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From: Gleb Natapov <gleb@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>,
	mtosatti@redhat.com, nadav.amit@gmail.com, jan.kiszka@web.de,
	kvm@vger.kernel.org, laijs@cn.fujitsu.com,
	isimatu.yasuaki@jp.fujitsu.com, guz.fnst@cn.fujitsu.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 4/7] kvm, mem-hotplug: Reload L1' apic access page on migration in vcpu_enter_guest().
Date: Thu, 11 Sep 2014 16:59:56 +0300	[thread overview]
Message-ID: <20140911135956.GC26540@minantech.com> (raw)
In-Reply-To: <54119E01.9000908@redhat.com>

On Thu, Sep 11, 2014 at 03:05:05PM +0200, Paolo Bonzini wrote:
> Il 11/09/2014 13:30, Gleb Natapov ha scritto:
> >> > +			vmcs_write64(APIC_ACCESS_ADDR, page_to_phys(page));
> >> > +			/*
> >> > +			 * Do not pin apic access page in memory so that memory
> >> > +			 * hotplug process is able to migrate it.
> >> > +			 */
> >> > +			put_page(page);
> >> >  		}
> > This code is in prepare_vmcs02() and is executed during L1->L2 vmentry. What happens
> > when apic access page is migrated while L2 is running? It needs to be update somewhere.
> 
> Before it is migrated, the MMU notifier is called and will force a
> vmexit on all CPUs.  The reload code will call GUP again on the page
> again and swap it in.
> 
This is how it will work without "if (!is_guest_mode(vcpu))". But,
unless I am missing something, with this check it will not work while
vcpu is in L2.

Suppose vmcs01->APIC_ACCESS_ADDR = 0xf000. During L2 entry
vmcs02->APIC_ACCESS_ADDR is set to 0xf000 too (by prepare_vmcs02). Now
0xf000 is migrated to 0x8000, mmu notifier is called, it forces vmexit,
but vcpu is in a guest mode so vmcs02->APIC_ACCESS_ADDR is never updated
to 0x8000 because of "if (!is_guest_mode(vcpu))" check. So what am I
missing here?

--
			Gleb.

  reply	other threads:[~2014-09-11 14:08 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-11  5:37 [PATCH v5 0/7] kvm, mem-hotplug: Do not pin ept identity pagetable and apic access page Tang Chen
2014-09-11  5:38 ` [PATCH v5 1/7] kvm: Use APIC_DEFAULT_PHYS_BASE macro as the apic access page address Tang Chen
2014-09-11  9:10   ` Paolo Bonzini
2014-09-11  5:38 ` [PATCH v5 2/7] kvm: Remove ept_identity_pagetable from struct kvm_arch Tang Chen
2014-09-11  9:14   ` Paolo Bonzini
2014-09-11  5:38 ` [PATCH v5 3/7] kvm: Make init_rmode_identity_map() return 0 on success Tang Chen
2014-09-11  9:17   ` Paolo Bonzini
2014-09-11 10:26     ` tangchen
2014-09-11  5:38 ` [PATCH v5 4/7] kvm, mem-hotplug: Reload L1' apic access page on migration in vcpu_enter_guest() Tang Chen
2014-09-11  9:21   ` Paolo Bonzini
2014-09-11 10:12     ` Gleb Natapov
2014-09-11 10:47       ` Paolo Bonzini
2014-09-11 11:30         ` Gleb Natapov
2014-09-11 13:05           ` Paolo Bonzini
2014-09-11 13:59             ` Gleb Natapov [this message]
2014-09-11 14:06               ` Paolo Bonzini
2014-09-11 14:21                 ` Gleb Natapov
2014-09-11 14:24                   ` Paolo Bonzini
2014-09-11 14:31                     ` Gleb Natapov
2014-09-11 14:37                       ` Paolo Bonzini
2014-09-11 14:47                         ` Gleb Natapov
2014-09-12  3:32                           ` tangchen
2014-09-12  3:36                     ` tangchen
2014-09-11 10:20     ` tangchen
2014-09-11 10:39       ` Paolo Bonzini
2014-09-11  5:38 ` [PATCH v5 5/7] kvm, mem-hotplug: Reload L1's apic access page on migration when L2 is running Tang Chen
2014-09-11  9:28   ` Paolo Bonzini
2014-09-11  5:38 ` [PATCH v5 6/7] kvm, mem-hotplug: Unpin and remove kvm_arch->apic_access_page Tang Chen
2014-09-11  9:34   ` Paolo Bonzini
2014-09-11  5:38 ` [PATCH v5 7/7] kvm, mem-hotplug: Unpin and remove nested_vmx->apic_access_page Tang Chen
2014-09-11  9:33   ` Paolo Bonzini
2014-09-11  9:43     ` tangchen

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