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[Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp |
Date: |
Thu, 04 Mar 2010 09:23:46 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Gleb Natapov wrote:
> On Thu, Mar 04, 2010 at 12:34:22AM +0100, Jan Kiszka wrote:
>> Gleb Natapov wrote:
>>> On Mon, Mar 01, 2010 at 06:17:22PM +0100, Jan Kiszka wrote:
>>>> As we hard-wire the BSP to CPU 0 anyway and cpuid_apic_id equals
>>>> cpu_index, cpu_is_bsp can also be based on the latter directly. This
>>>> will help an early user of it: KVM while initializing mp_state.
>>>>
>>>> Signed-off-by: Jan Kiszka <address@hidden>
>>>> ---
>>>> hw/pc.c | 3 ++-
>>>> 1 files changed, 2 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/hw/pc.c b/hw/pc.c
>>>> index b90a79e..58c32ea 100644
>>>> --- a/hw/pc.c
>>>> +++ b/hw/pc.c
>>>> @@ -767,7 +767,8 @@ static void pc_init_ne2k_isa(NICInfo *nd)
>>>>
>>>> int cpu_is_bsp(CPUState *env)
>>>> {
>>>> - return env->cpuid_apic_id == 0;
>>>> + /* We hard-wire the BSP to the first CPU. */
>>>> + return env->cpu_index == 0;
>>>> }
>>> We should not assume that. The function was written like that
>>> specifically so the code around it will not rely on this assumption.
>>> Now you change that specifically to write code that will do incorrect
>>> assumptions. I don't see the logic here.
>> The logic is that we do not support any other mapping yet - with or
>> without this change. Without it, we complicate the APIC initialization
>> for (so far) no good reason. Once we want to support different BSP
>> assignments, we need to go through the code and rework some parts anyway.
>>
> As far as I remember the only part that was missing was a command line to
> specify apic IDs for each CPU and what CPU is BSP. The code was ready
> otherwise. I's very sad if this was broken by other modifications. But
> changes like that actually pushes us back from our goal. Why not rework
> code so it will work with correct cpu_is_bsp() function instead of
> introducing this hack?
If you can confirm that there is a serious use case behind it, I will
look into this again. But so far, I did not find it.
Jan
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- [Qemu-devel] [PATCH v4 08/10] qemu-kvm: Clean up KVM's APIC hooks, (continued)
- [Qemu-devel] [PATCH v4 08/10] qemu-kvm: Clean up KVM's APIC hooks, Jan Kiszka, 2010/03/01
- [Qemu-devel] [PATCH v4 02/10] qemu-kvm: Rework VCPU state writeback API, Jan Kiszka, 2010/03/01
- [Qemu-devel] [PATCH v4 06/10] qemu-kvm: Use VCPU event state for reset and vmsave/load, Jan Kiszka, 2010/03/01
- [Qemu-devel] [PATCH v4 01/10] qemu-kvm: Add KVM_CAP_X86_ROBUST_SINGLESTEP-awareness, Jan Kiszka, 2010/03/01
- [Qemu-devel] [PATCH v4 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Jan Kiszka, 2010/03/01
- [Qemu-devel] [PATCH v4 10/10] qemu-kvm: Bring qemu_init_vcpu back home, Jan Kiszka, 2010/03/01
- [Qemu-devel] [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Jan Kiszka, 2010/03/01
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Gleb Natapov, 2010/03/03
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Jan Kiszka, 2010/03/03
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Gleb Natapov, 2010/03/04
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp,
Jan Kiszka <=
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Gleb Natapov, 2010/03/04
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Jan Kiszka, 2010/03/04
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Gleb Natapov, 2010/03/04
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Gleb Natapov, 2010/03/07
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Jan Kiszka, 2010/03/07
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Jan Kiszka, 2010/03/07
- [Qemu-devel] Re: [PATCH v4 03/10] x86: Extend validity of cpu_is_bsp, Gleb Natapov, 2010/03/07
[Qemu-devel] Re: [PATCH v4 00/10] qemu-kvm: Hook cleanups and yet more use of upstream code, Jan Kiszka, 2010/03/01
[Qemu-devel] Re: [PATCH v4 00/10] qemu-kvm: Hook cleanups and yet more use of upstream code, Marcelo Tosatti, 2010/03/01