> > 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.
Yes, This series will expose all the HW capabilities to KVM guest if the Intel PT is supported in the guest. > > Does it mean the plan is to drop intel-pt migration support entirely? I don't want to drop intel-pt live migration feature. As discussed with you before, the Intel PT feature includes some sub-features and may be different on each HW platform. Expose all the capabilities to the guest can't make live migration safe. Do you have any new proposals? Thanks, Luwei Kang > > > > > 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
