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Date: Thu, 17 Jul 2014 17:22:06 +0800 From: Tang Chen <tangchen@...fujitsu.com> To: Gleb Natapov <gleb@...nel.org> CC: Jan Kiszka <jan.kiszka@....de>, <mtosatti@...hat.com>, <nadav.amit@...il.com>, <kvm@...r.kernel.org>, <laijs@...fujitsu.com>, <isimatu.yasuaki@...fujitsu.com>, <guz.fnst@...fujitsu.com>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 5/5] kvm, mem-hotplug: Do not pin apic access page in memory. Hi Gleb, Sorry for the delay. Please see below. On 07/15/2014 10:40 PM, Gleb Natapov wrote: ...... >>>> >>> We can request APIC_ACCESS_ADDR reload during L2->L1 vmexit emulation, so >>> if APIC_ACCESS_ADDR changes while L2 is running it will be reloaded for L1 too. >>> >> >> apic pages for L2 and L1 are not the same page, right ? >> > If L2 guest enable apic access page then they are different, otherwise > they are the same. > >> I think, just like we are doing in patch 5/5, we cannot wait for the next >> L2->L1 vmexit. >> We should enforce a L2->L1 vmexit in mmu_notifier, just like >> make_all_cpus_request() does. >> >> Am I right ? >> > I do not see why forcing APIC_ACCESS_ADDR reload during L2->L1 exit is not enough. Yes, you are right. APIC_ACCESS_ADDR reload should be done during L2->L1 vmexit. I mean, before the page is moved to other place, we have to enforce a L2->L1 vmexit, but not wait for the next L2->L1 vmexit. Since when the page is being moved, if the L2 vm is still running, it could access apic page directly. And the vm may corrupt. In the mmu_notifier called before the page is moved, we have to enforce a L2->L1 vmexit, and ask vcpus to reload APIC_ACCESS_ADDR for L2 vm. The process will wait till the page migration is completed, and update the APIC_ACCESS_ADDR, and re-enter guest mode. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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