From: Paolo Bonzini <pbonzini@redhat.com>
To: "Radim Krčmář" <rkrcmar@redhat.com>,
"Yang Zhang" <yang.zhang.wz@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, "Lan,
Tianyu" <tianyu.lan@intel.com>,
Igor Mammedov <imammedo@redhat.com>,
Jan Kiszka <jan.kiszka@web.de>, Peter Xu <peterx@redhat.com>
Subject: Re: [PATCH v2 04/13] KVM: x86: dynamic kvm_apic_map
Date: Mon, 11 Jul 2016 16:14:46 +0200 [thread overview]
Message-ID: <6dda9370-e538-2c7c-e95e-b6a6f1518bbf@redhat.com> (raw)
In-Reply-To: <20160711134837.GD21976@potion>
On 11/07/2016 15:48, Radim Krčmář wrote:
>>> I guess the easiest solution is to replace kvm_apic_id with a field in
>>> struct kvm_lapic, which is already shifted right by 24 in xAPIC mode.
>
> (I guess the fewest LOC is to look at vcpu->vcpu_id, which is equal to
> x2apic id. xapic id cannot be greater than 255 and all of those are
> covered by the initial value of max_id.)
Yes, this would work too. Or even better perhaps, look at vcpu->vcpu_id
in kvm_apic_id?
>> Or we can just simply put the assignment of apic_base to the end.
>
> Yes, this would work, I'd also remove recalculates from
> kvm_apic_set_*apic_id() and add a compiler barrier with comment for good
> measure, even though set_virtual_x2apic_mode() serves as one.
Why a compiler barrier?
> (What makes a bit wary is that it doesn't avoid the same problem if we
> changed KVM to reset apic id to xapic id first when disabling apic.)
Yes, this is why I prefer it fixed once and for all in kvm_apic_id...
> Races in recalculation and APIC ID changes also lead to invalid physical
> maps, which haven't been taken care of properly ...
Hmm, true, but can be fixed separately. Probably the mutex should be
renamed so that it can be taken outside recalculate_apic_map...
Paolo
> Having apic id stored in big endian, or "0-7,8-31" format, would be
> safest. I wanted to change the apic map to do incremental updates with
> with respect to the APIC that has changed, instead of being completely
> recomputed, so maybe the time is now. :)
>
next prev parent reply other threads:[~2016-07-11 14:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-07 17:15 [PATCH v2 00/13] KVM: x86: break the xAPIC barrier Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 01/13] KVM: x86: bump KVM_SOFT_MAX_VCPUS to 240 Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 02/13] KVM: x86: add kvm_apic_map_get_dest_lapic Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 03/13] KVM: x86: use physical LAPIC array for logical x2APIC Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 04/13] KVM: x86: dynamic kvm_apic_map Radim Krčmář
2016-07-11 6:07 ` Yang Zhang
2016-07-11 7:43 ` Paolo Bonzini
2016-07-11 10:14 ` Yang Zhang
2016-07-11 13:48 ` Radim Krčmář
2016-07-11 14:14 ` Paolo Bonzini [this message]
2016-07-11 15:52 ` Radim Krčmář
2016-07-11 16:04 ` Paolo Bonzini
2016-07-12 3:27 ` Yang Zhang
2016-07-07 17:15 ` [PATCH v2 05/13] KVM: x86: use generic function for MSI parsing Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 06/13] KVM: x86: use hardware-compatible format for APIC ID register Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 07/13] KVM: x86: reset APIC ID when enabling LAPIC Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 08/13] KVM: VMX: optimize APIC ID read with APICv Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 09/13] KVM: x86: reset lapic base in kvm_lapic_reset Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 10/13] KVM: pass struct kvm to kvm_set_routing_entry Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 11/13] KVM: x86: add KVM_CAP_X2APIC_API Radim Krčmář
2016-07-11 6:06 ` Yang Zhang
2016-07-11 7:44 ` Paolo Bonzini
2016-07-11 8:56 ` Yang Zhang
2016-07-11 9:17 ` Paolo Bonzini
2016-07-11 10:33 ` Yang Zhang
2016-07-11 10:40 ` Paolo Bonzini
2016-07-07 17:15 ` [PATCH v2 12/13] KVM: x86: bump MAX_VCPUS to 288 Radim Krčmář
2016-07-07 17:15 ` [PATCH v2 13/13] KVM: x86: bump KVM_MAX_VCPU_ID to 1023 Radim Krčmář
2016-07-08 10:00 ` [PATCH v2 00/13] KVM: x86: break the xAPIC barrier Paolo Bonzini
2016-07-08 16:29 ` Radim Krčmář
2016-07-08 16:30 ` Paolo Bonzini
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