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(a)redhat.com&gt; --- v2: - Use virDirOpen() + virDirRead() instead of stat() - this should hopefully work now as expected. tools/virt-host-validate-common.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/tools/virt-host-validate-common.c b/tools/virt-host-validate-common.c index 73e3bdb..e27b558 100644 --- a/tools/virt-host-validate-common.c +++ b/tools/virt-host-validate-common.c @@ -337,7 +337,12 @@ 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; + virArch arch = virArchFromHost(); + struct dirent *dent; + DIR *dir; + int rc; + flags = virHostValidateGetCPUFlags(); if (flags && virBitmapIsBitSet(flags, VIR_HOST_VALIDATE_CPU_FLAG_VMX)) @@ -347,8 +352,6 @@ int virHostValidateIOMMU(const char *hvname, virBitmapFree(flags); - isPPC = ARCH_IS_PPC64(virArchFromHost()); - if (isIntel) { virHostMsgCheck(hvname, "%s", _("for device assignment IOMMU support")); if (access("/sys/firmware/acpi/tables/DMAR", F_OK) == 0) { @@ -373,8 +376,17 @@ int virHostValidateIOMMU(const char *hvname, "hardware platform"); return -1; } - } else if (isPPC) { + } else if (ARCH_IS_PPC64(arch)) { /* Empty Block */ + } else if (ARCH_IS_S390(arch)) { + /* On s390x, we skip the IOMMU check if there are no PCI devices + * (which is quite usual on s390x) */ + if (!virDirOpen(&dir, "/sys/bus/pci/devices")) + return 0; + rc = virDirRead(dir, &dent, NULL); + VIR_DIR_CLOSE(dir);

On 07/03/2019 18.15, Michal Privoznik wrote: > On 3/1/19 12:10 PM, Thomas Huth wrote: >> 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(a)redhat.com&gt; >> --- >>   v2: >>   - Use virDirOpen() + virDirRead() instead of stat() - this should >> hopefully >>     work now as expected. >> >>   tools/virt-host-validate-common.c | 22 +++++++++++++++++----- >>   1 file changed, 17 insertions(+), 5 deletions(-) >> >> diff --git a/tools/virt-host-validate-common.c >> b/tools/virt-host-validate-common.c >> index 73e3bdb..e27b558 100644 >> --- a/tools/virt-host-validate-common.c >> +++ b/tools/virt-host-validate-common.c >> @@ -337,7 +337,12 @@ 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; >> +    virArch arch = virArchFromHost(); >> +    struct dirent *dent; >> +    DIR *dir; >> +    int rc; >> + >>       flags = virHostValidateGetCPUFlags(); >>         if (flags && virBitmapIsBitSet(flags, >> VIR_HOST_VALIDATE_CPU_FLAG_VMX)) >> @@ -347,8 +352,6 @@ int virHostValidateIOMMU(const char *hvname, >>         virBitmapFree(flags); >>   -    isPPC = ARCH_IS_PPC64(virArchFromHost()); >> - >>       if (isIntel) { >>           virHostMsgCheck(hvname, "%s", _("for device assignment IOMMU >> support")); >>           if (access("/sys/firmware/acpi/tables/DMAR", F_OK) == 0) { >> @@ -373,8 +376,17 @@ int virHostValidateIOMMU(const char *hvname, >>                              "hardware platform"); >>               return -1; >>           } >> -    } else if (isPPC) { >> +    } else if (ARCH_IS_PPC64(arch)) { >>           /* Empty Block */ >> +    } else if (ARCH_IS_S390(arch)) { >> +        /* On s390x, we skip the IOMMU check if there are no PCI devices >> +         * (which is quite usual on s390x) */ >> +        if (!virDirOpen(&dir, "/sys/bus/pci/devices")) >> +            return 0; >> +        rc = virDirRead(dir, &dent, NULL); >> +        VIR_DIR_CLOSE(dir); > > Is this diropen and dirread really necessary? Yes. > I mean, would something > like plain test of the path presence be okay, e.g. > virFileExists("/sys/bus/pci/devices"). No, that's unfortunately not enough. The "/sys/bus/pci/devices" directory is always present, even if there are no PCI devices available, it's just empty in that case. So as far as I can see, the dirread is necessary here.