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libguestfs/SOURCES/0020-appliance-Use-cpu-max....

87 lines
2.8 KiB

From fbb053fc71c0c072acb3fbf6e5fbbfc3b0667fd2 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Thu, 28 Jan 2021 12:20:49 +0000
Subject: [PATCH] appliance: Use -cpu max.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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QEMU has a newish feature (from about 2017 / qemu 2.9) called -cpu max
which is supposed to select the best CPU, ideal for libguestfs.
After this change, on x86-64:
KVM TCG
Direct -cpu max -cpu max
(non-libvirt)
Libvirt <cpu mode="host-passthrough"> <cpu mode="host-model">
<model fallback="allow"/> <model fallback="allow"/>
</cpu> </cpu>
Thanks: Daniel Berrangé
(cherry picked from commit 30f74f38bd6e42e783ba80895f4d6826abddd417)
---
lib/appliance-cpu.c | 16 ++++++++--------
lib/launch-libvirt.c | 9 +++++++++
2 files changed, 17 insertions(+), 8 deletions(-)
diff --git a/lib/appliance-cpu.c b/lib/appliance-cpu.c
index 5ef9f5c72..54ac6e2e3 100644
--- a/lib/appliance-cpu.c
+++ b/lib/appliance-cpu.c
@@ -38,6 +38,11 @@
*
* The literal string C<"host"> means use C<-cpu host>.
*
+ * =item C<"max">
+ *
+ * The literal string C<"max"> means use C<-cpu max> (the best
+ * possible). This requires awkward translation for libvirt.
+ *
* =item some string
*
* Some string such as C<"cortex-a57"> means use C<-cpu cortex-a57>.
@@ -80,14 +85,9 @@ guestfs_int_get_cpu_model (int kvm)
/* See discussion in https://bugzilla.redhat.com/show_bug.cgi?id=1605071 */
return NULL;
#else
- /* On most architectures, it is faster to pass the CPU host model to
- * the appliance, allowing maximum speed for things like checksums
- * and encryption. Only do this with KVM. It is broken in subtle
- * ways on TCG, and fairly pointless when you're emulating anyway.
+ /* On most architectures we can use "max" to get the best possible CPU.
+ * For recent qemu this should work even on TCG.
*/
- if (kvm)
- return "host";
- else
- return NULL;
+ return "max";
#endif
}
diff --git a/lib/launch-libvirt.c b/lib/launch-libvirt.c
index f6bb39d99..e3ff1ffe0 100644
--- a/lib/launch-libvirt.c
+++ b/lib/launch-libvirt.c
@@ -1169,6 +1169,15 @@ construct_libvirt_xml_cpu (guestfs_h *g,
attribute ("fallback", "allow");
} end_element ();
}
+ else if (STREQ (cpu_model, "max")) {
+ if (params->data->is_kvm)
+ attribute ("mode", "host-passthrough");
+ else
+ attribute ("mode", "host-model");
+ start_element ("model") {
+ attribute ("fallback", "allow");
+ } end_element ();
+ }
else
single_element ("model", cpu_model);
} end_element ();
--
2.31.1