Add upstream patch to use -cpu max.

0001-appliance-Use-cpu-max.patch

@@ -0,0 +1,80 @@
+From 282e2f74cf1209ecf6bb18655018b2000a5b36a1 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.
+
+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>
+---
+ 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 026dc6b26..eff1c8f7e 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 ();
+-- 
+2.29.0.rc2
+

libguestfs.spec

@@ -29,6 +29,7 @@
 %else
 # RHEL 9 only:
 # x86-64:  "/lib64/libc.so.6: CPU ISA level is lower than required"
+#          (RHBZ#1919389)
 %global test_arches NONE
 %endif
 
@@ -85,6 +86,9 @@ Source7:       libguestfs.keyring
 # Maintainer script which helps with handling patches.
 Source8:       copy-patches.sh
 
+# Upstream patch to use -cpu max.
+Patch1:        0001-appliance-Use-cpu-max.patch
+
 %if 0%{patches_touch_autotools}
 BuildRequires: autoconf, automake, libtool, gettext-devel
 %endif