbus_connection.monitor_pages[0];
- vmbus_connection.monitor_pages_original[1]
- = vmbus_connection.monitor_pages[1];
- vmbus_connection.monitor_pages_pa[0]
- = virt_to_phys(vmbus_connection.monitor_pages[0]);
- vmbus_connection.monitor_pages_pa[1]
- = virt_to_phys(vmbus_connection.monitor_pages[1]);
-
- if (hv_is_isolation_supported()) {
- ret = set_memory_decrypted((unsigned long)
- vmbus_connection.monitor_pages[0],
- 1);
- ret |= set_memory_decrypted((unsigned long)
- vmbus_connection.monitor_pages[1],
- 1);
- if (ret)
- goto cleanup;
-
- /*
- * Isolation VM with AMD SNP needs to access monitor page via
- * address space above shared gpa boundary.
- */
- if (hv_isolation_type_snp()) {
- vmbus_connection.monitor_pages_pa[0] +=
- ms_hyperv.shared_gpa_boundary;
- vmbus_connection.monitor_pages_pa[1] +=
- ms_hyperv.shared_gpa_boundary;
-
- vmbus_connection.monitor_pages[0]
- = memremap(vmbus_connection.monitor_pages_pa[0],
- HV_HYP_PAGE_SIZE,
- MEMREMAP_WB);
- if (!vmbus_connection.monitor_pages[0]) {
- ret = -ENOMEM;
- goto cleanup;
- }
-
- vmbus_connection.monitor_pages[1]
- = memremap(vmbus_connection.monitor_pages_pa[1],
- HV_HYP_PAGE_SIZE,
- MEMREMAP_WB);
- if (!vmbus_connection.monitor_pages[1]) {
- ret = -ENOMEM;
- goto cleanup;
- }
- }
-
- /*
- * Set memory host visibility hvcall smears memory
- * and so zero monitor pages here.
- */
- memset(vmbus_connection.monitor_pages[0], 0x00,
- HV_HYP_PAGE_SIZE);
- memset(vmbus_connection.monitor_pages[1], 0x00,
- HV_HYP_PAGE_SIZE);
+ ret = set_memory_decrypted((unsigned long)
+ vmbus_connection.monitor_pages[0], 1);
+ ret |= set_memory_decrypted((unsigned long)
+ vmbus_connection.monitor_pages[1], 1);
+ if (ret)
+ goto cleanup;

- }
+ /*
+ * Set_memory_decrypted() will change the memory contents if
+ * decryption occurs, so zero monitor pages here.
+ */
+ memset(vmbus_connection.monitor_pages[0], 0x00, HV_HYP_PAGE_SIZE);
+ memset(vmbus_connection.monitor_pages[1], 0x00, HV_HYP_PAGE_SIZE);

msginfo = kzalloc(sizeof(*msginfo) +
sizeof(struct vmbus_channel_initiate_contact),
@@ -376,31 +337,13 @@ void vmbus_disconnect(void)
vmbus_connection.int_page = NULL;
}

- if (hv_is_isolation_supported()) {
- /*
- * memunmap() checks input address is ioremap address or not
- * inside. It doesn't unmap any thing in the non-SNP CVM and
- * so not check CVM type here.
- */
- memunmap(vmbus_connection.monitor_pages[0]);
- memunmap(vmbus_connection.monitor_pages[1]);
-
- set_memory_encrypted((unsigned long)
- vmbus_connection.monitor_pages_original[0],
- 1);
- set_memory_encrypted((unsigned long)
- vmbus_connection.monitor_pages_original[1],
- 1);
- }
+ set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[0], 1);
+ set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[1], 1);

- hv_free_hyperv_page((unsigned long)
- vmbus_connection.monitor_pages_original[0]);
- hv_free_hyperv_page((unsigned long)
- vmbus_connection.monitor_pages_original[1]);
- vmbus_connection.monitor_pages_original[0] =
- vmbus_connection.monitor_pages[0] = NULL;
- vmbus_connection.monitor_pages_original[1] =
- vmbus_connection.monitor_pages[1] = NULL;
+ hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[0]);
+ hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[1]);
+ vmbus_connection.monitor_pages[0] = NULL;
+ vmbus_connection.monitor_pages[1] = NULL;
}

/*
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index dc673ed..167ac51 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -241,8 +241,6 @@ struct vmbus_connection {
* is child->parent notification
*/
struct hv_monitor_page *monitor_pages[2];
- void *monitor_pages_original[2];
- phys_addr_t monitor_pages_pa[2];
struct list_head chn_msg_list;
spinlock_t channelmsg_lock;

--
1.8.3.1