[PATCH 5/6] tools: secure guest check for AMD in virt-host-validate

[Boris Fiuczynski <fiuczy@xxxxxxxxxxxxx>]

Add checking in virt-host-validate for secure guest support
on x86 for AMD Secure Encrypted Virtualization.

Signed-off-by: Boris Fiuczynski <fiuczy@xxxxxxxxxxxxx>
Reviewed-by: Paulo de Rezende Pinatti <ppinatti@xxxxxxxxxxxxx>
Reviewed-by: Bjoern Walk <bwalk@xxxxxxxxxxxxx>
---
 docs/kbase/launch_security_sev.rst |  7 ++++--
 tools/virt-host-validate-common.c  | 36 ++++++++++++++++++++++++++++--
 tools/virt-host-validate-common.h  |  1 +
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/docs/kbase/launch_security_sev.rst b/docs/kbase/launch_security_sev.rst
index fa602c7432..45166b3886 100644
--- a/docs/kbase/launch_security_sev.rst
+++ b/docs/kbase/launch_security_sev.rst
@@ -30,8 +30,11 @@ Enabling SEV on the host
 ========================
 
 Before VMs can make use of the SEV feature you need to make sure your
-AMD CPU does support SEV. You can check whether SEV is among the CPU
-flags with:
+AMD CPU does support SEV. You can run ``libvirt-host-validate``
+(libvirt >= 6.4.0) to check if your host supports secure guests or you
+can follow the manual checks below.
+
+You can manually check whether SEV is among the CPU flags with:
 
 ::
 
diff --git a/tools/virt-host-validate-common.c b/tools/virt-host-validate-common.c
index dd73bd0dea..67aa420d35 100644
--- a/tools/virt-host-validate-common.c
+++ b/tools/virt-host-validate-common.c
@@ -41,7 +41,8 @@ VIR_ENUM_IMPL(virHostValidateCPUFlag,
               "vmx",
               "svm",
               "sie",
-              "158");
+              "158",
+              "sev");
 
 static bool quiet;
 
@@ -447,15 +448,19 @@ int virHostValidateSecureGuests(const char *hvname,
                                 virHostValidateLevel level)
 {
     virBitmapPtr flags;
-    bool hasFac158 = false;
+    bool hasFac158 = false, hasAMDSev = false;
     virArch arch = virArchFromHost();
     g_autofree char *cmdline = NULL;
     static const char *kIBMValues[] = {"y", "Y", "1"};
+    static const char *kAMDValues[] = {"on"};
+    g_autofree char *mod_value = NULL;
 
     flags = virHostValidateGetCPUFlags();
 
     if (flags && virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_FACILITY_158))
         hasFac158 = true;
+    else if (flags && virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_SEV))
+        hasAMDSev = true;
 
     virBitmapFree(flags);
 
@@ -485,6 +490,33 @@ int virHostValidateSecureGuests(const char *hvname,
             virHostMsgFail(level, "Hardware or firmware does not provide "
                                   "support for IBM Secure Execution");
         }
+    } else if (hasAMDSev) {
+        if (virFileReadValueString(&mod_value, "/sys/module/kvm_amd/parameters/sev") < 0) {
+            virHostMsgFail(level, "AMD Secure Encrypted Virtualization not "
+                                  "supported by the currently used kernel");
+            return 0;
+        }
+        if (mod_value[0] != '1') {
+            virHostMsgFail(level,
+                           "AMD Secure Encrypted Virtualization appears to be "
+                           "disabled in kernel. Add mem_encrypt=on "
+                           "kvm_amd.sev=1 to kernel cmdline arguments");
+            return 0;
+        }
+        if (virFileReadValueString(&cmdline, "/proc/cmdline") < 0)
+            return -1;
+        if (virKernelCmdlineMatchParam(cmdline, "mem_encrypt", kAMDValues,
+                                       G_N_ELEMENTS(kAMDValues),
+                                       VIR_KERNEL_CMDLINE_FLAGS_SEARCH_LAST |
+                                       VIR_KERNEL_CMDLINE_FLAGS_CMP_EQ)) {
+            virHostMsgPass();
+            return 1;
+        } else {
+            virHostMsgFail(level,
+                           "AMD Secure Encrypted Virtualization appears to be "
+                           "disabled in kernel. Add mem_encrypt=on "
+                           "kvm_amd.sev=1 to kernel cmdline arguments");
+        }
     } else {
         virHostMsgFail(level,
                        "Unknown if this platform has Secure Guest support");
diff --git a/tools/virt-host-validate-common.h b/tools/virt-host-validate-common.h
index 44b5544a12..3df5ea0c7e 100644
--- a/tools/virt-host-validate-common.h
+++ b/tools/virt-host-validate-common.h
@@ -38,6 +38,7 @@ typedef enum {
     VIR_HOST_VALIDATE_CPU_FLAG_SVM,
     VIR_HOST_VALIDATE_CPU_FLAG_SIE,
     VIR_HOST_VALIDATE_CPU_FLAG_FACILITY_158,
+    VIR_HOST_VALIDATE_CPU_FLAG_SEV,
 
     VIR_HOST_VALIDATE_CPU_FLAG_LAST,
 } virHostValidateCPUFlag;
-- 
2.25.1