[RFC PATCH V5 07/15] drivers: hv: Decrypt percpu hvcall input arg page in sev-snp enlightened guest

Tianyu Lan
2023-05-01T08:58:16Z

From: Tianyu Lan <tiala@microsoft.com>

Hypervisor needs to access iput arg page and guest should decrypt
the page.

Signed-off-by: Tianyu Lan <tiala@microsoft.com>
---
Change since RFC V4:
* Use pgcount to free intput arg page

Change since RFC V3:
* Use pgcount to decrypt memory.

Change since RFC V2:
* Set inputarg to be zero after kfree()
* Not free mem when fail to encrypt mem in the hv_common_cpu_die().
---
drivers/hv/hv_common.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 179bc5f5bf52..15d3054f3440 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -24,6 +24,7 @@
#include <linux/kmsg_dump.h>
#include <linux/slab.h>
#include <linux/dma-map-ops.h>
+#include <linux/set_memory.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>

@@ -359,6 +360,7 @@ int hv_common_cpu_init(unsigned int cpu)
u64 msr_vp_index;
gfp_t flags;
int pgcount = hv_root_partition ? 2 : 1;
+ int ret;

/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
@@ -368,6 +370,17 @@ int hv_common_cpu_init(unsigned int cpu)
if (!(*inputarg))
return -ENOMEM;

+ if (hv_isolation_type_en_snp()) {
+ ret = set_memory_decrypted((unsigned long)*inputarg, pgcount);
+ if (ret) {
+ kfree(*inputarg);
+ *inputarg = NULL;
+ return ret;
+ }
+
+ memset(*inputarg, 0x00, pgcount * PAGE_SIZE);
+ }
+
if (hv_root_partition) {
outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
@@ -387,6 +400,7 @@ int hv_common_cpu_die(unsigned int cpu)
{
unsigned long flags;
void **inputarg, **outputarg;
+ int pgcount = hv_root_partition ? 2 : 1;
void *mem;

local_irq_save(flags);
@@ -402,7 +416,12 @@ int hv_common_cpu_die(unsigned int cpu)

local_irq_restore(flags);

- kfree(mem);
+ if (hv_isolation_type_en_snp()) {
+ if (!set_memory_encrypted((unsigned long)mem, pgcount))
+ kfree(mem);
+ } else {
+ kfree(mem);
+ }

return 0;
}
--
2.25.1