On Mon, Sep 21, 2020 at 07:49:22AM +0000, Kang, Luwei wrote: > Hi Eduardo, > This patch set will remove some limitations of Intel PT CPUID information. > 1. The "IP payloads" feature will disable the Intel PT in guests and it > will be coming soon. > 2. To make the live migration safe, we set the Intel PT CPUID as a > constant value(Icelake server CPUID). It will mask off the new feature of > Intel PT.
Isn't this series doing the opposite of 2? It replaces all constant CPUID values with kvm_arch_get_supported_cpuid(), making the feature unavailable in migration-safe mode. Does it mean the plan is to drop intel-pt migration support entirely? > > About this issue https://bugzilla.redhat.com/show_bug.cgi?id=1853972, > Intel PT is disabled in the guest by default, we should use "-cpu > Icelake-Server,+intel-pt" to enable the Intel PT. That's correct. The point of the BZ is that libvirt mode=host-model was expected to include intel-pt automatically when available. With this series, the request in the BZ stops making sense (because intel-pt won't be migration-safe anymore), but I'm not sure yet that's really the plan. > > Thanks, > Luwei Kang > > > -----Original Message----- > > From: Eduardo Habkost <ehabk...@redhat.com> > > Sent: Saturday, September 19, 2020 6:03 AM > > To: Kang, Luwei <luwei.k...@intel.com> > > Cc: pbonz...@redhat.com; r...@twiddle.net; qemu-devel@nongnu.org; Strong, > > Beeman <beeman.str...@intel.com>; Jiri Denemark > > <jdene...@redhat.com>; Robert Hoo <robert...@linux.intel.com> > > Subject: Re: [PATCH v1 0/3] Remove the limitation of Intel PT CPUID info > > > > Hi Luwei Kang, > > > > I was looking for info on intel-pt and just saw this series, and it was > > never > > reviewed or merged (sorry for missing it!). Is this still the approach we > > want to > > follow for intel-pt? > > > > I'm CCing Jiri Denemark because this might be relevant for a libvirt issue > > related > > to intel-pt we were investigating[1]. > > > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=1853972 > > > > > > On Mon, Mar 30, 2020 at 09:56:09AM +0000, Kang, Luwei wrote: > > > > -----Original Message----- > > > > From: Kang, Luwei <luwei.k...@intel.com> > > > > Sent: Tuesday, February 25, 2020 5:38 AM > > > > To: pbonz...@redhat.com; r...@twiddle.net; ehabk...@redhat.com > > > > Cc: qemu-devel@nongnu.org; Strong, Beeman > > <beeman.str...@intel.com>; > > > > Kang, Luwei <luwei.k...@intel.com> > > > > Subject: [PATCH v1 0/3] Remove the limitation of Intel PT CPUID info > > > > > > > > The Intel PT feature includes some > > > > sub-features(CPUID.(EAX=14H,ECX=0H)) > > > > and these sub-features are different on different HW platforms. To > > > > make the live migration safety(get the same CPUID info with same cpu > > > > model on different HW platform), the current Intel PT CPUID > > > > information is set to a constant value(from ICELAKE Server). > > > > > > > > It will block the new feature in the later HW platform. what's more, > > > > the support of "IP payloads" will disable the Intel PT in KVM > > > > guest(patch 1) but it will come soon. > > > > > > > > This patchset remove this limitation and expose all the capabilities > > > > to KVM guest. As it will break the live migration safe, Intel PT > > > > will be masked as unmigratable. > > > > > > Ping. > > > > > > Thanks, > > > Luwei Kang > > > > > > > > > > > Luwei Kang (3): > > > > i386: Remove the limitation of IP payloads for Intel PT > > > > i386: Remove the CPUID limitation of Intel PT > > > > i386: Mark the 'INTEL_PT' CPUID bit as unmigratable > > > > > > > > target/i386/cpu.c | 69 > > > > ++++--------------------------------------------------- > > > > 1 file changed, 5 insertions(+), 64 deletions(-) > > > > > > > > -- > > > > 1.8.3.1 > > > > > > > -- > > Eduardo > -- Eduardo
