> From: Jane Malalane <jane.malal...@citrix.com> > Sent: Monday, March 7, 2022 11:06 PM > > Add XEN_SYSCTL_PHYSCAP_ARCH_ASSISTED_xapic and > XEN_SYSCTL_PHYSCAP_ARCH_ASSISTED_x2apic to report accelerated xapic > and x2apic, on x86 hardware. > No such features are currently implemented on AMD hardware. > > HW assisted xAPIC virtualization will be reported if HW, at the > minimum, supports virtualize_apic_accesses as this feature alone means > that an access to the APIC page will cause an APIC-access VM exit. An > APIC-access VM exit provides a VMM with information about the access > causing the VM exit, unlike a regular EPT fault, thus simplifying some > internal handling. > > HW assisted x2APIC virtualization will be reported if HW supports > virtualize_x2apic_mode and, at least, either apic_reg_virt or > virtual_intr_delivery. This is due to apic_reg_virt and > virtual_intr_delivery preventing a VM exit from occuring or at least > replacing a regular EPT fault VM-exit with an APIC-access VM-exit on > read and write APIC accesses, respectively. This also means that > sysctl follows the conditionals in vmx_vlapic_msr_changed(). > > For that purpose, also add an arch-specific "capabilities" parameter > to struct xen_sysctl_physinfo. > > Note that this interface is intended to be compatible with AMD so that > AVIC support can be introduced in a future patch. Unlike Intel that > has multiple controls for APIC Virtualization, AMD has one global > 'AVIC Enable' control bit, so fine-graining of APIC virtualization > control cannot be done on a common interface. > > Suggested-by: Andrew Cooper <andrew.coop...@citrix.com> > Signed-off-by: Jane Malalane <jane.malal...@citrix.com>
Can you add some explanation why this capability needs to be reported to toolstack? Thanks Kevin
