From: Jan Kiszka <jan.kiszka@siemens.com>
To: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 04/19] qemu-kvm: x86: Drop MSR reset
Date: Thu, 05 May 2011 10:27:46 +0200 [thread overview]
Message-ID: <4DC25F82.2040501@siemens.com> (raw)
In-Reply-To: <4DC25CDB.9060805@redhat.com>
On 2011-05-05 10:16, Avi Kivity wrote:
> On 05/05/2011 11:11 AM, Jan Kiszka wrote:
>> On 2011-05-05 10:08, Avi Kivity wrote:
>>> On 05/04/2011 10:43 PM, Jan Kiszka wrote:
>>>> From: Jan Kiszka<jan.kiszka@siemens.com>
>>>>
>>>> Paravirtual MSRs are properly cleared on reset now, and blindly clearing
>>>> the rest is questionable anyway (better address those one by one,
>>>> re-initializing their backing CPU state fields).
>>>>
>>>
>>> This can introduce a regression when new paravirtual MSRs are added.
>>
>> You mean MSRs already included or future ones?
>
> Future ones.
>
>>> So
>>> we either need to port this, or query the reset state from the kernel
>>> immediately after creating the vcpu and saving it.
>>
>> Can't completely follow what you mean.
>>
>> My general point remains: Every MSR requires individual care, not blind
>> overwriting like qemu-kvm does. So the person contributing a new MSR,
>> real or pv, has to tackle this aspect, and we need to review the code in
>> this regard.
>
> It's a trick to avoid needing individual care.
>
> 1. Call KVM_CREATE_VCPU. This causes all MSRs to be initialized to
> their power-on reset values.
Almost all: Which ones are CPU specific like the APIC_BASE?
> 2. Issue KVM_GET_MSR_LIST, and then KVM_GET_MSRS to read all MSRs.
> Stash them all in safe places - the ones known to qemu but also the
> unknown ones. Qemu may use its own values for the MSRs it knows about
> (for example if different cpu models have different power-on values)
> 3. On reset, issue KVM_SET_MSRS with the MSR values obtained in step 2.
>
> The result is forward and backwards compatibility without lockstepping
> qemu and kvm.
OK, sounds good. I will work out a patch for uq/master.
Nevertheless, the qemu-kvm code is already unneeded today and can safely
be removed IMHO.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
next prev parent reply other threads:[~2011-05-05 8:27 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 19:43 [PATCH 00/19] qemu-kvm: Cleanup and switch to upstream - Part I Jan Kiszka
2011-05-04 19:43 ` [PATCH 01/19] qemu-kvm: Switch to upstream mp_state functions Jan Kiszka
2011-05-04 19:43 ` [PATCH 02/19] qemu-kvm: x86: Use upstream kvmclock device Jan Kiszka
2011-05-04 19:43 ` [PATCH 03/19] Revert "introduce VMSTATE_U64" Jan Kiszka
2011-05-04 19:43 ` [PATCH 04/19] qemu-kvm: x86: Drop MSR reset Jan Kiszka
2011-05-05 8:08 ` Avi Kivity
2011-05-05 8:11 ` Jan Kiszka
2011-05-05 8:16 ` Avi Kivity
2011-05-05 8:27 ` Jan Kiszka [this message]
2011-05-05 8:33 ` Avi Kivity
2011-05-05 8:44 ` Jan Kiszka
2011-05-05 8:53 ` Avi Kivity
2011-05-05 9:32 ` Jan Kiszka
2011-05-05 10:22 ` Avi Kivity
2011-05-05 10:36 ` Jan Kiszka
2011-05-05 11:57 ` Avi Kivity
2011-05-05 11:22 ` Gleb Natapov
2011-05-05 11:58 ` Avi Kivity
2011-05-05 12:23 ` Gleb Natapov
2011-05-05 12:42 ` Jan Kiszka
2011-05-05 13:33 ` Marcelo Tosatti
2011-05-05 18:08 ` Gleb Natapov
2011-05-04 19:43 ` [PATCH 05/19] qemu-kvm: Use upstream VCPU reset services Jan Kiszka
2011-05-04 19:43 ` [PATCH 06/19] qemu-kvm: Use upstream vcpu initialization Jan Kiszka
2011-05-04 19:43 ` [PATCH 07/19] qemu-kvm: Start using qemu-thread services Jan Kiszka
2011-05-04 19:43 ` [PATCH 08/19] qemu-kvm: Use upstream kvm_arch_get/put_registers Jan Kiszka
2011-05-04 19:43 ` [PATCH 09/19] qemu-kvm: Use upstream state synchronization services Jan Kiszka
2011-05-04 19:43 ` [PATCH 10/19] qemu-kvm: Drop remaining libkvm fragments Jan Kiszka
2011-05-04 19:43 ` [PATCH 11/19] qemu-kvm: Drop some more unused code Jan Kiszka
2011-05-04 19:43 ` [PATCH 12/19] qemu-kvm: Drop some obsolete/unused fields from kvm_context Jan Kiszka
2011-05-04 19:43 ` [PATCH 13/19] qemu-kvm: Refactor in-kernel irqchip and pit control Jan Kiszka
2011-05-04 19:43 ` [PATCH 14/19] qemu-kvm: Fold kvm_create into kvm_create_context Jan Kiszka
2011-05-04 19:43 ` [PATCH 15/19] qemu-kvm: Fold kvm_arch_qemu_create_context into kvm_arch_create Jan Kiszka
2011-05-04 19:43 ` [PATCH 16/19] qemu-kvm: Push PIT reinjection control into x86 code Jan Kiszka
2011-05-04 19:43 ` [PATCH 17/19] qemu-kvm: Replace kvm_show_regs/code with cpu_dump_state Jan Kiszka
2011-05-04 19:43 ` [PATCH 18/19] qemu-kvm: Fold kvm_init_coalesced_mmio into kvm_create_context Jan Kiszka
2011-05-04 19:43 ` [PATCH 19/19] qemu-kvm: x86: Use kvm_arch_init Jan Kiszka
2011-05-05 8:22 ` [PATCH 00/19] qemu-kvm: Cleanup and switch to upstream - Part I Avi Kivity
2011-05-05 8:29 ` Jan Kiszka
2011-05-06 13:51 ` Marcelo Tosatti
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