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[libvirt] [PATCH] host-validate: Improve CPU flags processing



Instead of relying on substring search, tokenize the input
and process each CPU flag separately. This ensures CPU flag
detection will continue to work correctly even if we start
looking for CPU flags whose name might appear as part of
other CPU flags' names.

The result of processing is stored in a virBitmap, which
means we don't have to parse /proc/cpuinfo in its entirety
for each single CPU flag we want to check.

Moreover, use of the newly-introduced virHostValidateCPUFlag
enumeration ensures we don't go looking for random CPU flags
which might actually be simple typos.
---
The concern was raised by John in

  https://www.redhat.com/archives/libvir-list/2016-March/msg01301.html

when discussing a new check on the "sie" CPU flag.

 tools/virt-host-validate-common.c | 50 +++++++++++++++++++++++++++++----------
 tools/virt-host-validate-common.h | 13 +++++++++-
 tools/virt-host-validate-qemu.c   | 12 ++++++++--
 3 files changed, 60 insertions(+), 15 deletions(-)

diff --git a/tools/virt-host-validate-common.c b/tools/virt-host-validate-common.c
index 8ebf73e..57fa332 100644
--- a/tools/virt-host-validate-common.c
+++ b/tools/virt-host-validate-common.c
@@ -31,7 +31,6 @@
 #endif /* HAVE_MNTENT_H */
 #include <sys/stat.h>
 
-#include "virutil.h"
 #include "viralloc.h"
 #include "virfile.h"
 #include "virt-host-validate-common.h"
@@ -39,6 +38,10 @@
 
 #define VIR_FROM_THIS VIR_FROM_NONE
 
+VIR_ENUM_IMPL(virHostValidateCPUFlag, VIR_HOST_VALIDATE_CPU_FLAG_LAST,
+              "vmx",
+              "svm");
+
 static bool quiet;
 
 void virHostMsgSetQuiet(bool quietFlag)
@@ -188,29 +191,47 @@ int virHostValidateNamespace(const char *hvname,
 }
 
 
-bool virHostValidateHasCPUFlag(const char *name)
+virBitmapPtr virHostValidateGetCPUFlags(void)
 {
-    FILE *fp = fopen("/proc/cpuinfo", "r");
-    bool ret = false;
+    FILE *fp;
+    virBitmapPtr flags;
 
-    if (!fp)
-        return false;
+    if (!(fp = fopen("/proc/cpuinfo", "r")))
+        return NULL;
+
+    if (!(flags = virBitmapNewQuiet(VIR_HOST_VALIDATE_CPU_FLAG_LAST)))
+        return NULL;
 
     do {
         char line[1024];
+        char *saveptr;
+        char *token;
 
         if (!fgets(line, sizeof(line), fp))
             break;
 
-        if (strstr(line, name)) {
-            ret = true;
-            break;
+        if (!(token = strtok_r(line, " \t\n", &saveptr)))
+            continue;
+
+        /* The line we're interested in is marked either as "flags" or
+         * as "Features" depending on the architecture, so check both
+         * prefixes. It's very unlikely that there will be no whitespace
+         * between the line name and the colon, but handle that as well */
+        if (strcmp(token, "flags") && strcmp(token, "flags:") &&
+            strcmp(token, "Features") && strcmp(token, "Features:"))
+            continue;
+
+        while ((token = strtok_r(NULL, " \t\n", &saveptr))) {
+            int value;
+
+            if ((value = virHostValidateCPUFlagTypeFromString(token)) >= 0)
+                ignore_value(virBitmapSetBit(flags, value));
         }
     } while (1);
 
     VIR_FORCE_FCLOSE(fp);
 
-    return ret;
+    return flags;
 }
 
 
@@ -359,15 +380,20 @@ int virHostValidateCGroupController(const char *hvname,
 int virHostValidateIOMMU(const char *hvname,
                          virHostValidateLevel level)
 {
+    virBitmapPtr flags;
     struct stat sb;
     const char *bootarg = NULL;
     bool isAMD = false, isIntel = false;
 
-    if (virHostValidateHasCPUFlag("vmx"))
+    flags = virHostValidateGetCPUFlags();
+
+    if (flags && virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_VMX))
         isIntel = true;
-    else if (virHostValidateHasCPUFlag("svm"))
+    else if (flags && virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_SVM))
         isAMD = true;
 
+    virBitmapFree(flags);
+
     virHostMsgCheck(hvname, "%s", _("for device assignment IOMMU support"));
 
     if (isIntel) {
diff --git a/tools/virt-host-validate-common.h b/tools/virt-host-validate-common.h
index d4c4759..26e006b 100644
--- a/tools/virt-host-validate-common.h
+++ b/tools/virt-host-validate-common.h
@@ -23,6 +23,8 @@
 # define __VIRT_HOST_VALIDATE_COMMON_H__
 
 # include "internal.h"
+# include "virutil.h"
+# include "virbitmap.h"
 
 typedef enum {
     VIR_HOST_VALIDATE_FAIL,
@@ -32,6 +34,15 @@ typedef enum {
     VIR_HOST_VALIDATE_LAST,
 } virHostValidateLevel;
 
+typedef enum {
+    VIR_HOST_VALIDATE_CPU_FLAG_VMX = 0,
+    VIR_HOST_VALIDATE_CPU_FLAG_SVM,
+
+    VIR_HOST_VALIDATE_CPU_FLAG_LAST,
+} virHostValidateCPUFlag;
+
+VIR_ENUM_DECL(virHostValidateCPUFlag);
+
 extern void virHostMsgSetQuiet(bool quietFlag);
 
 extern void virHostMsgCheck(const char *prefix,
@@ -53,7 +64,7 @@ extern int virHostValidateDeviceAccessible(const char *hvname,
                                            virHostValidateLevel level,
                                            const char *hint);
 
-extern bool virHostValidateHasCPUFlag(const char *name);
+extern virBitmapPtr virHostValidateGetCPUFlags(void);
 
 extern int virHostValidateLinuxKernel(const char *hvname,
                                       int version,
diff --git a/tools/virt-host-validate-qemu.c b/tools/virt-host-validate-qemu.c
index a9f6c1e..b96b020 100644
--- a/tools/virt-host-validate-qemu.c
+++ b/tools/virt-host-validate-qemu.c
@@ -24,14 +24,20 @@
 
 #include "virt-host-validate-qemu.h"
 #include "virt-host-validate-common.h"
+#include "virbitmap.h"
 
 int virHostValidateQEMU(void)
 {
+    virBitmapPtr flags;
     int ret = 0;
 
     virHostMsgCheck("QEMU", "%s", ("for hardware virtualization"));
-    if (virHostValidateHasCPUFlag("svm") ||
-        virHostValidateHasCPUFlag("vmx")) {
+
+    flags = virHostValidateGetCPUFlags();
+
+    if (flags &&
+        (virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_SVM) ||
+         virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_VMX))) {
         virHostMsgPass();
         if (virHostValidateDeviceExists("QEMU", "/dev/kvm",
                                         VIR_HOST_VALIDATE_FAIL,
@@ -48,6 +54,8 @@ int virHostValidateQEMU(void)
                        _("Only emulated CPUs are available, performance will be significantly limited"));
     }
 
+    virBitmapFree(flags);
+
     if (virHostValidateDeviceExists("QEMU", "/dev/vhost-net",
                                     VIR_HOST_VALIDATE_WARN,
                                     _("Load the 'vhost_net' module to improve performance "
-- 
2.5.5


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