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2014-09-22KVM: PPC: Book3S HV: Only accept host PVR value for guest PVRPaul Mackerras
Since the guest can read the machine's PVR (Processor Version Register) directly and see the real value, we should disallow userspace from setting any value for the guest's PVR other than the real host value. Therefore this makes kvm_arch_vcpu_set_sregs_hv() check the supplied PVR value and return an error if it is different from the host value, which has been put into vcpu->arch.pvr at vcpu creation time. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Book3S HV: Increase timeout for grabbing secondary threadsPaul Mackerras
Occasional failures have been seen with split-core mode and migration where the message "KVM: couldn't grab cpu" appears. This increases the length of time that we wait from 1ms to 10ms, which seems to work around the issue. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Remove shared defines for SPE and AltiVec interruptsMihai Caraman
We currently decide at compile-time which of the SPE or AltiVec units to support exclusively. Guard kernel defines with CONFIG_SPE_POSSIBLE and CONFIG_PPC_E500MC and remove shared defines. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Remove the tasklet used by the hrtimerMihai Caraman
Powerpc timer implementation is a copycat version of s390. Now that they removed the tasklet with commit ea74c0ea1b24a6978a6ebc80ba4dbc7b7848b32d follow this optimization. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: Emulate debug registers and exceptionBharat Bhushan
This patch emulates debug registers and debug exception to support guest using debug resource. This enables running gdb/kgdb etc in guest. On BOOKE architecture we cannot share debug resources between QEMU and guest because: When QEMU is using debug resources then debug exception must be always enabled. To achieve this we set MSR_DE and also set MSRP_DEP so guest cannot change MSR_DE. When emulating debug resource for guest we want guest to control MSR_DE (enable/disable debug interrupt on need). So above mentioned two configuration cannot be supported at the same time. So the result is that we cannot share debug resources between QEMU and Guest on BOOKE architecture. In the current design QEMU gets priority over guest, this means that if QEMU is using debug resources then guest cannot use them and if guest is using debug resource then QEMU can overwrite them. Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Move ONE_REG AltiVec support to powerpcMihai Caraman
Move ONE_REG AltiVec support to powerpc generic layer. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Make ONE_REG powerpc genericMihai Caraman
Make ONE_REG generic for server and embedded architectures by moving kvm_vcpu_ioctl_get_one_reg() and kvm_vcpu_ioctl_set_one_reg() functions to powerpc layer. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Book3e: Add AltiVec supportMihai Caraman
Add AltiVec support in KVM for Book3e. FPU support gracefully reuse host infrastructure so follow the same approach for AltiVec. Book3e specification defines shared interrupt numbers for SPE and AltiVec units. Still SPE is present in e200/e500v2 cores while AltiVec is present in e6500 core. So we can currently decide at compile-time which of the SPE or AltiVec units to support exclusively by using CONFIG_SPE_POSSIBLE and CONFIG_PPC_E500MC defines. As Alexander Graf suggested, keep SPE and AltiVec exception handlers distinct to improve code readability. Guests have the privilege to enable AltiVec, so we always need to support AltiVec in KVM and implicitly in host to reflect interrupts and to save/restore the unit context. KVM will be loaded on cores with AltiVec unit only if CONFIG_ALTIVEC is defined. Use this define to guard KVM AltiVec logic. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Book3E: Increase FPU lazinessMihai Caraman
Increase FPU laziness by loading the guest state into the unit before entering the guest instead of doing it on each vcpu schedule. Without this improvement an interrupt may claim floating point corrupting guest state. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: Add one_reg documentation of SPRG9 and DBSRBharat Bhushan
This was missed in respective one_reg implementation patch. Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: Book3S HV: Add register name when loading tocMichael Neuling
Add 'r' to register name r2 in kvmppc_hv_enter. Also update comment at the top of kvmppc_hv_enter to indicate that R2/TOC is non-volatile. Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22powerpc/booke: Revert SPE/AltiVec common defines for interrupt numbersMihai Caraman
Book3E specification defines shared interrupt numbers for SPE and AltiVec units. Still SPE is present in e200/e500v2 cores while AltiVec is present in e6500 core. So we can currently decide at compile-time which unit to support exclusively. As Alexander Graf suggested, this will improve code readability especially in KVM. Use distinct defines to identify SPE/AltiVec interrupt numbers, reverting c58ce397 and 6b310fc5 patches that added common defines. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Acked-by: Scott Wood <scottwood@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22powerpc/booke: Restrict SPE exception handlers to e200/e500 coresMihai Caraman
SPE exception handlers are now defined for 32-bit e500mc cores even though SPE unit is not present and CONFIG_SPE is undefined. Restrict SPE exception handlers to e200/e500 cores adding CONFIG_SPE_POSSIBLE and consequently guard __stup_ivors and __setup_cpu functions. Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com> Acked-by: Scott Wood <scottwood@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: Add one reg interface for DBSRBharat Bhushan
Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: Guest and hardware visible debug registers are sameBharat Bhushan
Guest visible debug register and hardware visible debug registers are same, so ther is no need to have arch->shadow_dbg_reg, instead use arch->dbg_reg. Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: Clear guest dbsr in userspace exit KVM_EXIT_DEBUGBharat Bhushan
Dbsr is not visible to userspace and we do not think any need to expose this to userspace because: Userspace cannot inject debug interrupt to guest (as this does not know guest ability to handle debug interrupt), so userspace will always clear DBSR. Now if userspace has to always clear DBSR in KVM_EXIT_DEBUG handling then clearing dbsr in kernel looks simple as this avoid doing SET_SREGS/set_one_reg() to clear DBSR Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: Allow guest to change MSR_DEBharat Bhushan
This patch changes the default behavior of MSRP_DEP, that is guest is not allowed to change the MSR_DE, to guest can change MSR_DE. When userspace is debugging guest then it override the default behavior and set MSRP_DEP. This stops guest to change MSR_DE when userspace is debugging guest. Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE : Emulate rfdi instructionBharat Bhushan
This patch adds "rfdi" instruction emulation which is required for guest debug hander on BOOKE-HV Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-22KVM: PPC: BOOKE: allow debug interrupt at "debug level"Bharat Bhushan
Debug interrupt can be either "critical level" or "debug level". There are separate set of save/restore registers used for different level. Example: DSRR0/DSRR1 are used for "debug level" and CSRR0/CSRR1 are used for critical level debug interrupt. Using CPU_FTR_DEBUG_LVL_EXC to decide which interrupt level to be used. Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
2014-09-17kvm: Make init_rmode_identity_map() return 0 on success.Tang Chen
In init_rmode_identity_map(), there two variables indicating the return value, r and ret, and it return 0 on error, 1 on success. The function is only called by vmx_create_vcpu(), and ret is redundant. This patch removes the redundant variable, and makes init_rmode_identity_map() return 0 on success, -errno on failure. Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-17kvm: Remove ept_identity_pagetable from struct kvm_arch.Tang Chen
kvm_arch->ept_identity_pagetable holds the ept identity pagetable page. But it is never used to refer to the page at all. In vcpu initialization, it indicates two things: 1. indicates if ept page is allocated 2. indicates if a memory slot for identity page is initialized Actually, kvm_arch->ept_identity_pagetable_done is enough to tell if the ept identity pagetable is initialized. So we can remove ept_identity_pagetable. NOTE: In the original code, ept identity pagetable page is pinned in memroy. As a result, it cannot be migrated/hot-removed. After this patch, since kvm_arch->ept_identity_pagetable is removed, ept identity pagetable page is no longer pinned in memory. And it can be migrated/hot-removed. Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com> Reviewed-by: Gleb Natapov <gleb@kernel.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-17KVM: VFIO: register kvm_device_ops dynamicallyWill Deacon
Now that we have a dynamic means to register kvm_device_ops, use that for the VFIO kvm device, instead of relying on the static table. This is achieved by a module_init call to register the ops with KVM. Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Alex Williamson <Alex.Williamson@redhat.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-17KVM: s390: register flic ops dynamicallyCornelia Huck
Using the new kvm_register_device_ops() interface makes us get rid of an #ifdef in common code. Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-17KVM: ARM: vgic: register kvm_device_ops dynamicallyWill Deacon
Now that we have a dynamic means to register kvm_device_ops, use that for the ARM VGIC, instead of relying on the static table. Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-17KVM: device: add simple registration mechanism for kvm_device_opsWill Deacon
kvm_ioctl_create_device currently has knowledge of all the device types and their associated ops. This is fairly inflexible when adding support for new in-kernel device emulations, so move what we currently have out into a table, which can support dynamic registration of ops by new drivers for virtual hardware. Cc: Alex Williamson <Alex.Williamson@redhat.com> Cc: Alex Graf <agraf@suse.de> Cc: Gleb Natapov <gleb@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-16kvm: ioapic: conditionally delay irq delivery duringeoi broadcastZhang Haoyu
Currently, we call ioapic_service() immediately when we find the irq is still active during eoi broadcast. But for real hardware, there's some delay between the EOI writing and irq delivery. If we do not emulate this behavior, and re-inject the interrupt immediately after the guest sends an EOI and re-enables interrupts, a guest might spend all its time in the ISR if it has a broken handler for a level-triggered interrupt. Such livelock actually happens with Windows guests when resuming from hibernation. As there's no way to recognize the broken handle from new raised ones, this patch delays an interrupt if 10.000 consecutive EOIs found that the interrupt was still high. The guest can then make a little forward progress, until a proper IRQ handler is set or until some detection routine in the guest (such as Linux's note_interrupt()) recognizes the situation. Cc: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Zhang Haoyu <zhanghy@sangfor.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-16KVM: x86: Use kvm_make_request when applicableGuo Hui Liu
This patch replace the set_bit method by kvm_make_request to make code more readable and consistent. Signed-off-by: Guo Hui Liu <liuguohui@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-11KVM: x86: make apic_accept_irq tracepoint more genericPaolo Bonzini
Initially the tracepoint was added only to the APIC_DM_FIXED case, also because it reported coalesced interrupts that only made sense for that case. However, the coalesced argument is not used anymore and tracing other delivery modes is useful, so hoist the call out of the switch statement. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-11kvm: Use APIC_DEFAULT_PHYS_BASE macro as the apic access page address.Tang Chen
We have APIC_DEFAULT_PHYS_BASE defined as 0xfee00000, which is also the address of apic access page. So use this macro. Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com> Reviewed-by: Gleb Natapov <gleb@kernel.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-11Merge tag 'kvm-s390-next-20140910' of ↵Paolo Bonzini
git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into kvm-next KVM: s390: Fixes and features for next (3.18) 1. Crypto/CPACF support: To enable the MSA4 instructions we have to provide a common control structure for each SIE control block 2. Two cleanups found by a static code checker: one redundant assignment and one useless if 3. Fix the page handling of the diag10 ballooning interface. If the guest freed the pages at absolute 0 some checks and frees were incorrect 4. Limit guests to 16TB 5. Add __must_check to interrupt injection code
2014-09-10KVM: s390/interrupt: remove double assignmentChristian Borntraeger
r is already initialized to 0. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
2014-09-10KVM: s390/cmm: Fix prefix handling for diag 10 balloonChristian Borntraeger
The old handling of prefix pages was broken in the diag10 ballooner. We now rely on gmap_discard to check for start > end and do a slow path if the prefix swap pages are affected: 1. discard the pages from start to prefix 2. discard the absolute 0 pages 3. discard the pages after prefix swap to end Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
2014-09-10KVM: s390: get rid of constant condition in ipte_unlock_simpleChristian Borntraeger
Due to the earlier check we know that ipte_lock_count must be 0. No need to add a useless if. Let's make clear that we are going to always wakeup when we execute that code. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
2014-09-10KVM: s390: unintended fallthrough for external callChristian Borntraeger
We must not fallthrough if the conditions for external call are not met. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com> Cc: stable@vger.kernel.org
2014-09-10KVM: s390: Limit guest size to 16TBChristian Borntraeger
Currently we fill up a full 5 level page table to hold the guest mapping. Since commit "support gmap page tables with less than 5 levels" we can do better. Having more than 4 TB might be useful for some testing scenarios, so let's just limit ourselves to 16TB guest size. Having more than that is totally untested as I do not have enough swap space/memory. We continue to allow ucontrol the full size. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
2014-09-10KVM: s390: add __must_check to interrupt deliver functionsChristian Borntraeger
We now propagate interrupt injection errors back to the ioctl. We should mark functions that might fail with __must_check. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
2014-09-10KVM: CPACF: Enable MSA4 instructions for kvm guestTony Krowiak
We have to provide a per guest crypto block for the CPUs to enable MSA4 instructions. According to icainfo on z196 or later this enables CCM-AES-128, CMAC-AES-128, CMAC-AES-192 and CMAC-AES-256. Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com> Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> Reviewed-by: Michael Mueller <mimu@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> [split MSA4/protected key into two patches]
2014-09-10KVM: fix api documentation of KVM_GET_EMULATED_CPUIDAlex Bennée
It looks like when this was initially merged it got accidentally included in the following section. I've just moved it back in the correct section and re-numbered it as other ioctls have been added since. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Acked-by: Borislav Petkov <bp@suse.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-10KVM: document KVM_SET_GUEST_DEBUG apiAlex Bennée
In preparation for working on the ARM implementation I noticed the debug interface was missing from the API document. I've pieced together the expected behaviour from the code and commit messages written it up as best I can. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-05KVM: remove redundant assignments in __kvm_set_memory_regionChristian Borntraeger
__kvm_set_memory_region sets r to EINVAL very early. Doing it again is not necessary. The same is true later on, where r is assigned -ENOMEM twice. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-05KVM: remove redundant assigment of return value in kvm_dev_ioctlChristian Borntraeger
The first statement of kvm_dev_ioctl is long r = -EINVAL; No need to reassign the same value. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-05KVM: remove redundant check of in_spin_loopChristian Borntraeger
The expression `vcpu->spin_loop.in_spin_loop' is always true, because it is evaluated only when the condition `!vcpu->spin_loop.in_spin_loop' is false. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-05KVM: x86: propagate exception from permission checks on the nested page faultPaolo Bonzini
Currently, if a permission error happens during the translation of the final GPA to HPA, walk_addr_generic returns 0 but does not fill in walker->fault. To avoid this, add an x86_exception* argument to the translate_gpa function, and let it fill in walker->fault. The nested_page_fault field will be true, since the walk_mmu is the nested_mmu and translate_gpu instead operates on the "outer" (NPT) instance. Reported-by: Valentine Sinitsyn <valentine.sinitsyn@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-05KVM: x86: skip writeback on injection of nested exceptionPaolo Bonzini
If a nested page fault happens during emulation, we will inject a vmexit, not a page fault. However because writeback happens after the injection, we will write ctxt->eip from L2 into the L1 EIP. We do not write back if an instruction caused an interception vmexit---do the same for page faults. Suggested-by: Gleb Natapov <gleb@kernel.org> Reviewed-by: Gleb Natapov <gleb@kernel.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-03KVM: nSVM: propagate the NPF EXITINFO to the guestPaolo Bonzini
This is similar to what the EPT code does with the exit qualification. This allows the guest to see a valid value for bits 33:32. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-03KVM: x86: reserve bit 8 of non-leaf PDPEs and PML4Es in 64-bit mode on AMDPaolo Bonzini
Bit 8 would be the "global" bit, which does not quite make sense for non-leaf page table entries. Intel ignores it; AMD ignores it in PDEs, but reserves it in PDPEs and PML4Es. The SVM test is relying on this behavior, so enforce it. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-03KVM: mmio: cleanup kvm_set_mmio_spte_maskTiejun Chen
Just reuse rsvd_bits() inside kvm_set_mmio_spte_mask() for slightly better code. Signed-off-by: Tiejun Chen <tiejun.chen@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-03kvm: x86: fix stale mmio cache bugDavid Matlack
The following events can lead to an incorrect KVM_EXIT_MMIO bubbling up to userspace: (1) Guest accesses gpa X without a memory slot. The gfn is cached in struct kvm_vcpu_arch (mmio_gfn). On Intel EPT-enabled hosts, KVM sets the SPTE write-execute-noread so that future accesses cause EPT_MISCONFIGs. (2) Host userspace creates a memory slot via KVM_SET_USER_MEMORY_REGION covering the page just accessed. (3) Guest attempts to read or write to gpa X again. On Intel, this generates an EPT_MISCONFIG. The memory slot generation number that was incremented in (2) would normally take care of this but we fast path mmio faults through quickly_check_mmio_pf(), which only checks the per-vcpu mmio cache. Since we hit the cache, KVM passes a KVM_EXIT_MMIO up to userspace. This patch fixes the issue by using the memslot generation number to validate the mmio cache. Cc: stable@vger.kernel.org Signed-off-by: David Matlack <dmatlack@google.com> [xiaoguangrong: adjust the code to make it simpler for stable-tree fix.] Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Reviewed-by: David Matlack <dmatlack@google.com> Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Tested-by: David Matlack <dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-03kvm: fix potentially corrupt mmio cacheDavid Matlack
vcpu exits and memslot mutations can run concurrently as long as the vcpu does not aquire the slots mutex. Thus it is theoretically possible for memslots to change underneath a vcpu that is handling an exit. If we increment the memslot generation number again after synchronize_srcu_expedited(), vcpus can safely cache memslot generation without maintaining a single rcu_dereference through an entire vm exit. And much of the x86/kvm code does not maintain a single rcu_dereference of the current memslots during each exit. We can prevent the following case: vcpu (CPU 0) | thread (CPU 1) --------------------------------------------+-------------------------- 1 vm exit | 2 srcu_read_unlock(&kvm->srcu) | 3 decide to cache something based on | old memslots | 4 | change memslots | (increments generation) 5 | synchronize_srcu(&kvm->srcu); 6 retrieve generation # from new memslots | 7 tag cache with new memslot generation | 8 srcu_read_unlock(&kvm->srcu) | ... | <action based on cache occurs even | though the caching decision was based | on the old memslots> | ... | <action *continues* to occur until next | memslot generation change, which may | be never> | | By incrementing the generation after synchronizing with kvm->srcu readers, we ensure that the generation retrieved in (6) will become invalid soon after (8). Keeping the existing increment is not strictly necessary, but we do keep it and just move it for consistency from update_memslots to install_new_memslots. It invalidates old cached MMIOs immediately, instead of having to wait for the end of synchronize_srcu_expedited, which makes the code more clearly correct in case CPU 1 is preempted right after synchronize_srcu() returns. To avoid halving the generation space in SPTEs, always presume that the low bit of the generation is zero when reconstructing a generation number out of an SPTE. This effectively disables MMIO caching in SPTEs during the call to synchronize_srcu_expedited. Using the low bit this way is somewhat like a seqcount---where the protected thing is a cache, and instead of retrying we can simply punt if we observe the low bit to be 1. Cc: stable@vger.kernel.org Signed-off-by: David Matlack <dmatlack@google.com> Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Reviewed-by: David Matlack <dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-03KVM: do not bias the generation number in kvm_current_mmio_generationPaolo Bonzini
The next patch will give a meaning (a la seqcount) to the low bit of the generation number. Ensure that it matches between kvm->memslots->generation and kvm_current_mmio_generation(). Cc: stable@vger.kernel.org Reviewed-by: David Matlack <dmatlack@google.com> Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>