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Re: [libvirt] [PATCH RFC 1/3] qemu: Add check for whether nesting was enabled



On Tue, Nov 13, 2018 at 09:21 PM +0100, John Ferlan <jferlan redhat com> wrote:
> Support for nested kvm is handled via a kernel module configuration
> adjustment which if done after libvirtd is started and/or the last
> QEMU capabilities adjustment can result in the inability to start a
> guest and use nested kvm until the capabilities cache is invalidated.
>
> Thus, let's fetch and save the setting during initialization and then
> when the capabilities are checked for various host related adjustments
> that could affect whether the capabilities cache is updated add a check
> whether the nested value was set for either kvm_intel or kvm_amd to
> force a refetch of the capabilities.
>
> Signed-off-by: John Ferlan <jferlan redhat com>
> ---
>  src/qemu/qemu_capabilities.c | 43 ++++++++++++++++++++++++++++++++++++
>  src/qemu/qemu_capspriv.h     |  2 ++
>  tests/qemucapabilitiestest.c |  3 +++
>  3 files changed, 48 insertions(+)
>
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index 2ca5af3297..ebe0c0c7df 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -40,6 +40,7 @@
>  #include "virnodesuspend.h"
>  #include "virnuma.h"
>  #include "virhostcpu.h"
> +#include "virkmod.h"
>  #include "qemu_monitor.h"
>  #include "virstring.h"
>  #include "qemu_hostdev.h"
> @@ -551,6 +552,7 @@ struct _virQEMUCaps {
>      virObject parent;
>
>      bool usedQMP;
> +    bool isNested;
>
>      char *binary;
>      time_t ctime;
> @@ -1512,6 +1514,7 @@ virQEMUCapsPtr virQEMUCapsNewCopy(virQEMUCapsPtr qemuCaps)
>          return NULL;
>
>      ret->usedQMP = qemuCaps->usedQMP;
> +    ret->isNested = qemuCaps->isNested;
>
>      if (VIR_STRDUP(ret->binary, qemuCaps->binary) < 0)
>          goto error;
> @@ -3567,6 +3570,9 @@ virQEMUCapsLoadCache(virArch hostArch,
>      virQEMUCapsInitHostCPUModel(qemuCaps, hostArch, VIR_DOMAIN_VIRT_KVM);
>      virQEMUCapsInitHostCPUModel(qemuCaps, hostArch, VIR_DOMAIN_VIRT_QEMU);
>
> +    qemuCaps->isNested = virXPathBoolean("count(./isNested) > 0",
> +                                         ctxt) > 0;
> +
>      ret = 0;
>   cleanup:
>      VIR_FREE(str);
> @@ -3786,6 +3792,9 @@ virQEMUCapsFormatCache(virQEMUCapsPtr qemuCaps)
>      if (qemuCaps->sevCapabilities)
>          virQEMUCapsFormatSEVInfo(qemuCaps, &buf);
>
> +    if (qemuCaps->isNested)
> +        virBufferAddLit(&buf, "<isNested/>\n");
> +
>      virBufferAdjustIndent(&buf, -2);
>      virBufferAddLit(&buf, "</qemuCaps>\n");
>
> @@ -3826,6 +3835,28 @@ virQEMUCapsSaveFile(void *data,
>  }
>
>
> +static bool
> +virQEMUCapsIsNested(void)

Not sure if “isNested” is the best wording… Since we’re talking about
nested KVM support here.

> +{
> +    VIR_AUTOFREE(char *) kConfig = NULL;
> +
> +    if ((kConfig = virKModConfig()) &&
> +        (strstr(kConfig, "kvm_intel nested=1") ||
> +         strstr(kConfig, "kvm_amd nested=1")))

Please add a check for "kvm nested=1" here since this is used by s390x :)

> +        return true;
> +    return false;
> +}
> +
> +
> +void
> +virQEMUCapsClearIsNested(virQEMUCapsPtr qemuCaps)
> +{
> +    /* For qemucapabilitiestest to avoid printing the </isNested> on
> +     * hosts with nested set in the kernel */
> +    qemuCaps->isNested = false;
> +}
> +
> +
>  static bool
>  virQEMUCapsIsValid(void *data,
>                     void *privData)
> @@ -3834,6 +3865,7 @@ virQEMUCapsIsValid(void *data,
>      virQEMUCapsCachePrivPtr priv = privData;
>      bool kvmUsable;
>      struct stat sb;
> +    bool isNested;
>
>      if (!qemuCaps->binary)
>          return true;
> @@ -3866,6 +3898,15 @@ virQEMUCapsIsValid(void *data,
>          return false;
>      }
>
> +    /* Check if someone changed the nested={0|1} value for the kernel from
> +     * the previous time we checked. If so, then refresh the capabilities. */
> +    isNested = virQEMUCapsIsNested();
> +    if (isNested != qemuCaps->isNested) {
> +        VIR_WARN("changed kernel nested kvm value was %d", qemuCaps->isNested);
> +        qemuCaps->isNested = isNested;
> +        return false;
> +    }
> +
>      if (!virQEMUCapsGuestIsNative(priv->hostArch, qemuCaps->arch)) {
>          VIR_DEBUG("Guest arch (%s) is not native to host arch (%s), "
>                    "skipping KVM-related checks",
> @@ -4452,6 +4493,8 @@ virQEMUCapsInitQMP(virQEMUCapsPtr qemuCaps,
>      if (virQEMUCapsInitQMPMonitor(qemuCaps, cmd->mon) < 0)
>          goto cleanup;
>
> +    qemuCaps->isNested = virQEMUCapsIsNested();
> +
>      if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_KVM)) {
>          virQEMUCapsInitQMPCommandAbort(cmd);
>          if ((rc = virQEMUCapsInitQMPCommandRun(cmd, true)) != 0) {
> diff --git a/src/qemu/qemu_capspriv.h b/src/qemu/qemu_capspriv.h
> index 8d1a40fe74..b5d6aae2e5 100644
> --- a/src/qemu/qemu_capspriv.h
> +++ b/src/qemu/qemu_capspriv.h
> @@ -48,6 +48,8 @@ int
>  virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
>                            qemuMonitorPtr mon);
>
> +void virQEMUCapsClearIsNested(virQEMUCapsPtr qemuCaps);
> +
>  int
>  virQEMUCapsInitQMPMonitorTCG(virQEMUCapsPtr qemuCaps,
>                               qemuMonitorPtr mon);
> diff --git a/tests/qemucapabilitiestest.c b/tests/qemucapabilitiestest.c
> index 8fe5a55e1d..703fb6a125 100644
> --- a/tests/qemucapabilitiestest.c
> +++ b/tests/qemucapabilitiestest.c
> @@ -63,6 +63,9 @@ testQemuCaps(const void *opaque)
>                                    qemuMonitorTestGetMonitor(mon)) < 0)
>          goto cleanup;
>
> +    /* Don't apply what the host has... force clear for testing purposes */
> +    virQEMUCapsClearIsNested(capsActual);
> +
>      if (virQEMUCapsGet(capsActual, QEMU_CAPS_KVM)) {
>          qemuMonitorResetCommandID(qemuMonitorTestGetMonitor(mon));
>          if (virQEMUCapsInitQMPMonitorTCG(capsActual,
> --
> 2.17.2
>
> --
> libvir-list mailing list
> libvir-list redhat com
> https://www.redhat.com/mailman/listinfo/libvir-list
>
--
Kind regards / Beste Grüße
   Marc Hartmayer

IBM Deutschland Research & Development GmbH
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