drivers: hv: Mark percpu hvcall input arg page unencrypted in SEV-SNP enlightened...

Hypervisor needs to access input arg, VMBus synic event and
message pages. Mark these pages unencrypted in the SEV-SNP
guest and free them only if they have been marked encrypted
successfully.

Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/20230818102919.1318039-5-ltykernel@gmail.com

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index de6708d..ec6e35a 100644 (file)
--- 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 = -ENOMEM;
        struct hv_per_cpu_context *hv_cpu;
 
        /*
@@ -123,26 +124,76 @@ 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) {
+                               pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
+                               hv_cpu->synic_message_page = NULL;
+
+                               /*
+                                * Free the event page here so that hv_synic_free()
+                                * won't later try to re-encrypt it.
+                                */
+                               free_page((unsigned long)hv_cpu->synic_event_page);
+                               hv_cpu->synic_event_page = NULL;
+                               goto err;
+                       }
+
+                       ret = set_memory_decrypted((unsigned long)
+                               hv_cpu->synic_event_page, 1);
+                       if (ret) {
+                               pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
+                               hv_cpu->synic_event_page = NULL;
+                               goto err;
+                       }
+
+                       memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
+                       memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
+               }
        }
 
        return 0;
+
 err:
        /*
         * Any memory allocations that succeeded will be freed when
         * the caller cleans up by calling hv_synic_free()
         */
-       return -ENOMEM;
+       return ret;
 }
 
 
 void hv_synic_free(void)
 {
-       int cpu;
+       int cpu, ret;
 
        for_each_present_cpu(cpu) {
                struct hv_per_cpu_context *hv_cpu
                        = per_cpu_ptr(hv_context.cpu_context, cpu);
 
+               /* It's better to leak the page if the encryption fails. */
+               if (hv_isolation_type_en_snp()) {
+                       if (hv_cpu->synic_message_page) {
+                               ret = set_memory_encrypted((unsigned long)
+                                       hv_cpu->synic_message_page, 1);
+                               if (ret) {
+                                       pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
+                                       hv_cpu->synic_message_page = NULL;
+                               }
+                       }
+
+                       if (hv_cpu->synic_event_page) {
+                               ret = set_memory_encrypted((unsigned long)
+                                       hv_cpu->synic_event_page, 1);
+                               if (ret) {
+                                       pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
+                                       hv_cpu->synic_event_page = NULL;
+                               }
+                       }
+               }
+
                free_page((unsigned long)hv_cpu->synic_event_page);
                free_page((unsigned long)hv_cpu->synic_message_page);
        }

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 4b4aa53..2d43ba2 100644 (file)
--- 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;
@@ -378,6 +380,17 @@ int hv_common_cpu_init(unsigned int cpu)
                        outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
                        *outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
                }
+
+               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);
+               }
        }
 
        msr_vp_index = hv_get_register(HV_REGISTER_VP_INDEX);