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From 539a83390fb4b4b0dd7b029b7dd4ba2a345611cd Mon Sep 17 00:00:00 2001
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Message-Id: <539a83390fb4b4b0dd7b029b7dd4ba2a345611cd@dist-git>
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From: Jiri Denemark <jdenemar@redhat.com>
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Date: Tue, 4 Jun 2019 13:04:33 +0200
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Subject: [PATCH] qemu: Check TSC frequency before starting QEMU
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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When migrating a domain with invtsc CPU feature enabled, the TSC
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frequency of the destination host must match the frequency used when the
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domain was started on the source host or the destination host has to
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support TSC scaling.
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If the frequencies do not match and the destination host does not
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support TSC scaling, QEMU will fail to set the right TSC frequency when
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starting vCPUs on the destination and thus migration will fail. However,
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this is quite late since both host might have spent significant time
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transferring memory and perhaps even storage data.
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By adding the check to libvirt we can let migration fail before any data
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starts to be sent over. If for some reason libvirt is unable to detect
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the host's TSC frequency or scaling support, we'll just let QEMU try and
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the migration will either succeed or fail later.
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Luckily, we mandate TSC frequency to be explicitly set in the domain XML
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to even allow migration of domains with invtsc. We can just check
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whether the requested frequency is compatible with the current host
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before starting QEMU.
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https://bugzilla.redhat.com/show_bug.cgi?id=1641702
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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(cherry picked from commit 7da62c91f043209e3d40c2dc7655c5e35a4309bf)
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Conflicts:
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src/qemu/qemu_process.c
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- qemuProcessStartValidateXML function was removed upstream
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by commit v4.9.0-89-g91afd53cb8
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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Message-Id: <f5fcbf9d5afc4e156d1d2c888dc360d06bb29a1a.1559646067.git.jdenemar@redhat.com>
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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---
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src/qemu/qemu_process.c | 53 +++++++++++++++++++++++++++++++++++++++++
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1 file changed, 53 insertions(+)
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diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
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index 2795796166..7f70d79566 100644
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--- a/src/qemu/qemu_process.c
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+++ b/src/qemu/qemu_process.c
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@@ -5181,6 +5181,56 @@ qemuProcessStartValidateXML(virQEMUDriverPtr driver,
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}
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+static int
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+qemuProcessStartValidateTSC(virDomainObjPtr vm,
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+ virCapsPtr caps)
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+{
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+ size_t i;
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+ unsigned long long freq = 0;
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+ virHostCPUTscInfoPtr tsc;
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+
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+ for (i = 0; i < vm->def->clock.ntimers; i++) {
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+ virDomainTimerDefPtr timer = vm->def->clock.timers[i];
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+
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+ if (timer->name == VIR_DOMAIN_TIMER_NAME_TSC &&
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+ timer->frequency > 0) {
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+ freq = timer->frequency;
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+ break;
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+ }
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+ }
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+
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+ if (freq == 0)
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+ return 0;
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+
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+ VIR_DEBUG("Requested TSC frequency %llu Hz", freq);
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+
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+ if (!caps->host.cpu || !caps->host.cpu->tsc) {
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+ VIR_DEBUG("Host TSC frequency could not be probed");
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+ return 0;
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+ }
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+
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+ tsc = caps->host.cpu->tsc;
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+ VIR_DEBUG("Host TSC frequency %llu Hz, scaling %s",
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+ tsc->frequency, virTristateBoolTypeToString(tsc->scaling));
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+
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+ if (freq == tsc->frequency || tsc->scaling == VIR_TRISTATE_BOOL_YES)
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+ return 0;
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+
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+ if (tsc->scaling == VIR_TRISTATE_BOOL_ABSENT) {
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+ VIR_DEBUG("TSC frequencies do not match and scaling support is "
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+ "unknown, QEMU will try and possibly fail later");
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+ return 0;
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+ }
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+
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+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
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+ _("Requested TSC frequency %llu Hz does not match "
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+ "host (%llu Hz) and TSC scaling is not supported "
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+ "by the host CPU"),
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+ freq, tsc->frequency);
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+ return -1;
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+}
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+
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+
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/**
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* qemuProcessStartValidate:
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* @vm: domain object
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@@ -5241,6 +5291,9 @@ qemuProcessStartValidate(virQEMUDriverPtr driver,
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if (qemuProcessStartValidateDisks(vm, qemuCaps) < 0)
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return -1;
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+ if (qemuProcessStartValidateTSC(vm, caps) < 0)
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+ return -1;
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+
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VIR_DEBUG("Checking for any possible (non-fatal) issues");
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qemuProcessStartWarnShmem(vm);
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--
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2.21.0
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