From: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
To: Gleb Natapov <gleb@redhat.com>
Cc: Avi Kivity <avi@redhat.com>, kvm@vger.kernel.org
Subject: Re: [PATCH 22/24] KVM: x86 emulator: restart string instruction without going back to a guest.
Date: Wed, 10 Mar 2010 18:12:34 +0900 [thread overview]
Message-ID: <4B976282.7020108@oss.ntt.co.jp> (raw)
In-Reply-To: <20100310090633.GS16909@redhat.com>
Gleb Natapov wrote:
> On Wed, Mar 10, 2010 at 11:30:20AM +0900, Takuya Yoshikawa wrote:
>> Gleb Natapov wrote:
>>> On Tue, Mar 09, 2010 at 04:50:29PM +0200, Avi Kivity wrote:
>>>> On 03/09/2010 04:09 PM, Gleb Natapov wrote:
>>>>> Currently when string instruction is only partially complete we go back
>>>>> to a guest mode, guest tries to reexecute instruction and exits again
>>>>> and at this point emulation continues. Avoid all of this by restarting
>>>>> instruction without going back to a guest mode.
>>>> What happens if rcx is really big? Going back into the guest gave
>>>> us a preemption point.
>>>>
>>> Two solutions. We can check if reschedule is required and yield cpu if
>>> needed. Or we can enter guest from time to time.
>> One generic question: from the viewpoint of KVM's policy, is it OK to make
>> the semantics different from real CPUs?
>>
>> Semantics, may be better to use other words, but I'm little bit worried that
>> the second solution may change something, not mentioning about bugs but some
>> behavior patterns depending on the "time to time".
>>
> Entering guest from time to time will not change semantics of the
> processor (if code is not modified under processor's feet at least).
> Currently we reenter guest mode after each iteration of string
> instruction for all instruction but ins/outs.
>
E.g., is there no chance that during the repetitions, in the middle of the
repetitions, page faults occur? If it can, without entering the guest, can
we handle it?
-- I lack some basic assumptions?
> --
> Gleb.
> --
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next prev parent reply other threads:[~2010-03-10 9:10 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-09 14:08 [PATCH 00/24] [RFC] emulator cleanup Gleb Natapov
2010-03-09 14:08 ` [PATCH 01/24] KVM: Remove pointer to rflags from realmode_set_cr parameters Gleb Natapov
2010-03-09 14:09 ` [PATCH 02/24] KVM: Provide callback to get/set control registers in emulator ops Gleb Natapov
2010-03-09 14:18 ` Avi Kivity
2010-03-09 14:24 ` Gleb Natapov
2010-03-09 14:09 ` [PATCH 03/24] KVM: remove realmode_lmsw function Gleb Natapov
2010-03-09 14:09 ` [PATCH 04/24] KVM: Provide current CPL as part of emulator context Gleb Natapov
2010-03-09 14:24 ` Avi Kivity
2010-03-09 14:27 ` Gleb Natapov
2010-03-09 14:09 ` [PATCH 05/24] KVM: Provide current eip " Gleb Natapov
2010-03-09 14:09 ` [PATCH 06/24] KVM: x86 emulator: fix mov r/m, sreg emulation Gleb Natapov
2010-03-09 14:09 ` [PATCH 07/24] KVM: x86 emulator: fix 0f 01 /5 emulation Gleb Natapov
2010-03-09 14:27 ` Avi Kivity
2010-03-09 14:33 ` Gleb Natapov
2010-03-09 14:34 ` Avi Kivity
2010-03-09 14:09 ` [PATCH 08/24] KVM: x86 emulator: 0f (20|21|22|23) ignore mod bits Gleb Natapov
2010-03-09 14:09 ` [PATCH 09/24] KVM: x86 emulator: inject #UD on access to non-existing CR Gleb Natapov
2010-03-09 14:09 ` [PATCH 10/24] KVM: x86 emulator: fix mov dr to inject #UD when needed Gleb Natapov
2010-03-09 14:09 ` [PATCH 11/24] KVM: x86 emulator: fix return values of syscall/sysenter/sysexit emulations Gleb Natapov
2010-03-09 14:09 ` [PATCH 12/24] KVM: x86 emulator: do not call writeback if msr access fails Gleb Natapov
2010-03-09 14:09 ` [PATCH 13/24] KVM: x86 emulator: If LOCK prefix is used dest arg should be memory Gleb Natapov
2010-03-09 14:09 ` [PATCH 14/24] KVM: x86 emulator: cleanup grp3 return value Gleb Natapov
2010-03-09 14:09 ` [PATCH 15/24] KVM: x86 emulator: Provide more callbacks for x86 emulator Gleb Natapov
2010-03-09 14:43 ` Avi Kivity
2010-03-09 16:25 ` Gleb Natapov
2010-03-09 17:22 ` Avi Kivity
2010-03-09 17:57 ` Gleb Natapov
2010-03-10 9:11 ` Avi Kivity
2010-03-09 14:09 ` [PATCH 16/24] KVM: x86 emulator: Emulate task switch in emulator.c Gleb Natapov
2010-03-09 14:09 ` [PATCH 17/24] KVM: x86 emulator: Use load_segment_descriptor() instead of kvm_load_segment_descriptor() Gleb Natapov
2010-03-09 14:09 ` [PATCH 18/24] KVM: Use task switch from emulator.c Gleb Natapov
2010-03-09 14:09 ` [PATCH 19/24] KVM: x86 emulator: fix in/out emulation Gleb Natapov
2010-03-09 14:47 ` Avi Kivity
2010-03-09 18:09 ` Gleb Natapov
2010-03-10 9:12 ` Avi Kivity
2010-03-10 14:41 ` Gleb Natapov
2010-03-09 14:09 ` [PATCH 20/24] KVM: x86 emulator: Move string pio emulation into emulator.c Gleb Natapov
2010-03-09 14:09 ` [PATCH 21/24] KVM: x86 emulator: remove saved_eip Gleb Natapov
2010-03-09 14:09 ` [PATCH 22/24] KVM: x86 emulator: restart string instruction without going back to a guest Gleb Natapov
2010-03-09 14:50 ` Avi Kivity
2010-03-09 18:11 ` Gleb Natapov
2010-03-10 2:30 ` Takuya Yoshikawa
2010-03-10 9:06 ` Gleb Natapov
2010-03-10 9:12 ` Takuya Yoshikawa [this message]
2010-03-10 9:14 ` Avi Kivity
2010-03-10 9:15 ` Gleb Natapov
2010-03-10 10:08 ` Takuya Yoshikawa
2010-03-10 13:48 ` Gleb Natapov
2010-03-11 9:58 ` Takuya Yoshikawa
2010-03-11 10:07 ` Gleb Natapov
2010-03-10 9:13 ` Avi Kivity
2010-03-09 14:09 ` [PATCH 23/24] KVM: x86 emulator: introduce pio in string read ahead Gleb Natapov
2010-03-09 14:09 ` [PATCH 24/24] KVM: small kvm_arch_vcpu_ioctl_run() cleanup Gleb Natapov
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