From: Min-gyu Kim <mingyu84.kim@samsung.com>
To: 'Christoffer Dall' <c.dall@virtualopensystems.com>
Cc: android-virt@lists.cs.columbia.edu, kvm@vger.kernel.org,
tech@virtualopensystems.com, '김창환' <changhwan.m.kim@samsung.com>
Subject: RE: [PATCH v9 13/16] ARM: KVM: Emulation framework and CP15 emulation
Date: Tue, 17 Jul 2012 19:54:20 +0900 [thread overview]
Message-ID: <000601cd640a$855679e0$90036da0$@samsung.com> (raw)
In-Reply-To: <CANM98qLVY9o7=OGHRtfR8MGp1CTgQx7_L94nj581kUjghuQo3g@mail.gmail.com>
Why does the cache operation need to happen on the same CPU while the L1 caches between cores are coherent?
As you know, cache operations usually operate for a range and it iterates without disabling preemption.
Therefore, though you enclose the vcpu_run and handle_exit with preemption disable, the operations on a range can run on several cores.
If data of address X is written from CPU0 and CPU1 executes cache flush on address X while those 2 CPUs have same TTBR, does the cache operation fail? It seems to succeed from the document from ARM that I referred before. And that's why I think the preemption disable is unnecessary.
Regards
Kim, Min-gyu
-----Original Message-----
> And you said the reason of disabling preemption as CPU-specific data such as caches.
> But as far as I know, the l1 caches are coherent.
> (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0438e/
> BABFHDFE.html)
>
> Can you please explain why preemption disable is necessary in detail?
>
if a VM tries to do a cache maintenance operation specific to that CPU that traps we want to make sure that the emulation of such operations happen on the same physical CPU to ensure correct semantics.
-Christoffer
next prev parent reply other threads:[~2012-07-17 10:54 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-03 8:59 [PATCH v9 00/16] KVM/ARM Implementation Christoffer Dall
2012-07-03 8:59 ` [PATCH v9 01/16] ARM: add mem_type prot_pte accessor Christoffer Dall
2012-07-20 14:54 ` Andreas Färber
2012-07-26 21:26 ` Christoffer Dall
2012-07-03 8:59 ` [PATCH v9 02/16] ARM: Add config option ARM_VIRT_EXT Christoffer Dall
2012-07-03 8:59 ` [PATCH v9 03/16] ARM: Section based HYP idmap Christoffer Dall
2012-07-03 8:59 ` [PATCH v9 04/16] KVM: Move KVM_IRQ_LINE to arch-generic code Christoffer Dall
2012-07-03 19:50 ` Marcelo Tosatti
2012-07-24 12:37 ` Christoffer Dall
2012-07-03 9:00 ` [PATCH v9 05/16] KVM: Guard mmu_notifier specific code with CONFIG_MMU_NOTIFIER Christoffer Dall
2012-07-03 9:00 ` [PATCH v9 06/16] ARM: KVM: Initial skeleton to compile KVM support Christoffer Dall
2012-07-03 9:00 ` [PATCH v9 07/16] ARM: KVM: Support Cortex-A15 VCPUs reset Christoffer Dall
2012-07-03 9:00 ` [PATCH v9 08/16] ARM: KVM: Hypervisor inititalization Christoffer Dall
2012-07-03 9:00 ` [PATCH v9 09/16] ARM: KVM: Module unloading support Christoffer Dall
2012-07-03 9:01 ` [PATCH v9 10/16] ARM: KVM: Memory virtualization setup Christoffer Dall
2012-07-03 9:01 ` [PATCH v9 11/16] ARM: KVM: Inject IRQs and FIQs from userspace Christoffer Dall
2012-08-06 17:20 ` [Android-virt] " Peter Maydell
2012-08-07 13:59 ` Avi Kivity
2012-08-07 14:12 ` Peter Maydell
2012-08-07 14:28 ` Avi Kivity
2012-08-07 14:36 ` Peter Maydell
2012-07-03 9:01 ` [PATCH v9 12/16] ARM: KVM: World-switch implementation Christoffer Dall
2012-07-03 10:07 ` Avi Kivity
2012-07-25 14:16 ` Christoffer Dall
2012-07-03 9:01 ` [PATCH v9 13/16] ARM: KVM: Emulation framework and CP15 emulation Christoffer Dall
2012-07-12 5:35 ` 김민규
2012-07-16 14:09 ` Christoffer Dall
2012-07-17 10:54 ` Min-gyu Kim [this message]
2012-07-03 9:01 ` [PATCH v9 14/16] ARM: KVM: Handle guest faults in KVM Christoffer Dall
2012-07-03 9:02 ` [PATCH v9 15/16] ARM: KVM: Handle I/O aborts Christoffer Dall
2012-07-03 9:02 ` [PATCH v9 16/16] ARM: KVM: Guest wait-for-interrupts (WFI) support Christoffer Dall
2012-07-03 13:10 ` Avi Kivity
2012-07-03 13:14 ` [Android-virt] " Peter Maydell
2012-07-03 13:24 ` Avi Kivity
2012-07-03 13:49 ` Peter Maydell
2012-07-03 15:57 ` Avi Kivity
2012-07-26 21:08 ` Christoffer Dall
2012-07-03 13:29 ` [PATCH v9 00/16] KVM/ARM Implementation Avi Kivity
2012-07-03 13:51 ` [Android-virt] " Peter Maydell
2012-07-26 21:15 ` Christoffer Dall
2012-07-26 21:21 ` Peter Maydell
2012-07-26 21:25 ` Christoffer Dall
2012-07-03 19:51 ` Marcelo Tosatti
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