qemu: report issues causing the kvm probe to fail

From: Christian Ehrhardt <[email protected]>

I ran into the issue of a failign KVM Probe of the qemu configure script three times this week always needing "set -x", inserting an exit, masking the cleanup trap and compiling the c file by hand until I knew what the reason is. I think we could make easier for developers and end users.
Therefore this patch keeps the qemu style configure output which is a list of "$Feature $Status", but extend the "no" result like "KVM Support no" with some more information.

There might be a lot of things going wrong with that probe and I don't want to handle all of them, but if it is one of the known checks e.g. for KVM_API_VERSION then we could grep/awk that out and report it. The patch reports in case of a known case in the style
"KVM support no - (Missing KVM capability KVM_CAP_DESTROY_MEMORY_REGION_WORKS)"

In case more than one #error is triggered it creates a comma separated list in those brackets and in case it is something else than an #error it just reports plain old "no".

I sent a similar patch matching kvm-userspace upstream version of this file to [email protected] to keep both in sync as much as possible.

---

[diffstat]

 configure |   23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

[diff]

index c534441..416a13b 100755
@@ -929,14 +929,18 @@ fi
 if test "$kvm" = "yes" ; then
     cat > $TMPC <<EOF
 #include <linux/kvm.h>
-#if !defined(KVM_API_VERSION) || \
-    KVM_API_VERSION < 12 || \
-    KVM_API_VERSION > 12 || \
-    !defined(KVM_CAP_USER_MEMORY) || \
-    !defined(KVM_CAP_SET_TSS_ADDR) || \
-    !defined(KVM_CAP_DESTROY_MEMORY_REGION_WORKS)
+#if !defined(KVM_API_VERSION) || KVM_API_VERSION < 12 || KVM_API_VERSION > 12
 #error Invalid KVM version
 #endif
+#if !defined(KVM_CAP_USER_MEMORY)
+#error Missing KVM capability KVM_CAP_USER_MEMORY
+#endif
+#if !defined(KVM_CAP_SET_TSS_ADDR)
+#error Missing KVM capability KVM_CAP_SET_TSS_ADDR
+#endif
+#if !defined(KVM_CAP_DESTROY_MEMORY_REGION_WORKS)
+#error Missing KVM capability KVM_CAP_DESTROY_MEMORY_REGION_WORKS
+#endif
 int main(void) { return 0; }
 EOF
   if test "$kerneldir" != "" ; then

@@ -948,7 +952,12 @@ EOF
       2>/dev/null ; then
     :
   else
-    kvm="no"
+    kvmprobeerr=`$cc $ARCH_CFLAGS -o $TMPE ${OS_CFLAGS} $kvm_cflags $TMPC 2>&1 | grep "error: #error " | awk --field-separator "error: #error " '{if (NR>1) printf(", "); printf("%s",$2);}'`
+    if test "$kvmprobeerr" != "" ; then
+      kvm="no - (${kvmprobeerr})"
+    else
+      kvm="no"
+    fi
   fi
 fi
 

We don't currently use awk in configure. Is awk available on all the crazy platforms QEMU builds on? Is it possible to do this without introducing a new configure dependency?

A graceful fail if awk isn't present (disabling KVM support) would be fine too.

Regards,

Anthony Liguori