On 29/06/2022 15:26, Jan Beulich wrote:
> On 29.06.2022 15:55, Jane Malalane wrote:
>> Add XEN_SYSCTL_PHYSCAP_X86_ASSISTED_XAPIC and
>> XEN_SYSCTL_PHYSCAP_X86_ASSISTED_X2APIC to report accelerated xAPIC and
>> x2APIC, on x86 hardware. This is so that xAPIC and x2APIC virtualization
>> can subsequently be enabled on a per-domain basis.
>> 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 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>
>> Reviewed-by: "Roger Pau Monné" <roger....@citrix.com>
>> Reviewed-by: Jan Beulich <jbeul...@suse.com>
>> Reviewed-by: Anthony PERARD <anthony.per...@citrix.com>
>
> Could you please clarify whether you did drop Kevin's R-b (which, a
> little unhelpfully, he provided in reply to v9 a week after you had
> posted v10) because of ...
>
>> v10:
>> * Make assisted_x{2}apic_available conditional upon _vmx_cpu_up()
>
> ... this, requiring him to re-offer the tag? Until told otherwise I
> will assume so.It wasn't intentional but yes, that is right. There was a change, albeit minor, in vmx from v9 to v10 so I do require Kevin Tian or Jun Nakajima to review it. Thank you, Jane.
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