kernel.git/arch/arm/kvm, branch linux-3.15.y

arm: KVM: fix possible misalignment of PGDs and bounce page

2014-04-28T10:21:48Z

The kvm/mmu code shared by arm and arm64 uses kalloc() to allocate a bounce page (if hypervisor init code crosses page boundary) and hypervisor PGDs. The problem is that kalloc() does not guarantee the proper alignment. In the case of the bounce page, the page sized buffer allocated may also cross a page boundary negating the purpose and leading to a hang during kvm initialization. Likewise the PGDs allocated may not meet the minimum alignment requirements of the underlying MMU. This patch uses __get_free_page() to guarantee the worst case alignment needs of the bounce page and PGDs on both arm and arm64. Cc: # 3.10+ Signed-off-by: Mark Salter Acked-by: Marc Zyngier Signed-off-by: Christoffer Dall

ARM: KVM: disable KVM in Kconfig on big-endian systems

2014-04-26T11:20:03Z

KVM currently crashes and burns on big-endian hosts, so don't allow it to be selected until we've got that fixed. Cc: Marc Zyngier Signed-off-by: Will Deacon Signed-off-by: Christoffer Dall

Merge tag 'cpu-hotplug-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2014-04-07T21:55:46Z

Pull CPU hotplug notifiers registration fixes from Rafael Wysocki: "The purpose of this single series of commits from Srivatsa S Bhat (with a small piece from Gautham R Shenoy) touching multiple subsystems that use CPU hotplug notifiers is to provide a way to register them that will not lead to deadlocks with CPU online/offline operations as described in the changelog of commit 93ae4f978ca7f ("CPU hotplug: Provide lockless versions of callback registration functions"). The first three commits in the series introduce the API and document it and the rest simply goes through the users of CPU hotplug notifiers and converts them to using the new method" * tag 'cpu-hotplug-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (52 commits) net/iucv/iucv.c: Fix CPU hotplug callback registration net/core/flow.c: Fix CPU hotplug callback registration mm, zswap: Fix CPU hotplug callback registration mm, vmstat: Fix CPU hotplug callback registration profile: Fix CPU hotplug callback registration trace, ring-buffer: Fix CPU hotplug callback registration xen, balloon: Fix CPU hotplug callback registration hwmon, via-cputemp: Fix CPU hotplug callback registration hwmon, coretemp: Fix CPU hotplug callback registration thermal, x86-pkg-temp: Fix CPU hotplug callback registration octeon, watchdog: Fix CPU hotplug callback registration oprofile, nmi-timer: Fix CPU hotplug callback registration intel-idle: Fix CPU hotplug callback registration clocksource, dummy-timer: Fix CPU hotplug callback registration drivers/base/topology.c: Fix CPU hotplug callback registration acpi-cpufreq: Fix CPU hotplug callback registration zsmalloc: Fix CPU hotplug callback registration scsi, fcoe: Fix CPU hotplug callback registration scsi, bnx2fc: Fix CPU hotplug callback registration scsi, bnx2i: Fix CPU hotplug callback registration ...

arm, kvm: Fix CPU hotplug callback registration

2014-03-20T12:43:41Z

On 03/15/2014 12:40 AM, Christoffer Dall wrote: > On Fri, Mar 14, 2014 at 11:13:29AM +0530, Srivatsa S. Bhat wrote: >> On 03/13/2014 04:51 AM, Christoffer Dall wrote: >>> On Tue, Mar 11, 2014 at 02:05:38AM +0530, Srivatsa S. Bhat wrote: >>>> Subsystems that want to register CPU hotplug callbacks, as well as perform >>>> initialization for the CPUs that are already online, often do it as shown >>>> below: >>>> [...] >>> Just so we're clear, the existing code was simply racy as not prone to >>> deadlocks, right? >>> >>> This makes it clear that the test above for compatible CPUs can be quite >>> easily evaded by using CPU hotplug, but we don't really have a good >>> solution for handling that yet... Hmmm, grumble grumble, I guess if you >>> hotplug unsupported CPUs on a KVM/ARM system for now, stuff will break. >>> >> >> In this particular case, there was no deadlock possibility, rather the >> existing code had insufficient synchronization against CPU hotplug. >> >> init_hyp_mode() would invoke cpu_init_hyp_mode() on currently online CPUs >> using on_each_cpu(). If a CPU came online after this point and before calling >> register_cpu_notifier(), that CPU would remain uninitialized because this >> subsystem would miss the hot-online event. This patch fixes this bug and >> also uses the new synchronization method (instead of get/put_online_cpus()) >> to ensure that we don't deadlock with CPU hotplug. >> > > Yes, that was my conclusion as well. Thanks for clarifying. (It could > be noted in the commit message as well if you should feel so inclined). > Please find the patch with updated changelog (and your Ack) below. (No changes in code). From: Srivatsa S. Bhat Subject: [PATCH] arm, kvm: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); In the existing arm kvm code, there is no synchronization with CPU hotplug to avoid missing the hotplug events that might occur after invoking init_hyp_mode() and before calling register_cpu_notifier(). Fix this bug and also use the new synchronization method (instead of get/put_online_cpus()) to ensure that we don't deadlock with CPU hotplug. Cc: Gleb Natapov Cc: Russell King Cc: Ingo Molnar Acked-by: Paolo Bonzini Acked-by: Christoffer Dall Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki

ARM: KVM: fix warning in mmu.c

2014-03-03T01:15:25Z

Compiling with THP enabled leads to the following warning: arch/arm/kvm/mmu.c: In function ‘unmap_range’: arch/arm/kvm/mmu.c:177:39: warning: ‘pte’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (kvm_pmd_huge(*pmd) || page_empty(pte)) { ^ Code inspection reveals that these two cases are mutually exclusive, so GCC is a bit overzealous here. Silence it anyway by initializing pte to NULL and testing it later on. Signed-off-by: Marc Zyngier Acked-by: Christoffer Dall

ARM: KVM: trap VM system registers until MMU and caches are ON

2014-03-03T01:15:24Z

In order to be able to detect the point where the guest enables its MMU and caches, trap all the VM related system registers. Once we see the guest enabling both the MMU and the caches, we can go back to a saner mode of operation, which is to leave these registers in complete control of the guest. Signed-off-by: Marc Zyngier Acked-by: Catalin Marinas Reviewed-by: Christoffer Dall

ARM: KVM: add world-switch for AMAIR{0,1}

2014-03-03T01:15:24Z

HCR.TVM traps (among other things) accesses to AMAIR0 and AMAIR1. In order to minimise the amount of surprise a guest could generate by trying to access these registers with caches off, add them to the list of registers we switch/handle. Signed-off-by: Marc Zyngier Reviewed-by: Christoffer Dall Acked-by: Catalin Marinas

ARM: KVM: introduce per-vcpu HYP Configuration Register

2014-03-03T01:15:23Z

So far, KVM/ARM used a fixed HCR configuration per guest, except for the VI/VF/VA bits to control the interrupt in absence of VGIC. With the upcoming need to dynamically reconfigure trapping, it becomes necessary to allow the HCR to be changed on a per-vcpu basis. The fix here is to mimic what KVM/arm64 already does: a per vcpu HCR field, initialized at setup time. Signed-off-by: Marc Zyngier Reviewed-by: Christoffer Dall Acked-by: Catalin Marinas

ARM: KVM: fix ordering of 64bit coprocessor accesses

2014-03-03T01:15:23Z

Commit 240e99cbd00a (ARM: KVM: Fix 64-bit coprocessor handling) added an ordering dependency for the 64bit registers. The order described is: CRn, CRm, Op1, Op2, 64bit-first. Unfortunately, the implementation is: CRn, 64bit-first, CRm... Move the 64bit test to be last in order to match the documentation. Signed-off-by: Marc Zyngier Reviewed-by: Christoffer Dall Acked-by: Catalin Marinas

ARM: KVM: fix handling of trapped 64bit coprocessor accesses

2014-03-03T01:15:23Z

Commit 240e99cbd00a (ARM: KVM: Fix 64-bit coprocessor handling) changed the way we match the 64bit coprocessor access from user space, but didn't update the trap handler for the same set of registers. The effect is that a trapped 64bit access is never matched, leading to a fault being injected into the guest. This went unnoticed as we didn't really trap any 64bit register so far. Placing the CRm field of the access into the CRn field of the matching structure fixes the problem. Also update the debug feature to emit the expected string in case of failing match. Signed-off-by: Marc Zyngier Reviewed-by: Christoffer Dall Acked-by: Catalin Marinas