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Re: [PATCH RESEND v10 1/2] xen+tools: Report Interrupt Controller Virtualization capabilities on x86


  • To: Jan Beulich <jbeulich@xxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>
  • From: Jane Malalane <Jane.Malalane@xxxxxxxxxx>
  • Date: Wed, 29 Jun 2022 15:16:30 +0000
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  • Cc: George Dunlap <George.Dunlap@xxxxxxxxxx>, Nick Rosbrook <rosbrookn@xxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Anthony Perard <anthony.perard@xxxxxxxxxx>, Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Christian Lindig <christian.lindig@xxxxxxxxxx>, David Scott <dave@xxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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  • Thread-topic: [PATCH RESEND v10 1/2] xen+tools: Report Interrupt Controller Virtualization capabilities on x86

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.cooper3@xxxxxxxxxx>
>> Signed-off-by: Jane Malalane <jane.malalane@xxxxxxxxxx>
>> Reviewed-by: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> 
> 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.

<<attachment: winmail.dat>>


 


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