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

[Bjoern Walk]

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.

> +            return 0;
>      } else {
>          virHostMsgFail(level,
>                         "Unknown if this platform has IOMMU support");
> @@ -391,7 +398,7 @@ int virHostValidateIOMMU(const char *hvname,
>  
>      virHostMsgCheck(hvname, "%s", _("if IOMMU is enabled by kernel"));
>      if (sb.st_nlink <= 2) {
> -        if (!isPPC)
> +        if (bootarg)
>              virHostMsgFail(level,
>                             "IOMMU appears to be disabled in kernel. "
>                             "Add %s to kernel cmdline arguments", bootarg);
> -- 
> 1.8.3.1
> 
> --
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> 

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