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Groups > linux.kernel > #1433703
| From | Vitaly Kuznetsov <vkuznets@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping |
| Date | 2016-06-29 14:20 +0200 |
| Message-ID | <rPmDf-44F-15@gated-at.bofh.it> (permalink) |
| References | <rP4n0-157-17@gated-at.bofh.it> <rP4n0-157-35@gated-at.bofh.it> <rP4ZI-1y6-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Andrew Cooper <andrew.cooper3@citrix.com> writes:
> On 28/06/16 17:47, Vitaly Kuznetsov wrote:
>> @@ -1808,6 +1822,8 @@ static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
>> int cpu = (long)hcpu;
>> switch (action) {
>> case CPU_UP_PREPARE:
>> + /* vLAPIC_ID == Xen's vCPU_ID * 2 for HVM guests */
>> + per_cpu(xen_vcpu_id, cpu) = cpu_physical_id(cpu) / 2;
>
> Please do not assume or propagate this brokenness. It is incorrect in
> the general case, and I will be fixing in the hypervisor in due course.
>
> Always read the APIC_ID from the LAPIC, per regular hardware.
(I'm probbaly missing something important - please bear with me)
The problem here is that I need to get _other_ CPU's id before any code
is executed on that CPU (or, at least, this is the current state of
affairs if you look at xen_hvm_cpu_up()) so I can't use CPUID/do MSR
reads/... The only option I see here is to rely on ACPI (MADT) data
which is stored in x86_cpu_to_apicid (and that's what cpu_physical_id()
gives us). MADT also has processor id which connects it to DSDT but I'm
not sure Linux keeps this data. But this is something fixable I guess.
--
Vitaly
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[PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-06-28 18:50 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Andrew Cooper <andrew.cooper3@citrix.com> - 2016-06-28 19:30 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-06-29 14:20 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Andrew Cooper <andrew.cooper3@citrix.com> - 2016-06-29 14:40 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-06-29 15:00 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-06-29 18:30 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping "Jan Beulich" <JBeulich@suse.com> - 2016-06-30 11:20 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-07-01 14:10 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping "Jan Beulich" <JBeulich@suse.com> - 2016-07-01 16:00 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2016-07-05 17:40 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping "Jan Beulich" <JBeulich@suse.com> - 2016-07-05 17:50 +0200
Re: [Xen-devel] [PATCH linux 2/8] xen: introduce xen_vcpu_id mapping Joao Martins <joao.m.martins@oracle.com> - 2016-07-07 12:20 +0200
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