[RFC PATCH V5 06/15] hv: vmbus: decrypt VMBus pages for sev-snp enlightened guest

Tianyu Lan
2023-05-01T08:58:01Z

From: Tianyu Lan <tiala@microsoft.com>

VMBus post msg, synic event and message pages are shared
with hypervisor and so decrypt these pages in the sev-snp guest.

Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
Change sicne RFC V4:
* Fix encrypt and free page order.

Change since RFC V3:
* Set encrypt page back in the hv_synic_free()

Change since RFC V2:
* Fix error in the error code path and encrypt
pages correctly when decryption failure happens.
---
drivers/hv/hv.c | 41 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index de6708dbe0df..e0943db51acd 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -20,6 +20,7 @@
#include <linux/interrupt.h>
#include <clocksource/hyperv_timer.h>
#include <asm/mshyperv.h>
+#include <linux/set_memory.h>
#include "hyperv_vmbus.h"

/* The one and only */
@@ -78,7 +79,7 @@ int hv_post_message(union hv_connection_id connection_id,

int hv_synic_alloc(void)
{
- int cpu;
+ int cpu, ret;
struct hv_per_cpu_context *hv_cpu;

/*
@@ -123,9 +124,33 @@ int hv_synic_alloc(void)
goto err;
}
}
+
+ if (hv_isolation_type_en_snp()) {
+ ret = set_memory_decrypted((unsigned long)
+ hv_cpu->synic_message_page, 1);
+ if (ret)
+ goto err;
+
+ ret = set_memory_decrypted((unsigned long)
+ hv_cpu->synic_event_page, 1);
+ if (ret)
+ goto err_decrypt_event_page;
+
+ memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
+ memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
+ }
}

return 0;
+
+err_decrypt_msg_page:
+ set_memory_encrypted((unsigned long)
+ hv_cpu->synic_event_page, 1);
+
+err_decrypt_event_page:
+ set_memory_encrypted((unsigned long)
+ hv_cpu->synic_message_page, 1);
+
err:
/*
* Any memory allocations that succeeded will be freed when
@@ -143,8 +168,18 @@ void hv_synic_free(void)
struct hv_per_cpu_context *hv_cpu
= per_cpu_ptr(hv_context.cpu_context, cpu);

- free_page((unsigned long)hv_cpu->synic_event_page);
- free_page((unsigned long)hv_cpu->synic_message_page);
+ if (hv_isolation_type_en_snp()) {
+ if (!set_memory_encrypted((unsigned long)
+ hv_cpu->synic_message_page, 1))
+ free_page((unsigned long)hv_cpu->synic_event_page);
+
+ if (!set_memory_encrypted((unsigned long)
+ hv_cpu->synic_event_page, 1))
+ free_page((unsigned long)hv_cpu->synic_message_page);
+ } else {
+ free_page((unsigned long)hv_cpu->synic_event_page);
+ free_page((unsigned long)hv_cpu->synic_message_page);
+ }
}

kfree(hv_context.hv_numa_map);
--
2.25.1