From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Juergen Gross <JGross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>,
David Vrabel <david.vrabel@citrix.com>,
"H. Peter Anvin" <hpa@zytor.com>,
xen-devel@lists.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping
Date: Thu, 30 Jun 2016 03:10:11 -0600 [thread overview]
Message-ID: <5774FE1302000078000F9FED@prv-mh.provo.novell.com> (raw)
In-Reply-To: <5040c916-279f-c350-383a-583ec1700686@citrix.com>
>>> On 29.06.16 at 18:27, <andrew.cooper3@citrix.com> wrote:
> On 29/06/16 17:19, Vitaly Kuznetsov wrote:
>> To explain better what I'm trying to suggest here please take a look at
>> the attached patch. If we can guarantee long term that ACPI id always
>> equals to Xen's idea of vCPU id this is probably the easiest way.
>>
>> -- Vitaly
>
> The code in hvmloader which sets up the MADT does:
>
> for ( i = 0; i < hvm_info->nr_vcpus; i++ )
> {
> memset(lapic, 0, sizeof(*lapic));
> lapic->type = ACPI_PROCESSOR_LOCAL_APIC;
> lapic->length = sizeof(*lapic);
> /* Processor ID must match processor-object IDs in the DSDT. */
> lapic->acpi_processor_id = i;
> lapic->apic_id = LAPIC_ID(i);
> lapic->flags = (test_bit(i, hvm_info->vcpu_online)
> ? ACPI_LOCAL_APIC_ENABLED : 0);
> lapic++;
> }
>
> So relying on the acpi_processor_id does look to be reliable. That code
> hasn't changed since 2007, and that was only a bugfix. I would go so
> far as to say it is reasonable for us to guarantee this in the guest ABI.
In fact - is there any other way a guest could learn the vCPU IDs
of its CPUs in a reliable way? I don't think so, and hence this de
facto already is part of the ABI; we should of course spell it out
somewhere.
Jan
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next prev parent reply other threads:[~2016-06-30 9:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1467132449-1030-1-git-send-email-vkuznets@redhat.com>
2016-06-28 16:47 ` [PATCH linux 1/8] x86/xen: update cpuid.h from Xen-4.7 Vitaly Kuznetsov
2016-06-28 16:47 ` [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Vitaly Kuznetsov
2016-06-28 17:28 ` Andrew Cooper
[not found] ` <c16250fe-28a4-20d6-2c47-6c2d3cae85ff@citrix.com>
2016-06-29 12:16 ` Vitaly Kuznetsov
2016-06-29 12:30 ` Andrew Cooper
[not found] ` <689743e6-0b0e-9935-58e1-2dfa257c7bf8@citrix.com>
2016-06-29 12:50 ` Vitaly Kuznetsov
[not found] ` <87oa6kupko.fsf@vitty.brq.redhat.com>
2016-06-29 16:19 ` Vitaly Kuznetsov
2016-06-29 16:27 ` Andrew Cooper
2016-06-30 9:10 ` Jan Beulich [this message]
2016-07-01 12:06 ` Vitaly Kuznetsov
2016-07-01 13:33 ` Jan Beulich
2016-07-05 15:34 ` Konrad Rzeszutek Wilk
2016-07-05 15:44 ` Jan Beulich
[not found] ` <577BF1FC02000078000FB51A@prv-mh.provo.novell.com>
2016-07-07 10:15 ` Joao Martins
2016-06-28 16:47 ` [PATCH linux 3/8] x86/xen: use xen_vcpu_id mapping for HYPERVISOR_vcpu_op Vitaly Kuznetsov
2016-06-29 12:26 ` David Vrabel
2016-06-28 16:47 ` [PATCH linux 4/8] x86/xen: use xen_vcpu_id mapping when pointing vcpu_info to the shared_info page Vitaly Kuznetsov
2016-06-29 12:32 ` David Vrabel
2016-06-28 16:47 ` [PATCH linux 5/8] xen/events: use xen_vcpu_id mapping in events_base Vitaly Kuznetsov
2016-06-28 16:47 ` [PATCH linux 6/8] xen/events: fifo: use xen_vcpu_id mapping Vitaly Kuznetsov
2016-06-28 16:47 ` [PATCH linux 7/8] xen/evtchn: " Vitaly Kuznetsov
2016-06-28 16:47 ` [PATCH linux 8/8] xen/pvhvm: run xen_vcpu_setup() for the boot CPU Vitaly Kuznetsov
2016-06-28 17:32 ` [PATCH linux 0/8] xen: pvhvm: support bootup on secondary vCPUs David Vrabel
[not found] ` <5772B4C2.4010906@citrix.com>
2016-06-29 9:16 ` Vitaly Kuznetsov
[not found] ` <871t3gwe0o.fsf@vitty.brq.redhat.com>
2016-06-29 12:36 ` David Vrabel
[not found] ` <5773C0DF.3090905@citrix.com>
2016-07-01 9:24 ` Vitaly Kuznetsov
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