[libvirt] [PATCH] tools/virt-host-validate: Fix IOMMU check on s390x

[Boris Fiuczynski]

On 2/27/19 10:48 AM, Thomas Huth wrote:
> On 27/02/2019 10.15, Bjoern Walk wrote:
>> With further testing...
>>
>> Thomas Huth <thuth at redhat.com> [2019-02-26, 12:02PM +0100]:
>>> When running virt-host-validate on an s390x host, the tool currently
>>> warns that it is "Unknown if this platform has IOMMU support".
>>> We can use the common check for entries in sys/kernel/iommu_groups here,
>>> too, but it only makes sense to check it if there are also PCI devices
>>> available. It's also common on s390x that there are no PCI devices
>>> assigned to the LPAR, and in that case there is no need for the
>>> PCI-related IOMMU, so without PCI devices we should simply skip this
>>> test.
>>>
>>> Signed-off-by: Thomas Huth <thuth at redhat.com>
>>> ---
>>>   tools/virt-host-validate-common.c | 11 +++++++++--
>>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tools/virt-host-validate-common.c b/tools/virt-host-validate-common.c
>>> index 73e3bdb..75c7cfc 100644
>>> --- a/tools/virt-host-validate-common.c
>>> +++ b/tools/virt-host-validate-common.c
>>> @@ -337,7 +337,7 @@ int virHostValidateIOMMU(const char *hvname,
>>>       virBitmapPtr flags;
>>>       struct stat sb;
>>>       const char *bootarg = NULL;
>>> -    bool isAMD = false, isIntel = false, isPPC = false;
>>> +    bool isAMD = false, isIntel = false, isPPC, isS390;
>>>       flags = virHostValidateGetCPUFlags();
>>>   
>>>       if (flags && virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_VMX))
>>> @@ -348,6 +348,7 @@ int virHostValidateIOMMU(const char *hvname,
>>>       virBitmapFree(flags);
>>>   
>>>       isPPC = ARCH_IS_PPC64(virArchFromHost());
>>> +    isS390 = ARCH_IS_S390(virArchFromHost());
>>>   
>>>       if (isIntel) {
>>>           virHostMsgCheck(hvname, "%s", _("for device assignment IOMMU support"));
>>> @@ -375,6 +376,12 @@ int virHostValidateIOMMU(const char *hvname,
>>>           }
>>>       } else if (isPPC) {
>>>           /* Empty Block */
>>> +    } else if (isS390) {
>>> +	/* On s390x, we skip the IOMMU check if there are no PCI devices
>>> +	 * (which is quite usual on s390x) */
>>> +        if (stat("/sys/bus/pci/devices", &sb) < 0 || !S_ISDIR(sb.st_mode) ||
>>> +            sb.st_nlink <= 2)
>>
>> ... this doesn't seem to work, no? The files in /sys/bus/pci/devices are
>> actually soft-links and are not counted by stat, am I wrong? At least on
>> my setup with a PCI device and populated sysfs it will still skip the
>> check.
> 
> Bummer. Stupid thinko. And I don't have a real PCI card for testing
> here, so I did not notice. So I guess I have to use opendir() +
> readdir() instead to find out if there are entries in this directory?
> 
>   Thomas
Thomas,
seems correct but you should use the libvirt wrappers.
I tried it out with this:

+    DIR *dir;
+    struct dirent *entry;
...
+        if (virDirOpenIfExists(&dir, "/sys/bus/pci/devices") > 0 &&
+            (virDirRead(dir, &entry, NULL)) <= 0)
              return 0;

...and it worked.
You want to add VIR_DIR_CLOSE(dir) somewhere as well.

> 
> 
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-- 
Mit freundlichen Grüßen/Kind regards
    Boris Fiuczynski

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