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[Qemu-devel] Re: [PATCH v3 12/21] kvm: x86: Drop MCE MSRs write back res
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH v3 12/21] kvm: x86: Drop MCE MSRs write back restrictions |
Date: |
Wed, 05 Jan 2011 10:06:22 +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 |
Am 05.01.2011 09:33, Huang Ying wrote:
> On Wed, 2011-01-05 at 16:07 +0800, Jan Kiszka wrote:
>> Am 05.01.2011 07:42, Huang Ying wrote:
>>> On Tue, 2011-01-04 at 16:32 +0800, Jan Kiszka wrote:
>>>> From: Jan Kiszka <address@hidden>
>>>>
>>>> There is no need to restrict writing back MCE MSRs to reset or full
>>>> state updates as setting their values has no side effects.
>>>
>>> Sorry for late.
>>
>> Don't worry.
>>
>>>
>>> The MCE MSRs contents is sticky for warm reset except MCG_STATUS, so
>>> their content should be kept. And the following sequence may set
>>> uncorrected value in MCE registers.
>>>
>>> savevm -> loadvm -> (OS clear MCE registers) -> reset -> (MCE registers
>>> has new (uncorrected) value)
>>
>> Sorry, I can't follow. Unless I miss some subtle detail, the question is
>> not when we transfer the mcg_* CPUState fields to the kernel, but when
>> and how we manipulate them in user space, e.g. on reset. Where are those
>> fields touched incorrectly between get and put msrs so that we cannot
>> write them back?
>
> If my understanding is correct, MSRs are not saved to user space
> (env->mce_banks) during reset in current code. So if all MCE MSRs are
> restored to kernel, their user space contents from previous loadvm may
> be put into kernel after reset.
Ah, good point! We need
diff --git a/vl.c b/vl.c
index 1958e01..23d4169 100644
--- a/vl.c
+++ b/vl.c
@@ -1353,6 +1353,7 @@ static void main_loop(void)
}
if (qemu_reset_requested()) {
pause_all_vcpus();
+ cpu_synchronize_all_states();
qemu_system_reset();
resume_all_vcpus();
}
and corresponding (sigh...) qemu-kvm patch. Will post them.
Jan
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- [Qemu-devel] [PATCH v3 08/21] kvm: x86: Remove redundant mp_state initialization, (continued)
- [Qemu-devel] [PATCH v3 08/21] kvm: x86: Remove redundant mp_state initialization, Jan Kiszka, 2011/01/04
- [Qemu-devel] [PATCH v3 04/21] kvm: Improve reporting of fatal errors, Jan Kiszka, 2011/01/04
- [Qemu-devel] [PATCH v3 09/21] kvm: x86: Fix xcr0 reset mismerge, Jan Kiszka, 2011/01/04
- [Qemu-devel] [PATCH v3 10/21] kvm: x86: Refactor msr_star/hsave_pa setup and checks, Jan Kiszka, 2011/01/04
- [Qemu-devel] [PATCH v3 11/21] kvm: x86: Reset paravirtual MSRs, Jan Kiszka, 2011/01/04
- [Qemu-devel] [PATCH v3 12/21] kvm: x86: Drop MCE MSRs write back restrictions, Jan Kiszka, 2011/01/04
[Qemu-devel] [PATCH v3 14/21] kvm: x86: Fix !CONFIG_KVM_PARA build, Jan Kiszka, 2011/01/04
[Qemu-devel] [PATCH v3 16/21] kvm: Drop smp_cpus argument from init functions, Jan Kiszka, 2011/01/04
[Qemu-devel] [PATCH v3 19/21] kvm: Flush coalesced mmio buffer on IO window exits, Jan Kiszka, 2011/01/04
[Qemu-devel] [PATCH v3 18/21] kvm: x86: Rework identity map and TSS setup for larger BIOS sizes, Jan Kiszka, 2011/01/04
[Qemu-devel] [PATCH v3 20/21] kvm: Do not use qemu_fair_mutex, Jan Kiszka, 2011/01/04
[Qemu-devel] [PATCH v3 15/21] kvm: x86: Introduce kvmclock device to save/restore its state, Jan Kiszka, 2011/01/04