- 19 Apr, 2021 1 commit
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Sean Christopherson authored
Let the TDP MMU yield when unmapping a range in response to a MMU notification, if yielding is allowed by said notification. There is no reason to disallow yielding in this case, and in theory the range being invalidated could be quite large. Cc: Ben Gardon <bgardon@google.com> Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20210402005658.3024832-11-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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- 17 Apr, 2021 39 commits
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Sean Christopherson authored
Defer acquiring mmu_lock in the MMU notifier paths until a "hit" has been detected in the memslots, i.e. don't take the lock for notifications that don't affect the guest. For small VMs, spurious locking is a minor annoyance. And for "volatile" setups where the majority of notifications _are_ relevant, this barely qualifies as an optimization. But, for large VMs (hundreds of threads) with static setups, e.g. no page migration, no swapping, etc..., the vast majority of MMU notifier callbacks will be unrelated to the guest, e.g. will often be in response to the userspace VMM adjusting its own virtual address space. In such large VMs, acquiring mmu_lock can be painful as it blocks vCPUs from handling page faults. In some scenarios it can even be "fatal" in the sense that it causes unacceptable brownouts, e.g. when rebuilding huge pages after live migration, a significant percentage of vCPUs will be attempting to handle page faults. x86's TDP MMU implementation is especially susceptible to spurious locking due it taking mmu_lock for read when handling page faults. Because rwlock is fair, a single writer will stall future readers, while the writer is itself stalled waiting for in-progress readers to complete. This is exacerbated by the MMU notifiers often firing multiple times in quick succession, e.g. moving a page will (always?) invoke three separate notifiers: .invalidate_range_start(), invalidate_range_end(), and .change_pte(). Unnecessarily taking mmu_lock each time means even a single spurious sequence can be problematic. Note, this optimizes only the unpaired callbacks. Optimizing the .invalidate_range_{start,end}() pairs is more complex and will be done in a future patch. Suggested-by:Ben Gardon <bgardon@google.com> Signed-off-by:
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Sean Christopherson authored
Acquire and release mmu_lock in the __kvm_handle_hva_range() helper instead of requiring the caller to do the same. This paves the way for future patches to take mmu_lock if and only if an overlapping memslot is found, without also having to introduce the on_lock() shenanigans used to manipulate the notifier count and sequence. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Yank out the hva-based MMU notifier APIs now that all architectures that use the notifiers have moved to the gfn-based APIs. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Move PPC to the gfn-base MMU notifier APIs, and update all 15 bajillion PPC-internal hooks to work with gfns instead of hvas. No meaningful functional change intended, though the exact order of operations is slightly different since the memslot lookups occur before calling into arch code. Signed-off-by:
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Sean Christopherson authored
Move MIPS to the gfn-based MMU notifier APIs, which do the hva->gfn lookup in common code, and whose code is nearly identical to MIPS' lookup. No meaningful functional change intended, though the exact order of operations is slightly different since the memslot lookups occur before calling into arch code. Signed-off-by:
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Sean Christopherson authored
Move arm64 to the gfn-base MMU notifier APIs, which do the hva->gfn lookup in common code. No meaningful functional change intended, though the exact order of operations is slightly different since the memslot lookups occur before calling into arch code. Reviewed-by:
Marc Zyngier <maz@kernel.org> Tested-by:
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Sean Christopherson authored
Move the hva->gfn lookup for MMU notifiers into common code. Every arch does a similar lookup, and some arch code is all but identical across multiple architectures. In addition to consolidating code, this will allow introducing optimizations that will benefit all architectures without incurring multiple walks of the memslots, e.g. by taking mmu_lock if and only if a relevant range exists in the memslots. The use of __always_inline to avoid indirect call retpolines, as done by x86, may also benefit other architectures. Consolidating the lookups also fixes a wart in x86, where the legacy MMU and TDP MMU each do their own memslot walks. Lastly, future enhancements to the memslot implementation, e.g. to add an interval tree to track host address, will need to touch far less arch specific code. MIPS, PPC, and arm64 will be converted one at a time in future patches. Signed-off-by:
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Sean Christopherson authored
In KVM's .change_pte() notification callback, replace the notifier sequence bump with a WARN_ON assertion that the notifier count is elevated. An elevated count provides stricter protections than bumping the sequence, and the sequence is guarnateed to be bumped before the count hits zero. When .change_pte() was added by commit 828502d3 ("ksm: add mmu_notifier set_pte_at_notify()"), bumping the sequence was necessary as .change_pte() would be invoked without any surrounding notifications. However, since commit 6bdb913f ("mm: wrap calls to set_pte_at_notify with invalidate_range_start and invalidate_range_end"), all calls to .change_pte() are guaranteed to be surrounded by start() and end(), and so are guaranteed to run with an elevated notifier count. Note, wrapping .change_pte() with .invalidate_range_{start,end}() is a bug of sorts, as invalidating the secondary MMU's (KVM's) PTE defeats the purpose of .change_pte(). Every arch's kvm_set_spte_hva() assumes .change_pte() is called when the relevant SPTE is present in KVM's MMU, as the original goal was to accelerate Kernel Samepage Merging (KSM) by updating KVM's SPTEs without requiring a VM-Exit (due to invalidating the SPTE). I.e. it means that .change_pte() is effectively dead code on _all_ architectures. x86 and MIPS are clearcut nops if the old SPTE is not-present, and that is guaranteed due to the prior invalidation. PPC simply unmaps the SPTE, which again should be a nop due to the invalidation. arm64 is a bit murky, but it's also likely a nop because kvm_pgtable_stage2_map() is called without a cache pointer, which means it will map an entry if and only if an existing PTE was found. For now, take advantage of the bug to simplify future consolidation of KVMs's MMU notifier code. Doing so will not greatly complicate fixing .change_pte(), assuming it's even worth fixing. .change_pte() has been broken for 8+ years and no one has complained. Even if there are KSM+KVM users that care deeply about its performance, the benefits of avoiding VM-Exits via .change_pte() need to be reevaluated to justify the added complexity and testing burden. Ripping out .change_pte() entirely would be a lot easier. Signed-off-by:
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Paolo Bonzini authored
Return 1 from kvm_unmap_hva_range and kvm_set_spte_hva if a flush is needed, so that the generic code can coalesce the flushes. Signed-off-by: -
Paolo Bonzini authored
Since all calls to kvm_flush_remote_tlbs must be preceded by kvm_mips_callbacks->prepare_flush_shadow, repurpose kvm_arch_flush_remote_tlb to invoke it. This makes it possible to use the TLB flushing mechanism provided by the generic MMU notifier code. Signed-off-by: -
Paolo Bonzini authored
Both trap-and-emulate and VZ have a single implementation that covers both .flush_shadow_all and .flush_shadow_memslot, and both of them end with a call to kvm_flush_remote_tlbs. Unify the callbacks into one and extract the call to kvm_flush_remote_tlbs. The next patches will pull it further out of the the architecture-specific MMU notifier functions kvm_unmap_hva_range and kvm_set_spte_hva. Signed-off-by: -
Paolo Bonzini authored
memslots are stored in RCU and there should be no need to change them. Signed-off-by: -
Sean Christopherson authored
Use GFP_KERNEL_ACCOUNT when allocating vCPUs to make it more obvious that that the allocations are accounted, to make it easier to audit KVM's allocations in the future, and to be consistent with other cache usage in KVM. When using SLAB/SLUB, this is a nop as the cache itself is created with SLAB_ACCOUNT. When using SLOB, there are caveats within caveats. SLOB doesn't honor SLAB_ACCOUNT, so passing GFP_KERNEL_ACCOUNT will result in vCPU allocations now being accounted. But, even that depends on internal SLOB details as SLOB will only go to the page allocator when its cache is depleted. That just happens to be extremely likely for vCPUs because the size of kvm_vcpu is larger than the a page for almost all combinations of architecture and page size. Whether or not the SLOB behavior is by design is unknown; it's just as likely that no SLOB users care about accounding and so no one has bothered to implemented support in SLOB. Regardless, accounting vCPU allocations will not break SLOB+KVM+cgroup users, if any exist. Reviewed-by:
Wanpeng Li <kernellwp@gmail.com> Acked-by:
David Rientjes <rientjes@google.com> Signed-off-by:
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Paolo Bonzini authored
When using manual protection of dirty pages, it is not necessary to protect nested page tables down to the 4K level; instead KVM can protect only hugepages in order to split them lazily, and delay write protection at 4K-granularity until KVM_CLEAR_DIRTY_LOG. This was overlooked in the TDP MMU, so do it there as well. Fixes: a6a0b05d ("kvm: x86/mmu: Support dirty logging for the TDP MMU") Cc: Ben Gardon <bgardon@google.com> Reviewed-by:
Keqian Zhu <zhukeqian1@huawei.com> Signed-off-by:
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Maxim Levitsky authored
Define KVM_GUESTDBG_VALID_MASK and use it to implement this capabiity. Compile tested only. Signed-off-by:
Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210401135451.1004564-6-mlevitsk@redhat.com> Signed-off-by:
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Maxim Levitsky authored
Move KVM_GUESTDBG_VALID_MASK to kvm_host.h and use it to return the value of this capability. Compile tested only. Signed-off-by:
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Maxim Levitsky authored
Store the supported bits into KVM_GUESTDBG_VALID_MASK macro, similar to how arm does this. Signed-off-by:
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Paolo Bonzini authored
This capability will allow the user to know which KVM_GUESTDBG_* bits are supported. Signed-off-by:
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Maxim Levitsky authored
Injected interrupts/nmi should not block a pending exception, but rather be either lost if nested hypervisor doesn't intercept the pending exception (as in stock x86), or be delivered in exitintinfo/IDT_VECTORING_INFO field, as a part of a VMexit that corresponds to the pending exception. The only reason for an exception to be blocked is when nested run is pending (and that can't really happen currently but still worth checking for). Signed-off-by:
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Yang Yingliang authored
Signed-off-by:
Yang Yingliang <yangyingliang@huawei.com> Message-Id: <20210401142514.1688199-1-yangyingliang@huawei.com> Signed-off-by:
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Maxim Levitsky authored
While KVM's MMU should be fully reset by loading of nested CR0/CR3/CR4 by KVM_SET_SREGS, we are not in nested mode yet when we do it and therefore only root_mmu is reset. On regular nested entries we call nested_svm_load_cr3 which both updates the guest's CR3 in the MMU when it is needed, and it also initializes the mmu again which makes it initialize the walk_mmu as well when nested paging is enabled in both host and guest. Since we don't call nested_svm_load_cr3 on nested state load, the walk_mmu can be left uninitialized, which can lead to a NULL pointer dereference while accessing it if we happen to get a nested page fault right after entering the nested guest first time after the migration and we decide to emulate it, which leads to the emulator trying to access walk_mmu->gva_to_gpa which is NULL. Therefore we should call this function on nested state load as well. Suggested-by:
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David Edmondson authored
When dumping the current VMCS state, include the MSRs that are being automatically loaded/stored during VM entry/exit. Suggested-by:
David Edmondson <david.edmondson@oracle.com> Message-Id: <20210318120841.133123-6-david.edmondson@oracle.com> Signed-off-by:
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David Edmondson authored
If EFER is not being loaded from the VMCS, show the effective value by reference to the MSR autoload list or calculation. Suggested-by:
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David Edmondson authored
When deciding whether to dump the GUEST_IA32_EFER and GUEST_IA32_PAT fields of the VMCS, examine only the VM entry load controls, as saving on VM exit has no effect on whether VM entry succeeds or fails. Suggested-by:
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David Edmondson authored
Show EFER and PAT based on their individual entry/exit controls. Signed-off-by:
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David Edmondson authored
If the VM entry/exit controls for loading/saving MSR_EFER are either not available (an older processor or explicitly disabled) or not used (host and guest values are the same), reading GUEST_IA32_EFER from the VMCS returns an inaccurate value. Because of this, in dump_vmcs() don't use GUEST_IA32_EFER to decide whether to print the PDPTRs - always do so if the fields exist. Fixes: 4eb64dce ("KVM: x86: dump VMCS on invalid entry") Signed-off-by:
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Maxim Levitsky authored
Currently to support Intel->AMD migration, if CPU vendor is GenuineIntel, we emulate the full 64 value for MSR_IA32_SYSENTER_{EIP|ESP} msrs, and we also emulate the sysenter/sysexit instruction in long mode. (Emulator does still refuse to emulate sysenter in 64 bit mode, on the ground that the code for that wasn't tested and likely has no users) However when virtual vmload/vmsave is enabled, the vmload instruction will update these 32 bit msrs without triggering their msr intercept, which will lead to having stale values in kvm's shadow copy of these msrs, which relies on the intercept to be up to date. Fix/optimize this by doing the following: 1. Enable the MSR intercepts for SYSENTER MSRs iff vendor=GenuineIntel (This is both a tiny optimization and also ensures that in case the guest cpu vendor is AMD, the msrs will be 32 bit wide as AMD defined). 2. Store only high 32 bit part of these msrs on interception and combine it with hardware msr value on intercepted read/writes iff vendor=GenuineIntel. 3. Disable vmload/vmsave virtualization if vendor=GenuineIntel. (It is somewhat insane to set vendor=GenuineIntel and still enable SVM for the guest but well whatever). Then zero the high 32 bit parts when kvm intercepts and emulates vmload. Thanks a lot to Paulo Bonzini for helping me with fixing this in the most correct way. This patch fixes nested migration of 32 bit nested guests, that was broken because incorrect cached values of SYSENTER msrs were stored in the migration stream if L1 changed these msrs with vmload prior to L2 entry. Signed-off-by: -
Maxim Levitsky authored
This is similar to existing 'guest_cpuid_is_amd_or_hygon' Signed-off-by:
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Sean Christopherson authored
Switch to GFP_KERNEL_ACCOUNT for a handful of allocations that are clearly associated with a single task/VM. Note, there are a several SEV allocations that aren't accounted, but those can (hopefully) be fixed by using the local stack for memory. Signed-off-by:
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Sean Christopherson authored
Reject KVM_SEV_INIT and KVM_SEV_ES_INIT if they are attempted after one or more vCPUs have been created. KVM assumes a VM is tagged SEV/SEV-ES prior to vCPU creation, e.g. init_vmcb() needs to mark the VMCB as SEV enabled, and svm_create_vcpu() needs to allocate the VMSA. At best, creating vCPUs before SEV/SEV-ES init will lead to unexpected errors and/or behavior, and at worst it will crash the host, e.g. sev_launch_update_vmsa() will dereference a null svm->vmsa pointer. Fixes: 1654efcb ("KVM: SVM: Add KVM_SEV_INIT command") Fixes: ad73109a ("KVM: SVM: Provide support to launch and run an SEV-ES guest") Cc: stable@vger.kernel.org Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
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Sean Christopherson authored
Set sev->es_active only after the guts of KVM_SEV_ES_INIT succeeds. If the command fails, e.g. because SEV is already active or there are no available ASIDs, then es_active will be left set even though the VM is not fully SEV-ES capable. Refactor the code so that "es_active" is passed on the stack instead of being prematurely shoved into sev_info, both to avoid having to unwind sev_info and so that it's more obvious what actually consumes es_active in sev_guest_init() and its helpers. Fixes: ad73109a ("KVM: SVM: Provide support to launch and run an SEV-ES guest") Cc: stable@vger.kernel.org Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
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Sean Christopherson authored
Use the kvm_for_each_vcpu() helper to iterate over vCPUs when encrypting VMSAs for SEV, which effectively switches to use online_vcpus instead of created_vcpus. This fixes a possible null-pointer dereference as created_vcpus does not guarantee a vCPU exists, since it is updated at the very beginning of KVM_CREATE_VCPU. created_vcpus exists to allow the bulk of vCPU creation to run in parallel, while still correctly restricting the max number of max vCPUs. Fixes: ad73109a ("KVM: SVM: Provide support to launch and run an SEV-ES guest") Cc: stable@vger.kernel.org Cc: Brijesh Singh <brijesh.singh@amd.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
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Sean Christopherson authored
Use a basic NOT+AND sequence to clear the Accessed bit in TDP MMU SPTEs, as opposed to the fancy ffs()+clear_bit() logic that was copied from the legacy MMU. The legacy MMU uses clear_bit() because it is operating on the SPTE itself, i.e. clearing needs to be atomic. The TDP MMU operates on a local variable that it later writes to the SPTE, and so doesn't need to be atomic or even resident in memory. Opportunistically drop unnecessary initialization of new_spte, it's guaranteed to be written before being accessed. Using NOT+AND instead of ffs()+clear_bit() reduces the sequence from: 0x0000000000058be6 <+134>: test %rax,%rax 0x0000000000058be9 <+137>: je 0x58bf4 <age_gfn_range+148> 0x0000000000058beb <+139>: test %rax,%rdi 0x0000000000058bee <+142>: je 0x58cdc <age_gfn_range+380> 0x0000000000058bf4 <+148>: mov %rdi,0x8(%rsp) 0x0000000000058bf9 <+153>: mov $0xffffffff,%edx 0x0000000000058bfe <+158>: bsf %eax,%edx 0x0000000000058c01 <+161>: movslq %edx,%rdx 0x0000000000058c04 <+164>: lock btr %rdx,0x8(%rsp) 0x0000000000058c0b <+171>: mov 0x8(%rsp),%r15 to: 0x0000000000058bdd <+125>: test %rax,%rax 0x0000000000058be0 <+128>: je 0x58beb <age_gfn_range+139> 0x0000000000058be2 <+130>: test %rax,%r8 0x0000000000058be5 <+133>: je 0x58cc0 <age_gfn_range+352> 0x0000000000058beb <+139>: not %rax 0x0000000000058bee <+142>: and %r8,%rax 0x0000000000058bf1 <+145>: mov %rax,%r15 thus eliminating several memory accesses, including a locked access. Cc: Ben Gardon <bgardon@google.com> Signed-off-by:
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Sean Christopherson authored
Don't clear the dirty bit when aging a TDP MMU SPTE (in response to a MMU notifier event). Prematurely clearing the dirty bit could cause spurious PML updates if aging a page happened to coincide with dirty logging. Note, tdp_mmu_set_spte_no_acc_track() flows into __handle_changed_spte(), so the host PFN will be marked dirty, i.e. there is no potential for data corruption. Fixes: a6a0b05d ("kvm: x86/mmu: Support dirty logging for the TDP MMU") Cc: Ben Gardon <bgardon@google.com> Signed-off-by:
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Sean Christopherson authored
Remove x86's trace_kvm_age_page() tracepoint. It's mostly redundant with the common trace_kvm_age_hva() tracepoint, and if there is a need for the extra details, e.g. gfn, referenced, etc... those details should be added to the common tracepoint so that all architectures and MMUs benefit from the info. Signed-off-by:
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Sean Christopherson authored
Move arm64's MMU notifier trace events into common code in preparation for doing the hva->gfn lookup in common code. The alternative would be to trace the gfn instead of hva, but that's not obviously better and could also be done in common code. Tracing the notifiers is also quite handy for debug regardless of architecture. Remove a completely redundant tracepoint from PPC e500. Signed-off-by:
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Sean Christopherson authored
Move the prototypes for the MMU notifier callbacks out of arch code and into common code. There is no benefit to having each arch replicate the prototypes since any deviation from the invocation in common code will explode. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Use the leaf-only TDP iterator when changing the SPTE in reaction to a MMU notifier. Practically speaking, this is a nop since the guts of the loop explicitly looks for 4k SPTEs, which are always leaf SPTEs. Switch the iterator to match age_gfn_range() and test_age_gfn() so that a future patch can consolidate the core iterating logic. No real functional change intended. Signed-off-by:
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Sean Christopherson authored
Move the address space ID check that is performed when iterating over roots into the macro helpers to consolidate code. No functional change intended. Signed-off-by:
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