81 lines
2.6 KiB
Diff
81 lines
2.6 KiB
Diff
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From 282e2f74cf1209ecf6bb18655018b2000a5b36a1 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Thu, 28 Jan 2021 12:20:49 +0000
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Subject: [PATCH] appliance: Use -cpu max.
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QEMU has a newish feature (from about 2017 / qemu 2.9) called -cpu max
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which is supposed to select the best CPU, ideal for libguestfs.
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After this change, on x86-64:
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KVM TCG
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Direct -cpu max -cpu max
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(non-libvirt)
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Libvirt <cpu mode="host-passthrough"> <cpu mode="host-model">
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<model fallback="allow"/> <model fallback="allow"/>
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</cpu> </cpu>
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---
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lib/appliance-cpu.c | 16 ++++++++--------
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lib/launch-libvirt.c | 9 +++++++++
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2 files changed, 17 insertions(+), 8 deletions(-)
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diff --git a/lib/appliance-cpu.c b/lib/appliance-cpu.c
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index 5ef9f5c72..54ac6e2e3 100644
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--- a/lib/appliance-cpu.c
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+++ b/lib/appliance-cpu.c
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@@ -38,6 +38,11 @@
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*
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* The literal string C<"host"> means use C<-cpu host>.
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*
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+ * =item C<"max">
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+ *
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+ * The literal string C<"max"> means use C<-cpu max> (the best
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+ * possible). This requires awkward translation for libvirt.
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+ *
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* =item some string
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*
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* Some string such as C<"cortex-a57"> means use C<-cpu cortex-a57>.
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@@ -80,14 +85,9 @@ guestfs_int_get_cpu_model (int kvm)
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/* See discussion in https://bugzilla.redhat.com/show_bug.cgi?id=1605071 */
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return NULL;
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#else
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- /* On most architectures, it is faster to pass the CPU host model to
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- * the appliance, allowing maximum speed for things like checksums
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- * and encryption. Only do this with KVM. It is broken in subtle
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- * ways on TCG, and fairly pointless when you're emulating anyway.
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+ /* On most architectures we can use "max" to get the best possible CPU.
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+ * For recent qemu this should work even on TCG.
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*/
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- if (kvm)
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- return "host";
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- else
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- return NULL;
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+ return "max";
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#endif
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}
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diff --git a/lib/launch-libvirt.c b/lib/launch-libvirt.c
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index 026dc6b26..eff1c8f7e 100644
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--- a/lib/launch-libvirt.c
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+++ b/lib/launch-libvirt.c
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@@ -1169,6 +1169,15 @@ construct_libvirt_xml_cpu (guestfs_h *g,
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attribute ("fallback", "allow");
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} end_element ();
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}
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+ else if (STREQ (cpu_model, "max")) {
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+ if (params->data->is_kvm)
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+ attribute ("mode", "host-passthrough");
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+ else
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+ attribute ("mode", "host-model");
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+ start_element ("model") {
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+ attribute ("fallback", "allow");
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+ } end_element ();
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+ }
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else
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single_element ("model", cpu_model);
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} end_element ();
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--
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2.29.0.rc2
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