[PATCH v6 3/8] x86/hyperv: Mark Hyper-V vp assist page unencrypted in SEV-SNP enlightened guest

Tianyu Lan
2023-08-16T16:00:11Z

hv vp assist page needs to be shared between SEV-SNP guest and Hyper-V.
So mark the page unencrypted in the SEV-SNP guest.

Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
arch/x86/hyperv/hv_init.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index f62ca3f6e9b2..8bd2603c5fc1 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -18,6 +18,7 @@
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
#include <asm/idtentry.h>
+#include <asm/set_memory.h>
#include <linux/kexec.h>
#include <linux/version.h>
#include <linux/vmalloc.h>
@@ -106,8 +107,21 @@ static int hv_cpu_init(unsigned int cpu)
* in hv_cpu_die(), otherwise a CPU may not be stopped in the
* case of CPU offlining and the VM will hang.
*/
- if (!*hvp)
+ if (!*hvp) {
*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
+
+ /*
+ * Hyper-V should never specify a VM that is a Confidential
+ * VM and also running in the root partition. Root partition
+ * is blocked to run in Confidential VM. So only decrypt assist
+ * page in non-root partition here.
+ */
+ if (*hvp && hv_isolation_type_en_snp()) {
+ WARN_ON_ONCE(set_memory_decrypted((unsigned long)(*hvp), 1));
+ memset(*hvp, 0, PAGE_SIZE);
+ }
+ }
+
if (*hvp)
msr.pfn = vmalloc_to_pfn(*hvp);

--
2.25.1