From 282e2f74cf1209ecf6bb18655018b2000a5b36a1 Mon Sep 17 00:00:00 2001 From: "Richard W.M. Jones" 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 --- 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