- 18 Nov, 2022 1 commit
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Paolo Bonzini authored
Since gfn_to_memslot() is relatively expensive, it helps to skip it if it the memslot cannot possibly have dirty logging enabled. In order to do this, add to struct kvm a counter of the number of log-page memslots. While the correct value can only be read with slots_lock taken, the NX recovery thread is content with using an approximate value. Therefore, the counter is an atomic_t. Based on https://lore.kernel.org/kvm/20221027200316.2221027-2-dmatlack@google.com/ by David Matlack. Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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- 17 Nov, 2022 39 commits
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Paolo Bonzini authored
This fixes three issues in nested SVM: 1) in the shutdown_interception() vmexit handler we call kvm_vcpu_reset(). However, if running nested and L1 doesn't intercept shutdown, the function resets vcpu->arch.hflags without properly leaving the nested state. This leaves the vCPU in inconsistent state and later triggers a kernel panic in SVM code. The same bug can likely be triggered by sending INIT via local apic to a vCPU which runs a nested guest. On VMX we are lucky that the issue can't happen because VMX always intercepts triple faults, thus triple fault in L2 will always be redirected to L1. Plus, handle_triple_fault() doesn't reset the vCPU. INIT IPI can't happen on VMX either because INIT events are masked while in VMX mode. Secondarily, KVM doesn't honour SHUTDOWN intercept bit of L1 on SVM. A normal hypervisor should always intercept SHUTDOWN, a unit test on the other hand might want to not do so. Finally, the guest can trigger a kernel non rate limited printk on SVM from the guest, which is fixed as well. Signed-off-by: -
Maxim Levitsky authored
It is valid to receive external interrupt and have broken IDT entry, which will lead to #GP with exit_int_into that will contain the index of the IDT entry (e.g any value). Other exceptions can happen as well, like #NP or #SS (if stack switch fails). Thus this warning can be user triggred and has very little value. Cc: stable@vger.kernel.org Signed-off-by:
Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20221103141351.50662-10-mlevitsk@redhat.com> Signed-off-by:
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Maxim Levitsky authored
Add a SVM implementation to triple_fault_test to test that emulated/injected shutdown works. Since instead of the VMX, the SVM allows the hypervisor to avoid intercepting shutdown in guest, don't intercept shutdown to test that KVM suports this correctly. Signed-off-by:
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Maxim Levitsky authored
This is SVM correctness fix - although a sane L1 would intercept SHUTDOWN event, it doesn't have to, so we have to honour this. Signed-off-by:
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Maxim Levitsky authored
Add test that tests that on SVM if L1 doesn't intercept SHUTDOWN, then L2 crashes L1 and doesn't crash L2 Signed-off-by:
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Maxim Levitsky authored
struct idt_entry will be used for a test which will break IDT on purpose. Signed-off-by:
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Maxim Levitsky authored
While not obivous, kvm_vcpu_reset() leaves the nested mode by clearing 'vcpu->arch.hflags' but it does so without all the required housekeeping. On SVM, it is possible to have a vCPU reset while in guest mode because unlike VMX, on SVM, INIT's are not latched in SVM non root mode and in addition to that L1 doesn't have to intercept triple fault, which should also trigger L1's reset if happens in L2 while L1 didn't intercept it. If one of the above conditions happen, KVM will continue to use vmcb02 while not having in the guest mode. Later the IA32_EFER will be cleared which will lead to freeing of the nested guest state which will (correctly) free the vmcb02, but since KVM still uses it (incorrectly) this will lead to a use after free and kernel crash. This issue is assigned CVE-2022-3344 Cc: stable@vger.kernel.org Signed-off-by:
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Maxim Levitsky authored
add kvm_leave_nested which wraps a call to nested_ops->leave_nested into a function. Cc: stable@vger.kernel.org Signed-off-by:
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Maxim Levitsky authored
Make sure that KVM uses vmcb01 before freeing nested state, and warn if that is not the case. This is a minimal fix for CVE-2022-3344 making the kernel print a warning instead of a kernel panic. Cc: stable@vger.kernel.org Signed-off-by:
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Maxim Levitsky authored
If the VM was terminated while nested, we free the nested state while the vCPU still is in nested mode. Soon a warning will be added for this condition. Cc: stable@vger.kernel.org Signed-off-by:
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David Matlack authored
Do not recover (i.e. zap) an NX Huge Page that is being dirty tracked, as it will just be faulted back in at the same 4KiB granularity when accessed by a vCPU. This may need to be changed if KVM ever supports 2MiB (or larger) dirty tracking granularity, or faulting huge pages during dirty tracking for reads/executes. However for now, these zaps are entirely wasteful. In order to check if this commit increases the CPU usage of the NX recovery worker thread I used a modified version of execute_perf_test [1] that supports splitting guest memory into multiple slots and reports /proc/pid/schedstat:se.sum_exec_runtime for the NX recovery worker just before tearing down the VM. The goal was to force a large number of NX Huge Page recoveries and see if the recovery worker used any more CPU. Test Setup: echo 1000 > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms echo 10 > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio Test Command: ./execute_perf_test -v64 -s anonymous_hugetlb_1gb -x 16 -o | kvm-nx-lpage-re:se.sum_exec_runtime | | ---------------------------------------- | Run | Before | After | ------- | ------------------ | ------------------- | 1 | 730.084105 | 724.375314 | 2 | 728.751339 | 740.581988 | 3 | 736.264720 | 757.078163 | Comparing the median results, this commit results in about a 1% increase CPU usage of the NX recovery worker when testing a VM with 16 slots. However, the effect is negligible with the default halving time of NX pages, which is 1 hour rather than 10 seconds given by period_ms = 1000, ratio = 10. [1] https://lore.kernel.org/kvm/20221019234050.3919566-2-dmatlack@google.com/Signed-off-by:David Matlack <dmatlack@google.com> Message-Id: <20221103204421.1146958-1-dmatlack@google.com> Signed-off-by:
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Paolo Bonzini authored
A removed SPTE is never present, hence the "if" in kvm_tdp_mmu_map only fails in the exact same conditions that the earlier loop tested in order to issue a "break". So, instead of checking twice the condition (upper level SPTEs could not be created or was frozen), just exit the loop with a goto---the usual poor-man C replacement for RAII early returns. While at it, do not use the "ret" variable for return values of functions that do not return a RET_PF_* enum. This is clearer and also makes it possible to initialize ret to RET_PF_RETRY. Suggested-by:
Robert Hoo <robert.hu@linux.intel.com> Signed-off-by:
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David Matlack authored
Now that the TDP MMU has a mechanism to split huge pages, use it in the fault path when a huge page needs to be replaced with a mapping at a lower level. This change reduces the negative performance impact of NX HugePages. Prior to this change if a vCPU executed from a huge page and NX HugePages was enabled, the vCPU would take a fault, zap the huge page, and mapping the faulting address at 4KiB with execute permissions enabled. The rest of the memory would be left *unmapped* and have to be faulted back in by the guest upon access (read, write, or execute). If guest is backed by 1GiB, a single execute instruction can zap an entire GiB of its physical address space. For example, it can take a VM longer to execute from its memory than to populate that memory in the first place: $ ./execute_perf_test -s anonymous_hugetlb_1gb -v96 Populating memory : 2.748378795s Executing from memory : 2.899670885s With this change, such faults split the huge page instead of zapping it, which avoids the non-present faults on the rest of the huge page: $ ./execute_perf_test -s anonymous_hugetlb_1gb -v96 Populating memory : 2.729544474s Executing from memory : 0.111965688s <--- This change also reduces the performance impact of dirty logging when eager_page_split=N. eager_page_split=N (abbreviated "eps=N" below) can be desirable for read-heavy workloads, as it avoids allocating memory to split huge pages that are never written and avoids increasing the TLB miss cost on reads of those pages. | Config: ept=Y, tdp_mmu=Y, 5% writes | | Iteration 1 dirty memory time | | --------------------------------------------- | vCPU Count | eps=N (Before) | eps=N (After) | eps=Y | ------------ | -------------- | ------------- | ------------ | 2 | 0.332305091s | 0.019615027s | 0.006108211s | 4 | 0.353096020s | 0.019452131s | 0.006214670s | 8 | 0.453938562s | 0.019748246s | 0.006610997s | 16 | 0.719095024s | 0.019972171s | 0.007757889s | 32 | 1.698727124s | 0.021361615s | 0.012274432s | 64 | 2.630673582s | 0.031122014s | 0.016994683s | 96 | 3.016535213s | 0.062608739s | 0.044760838s | Eager page splitting remains beneficial for write-heavy workloads, but the gap is now reduced. | Config: ept=Y, tdp_mmu=Y, 100% writes | | Iteration 1 dirty memory time | | --------------------------------------------- | vCPU Count | eps=N (Before) | eps=N (After) | eps=Y | ------------ | -------------- | ------------- | ------------ | 2 | 0.317710329s | 0.296204596s | 0.058689782s | 4 | 0.337102375s | 0.299841017s | 0.060343076s | 8 | 0.386025681s | 0.297274460s | 0.060399702s | 16 | 0.791462524s | 0.298942578s | 0.062508699s | 32 | 1.719646014s | 0.313101996s | 0.075984855s | 64 | 2.527973150s | 0.455779206s | 0.079789363s | 96 | 2.681123208s | 0.673778787s | 0.165386739s | Further study is needed to determine if the remaining gap is acceptable for customer workloads or if eager_page_split=N still requires a-priori knowledge of the VM workload, especially when considering these costs extrapolated out to large VMs with e.g. 416 vCPUs and 12TB RAM. Signed-off-by:Mingwei Zhang <mizhang@google.com> Message-Id: <20221109185905.486172-3-dmatlack@google.com> Signed-off-by:
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https://github.com/kvm-x86/linuxPaolo Bonzini authored
KVM selftests updates for 6.2 perf_util: - Add support for pinning vCPUs in dirty_log_perf_test. - Add a lightweight psuedo RNG for guest use, and use it to randomize the access pattern and write vs. read percentage in the so called "perf util" tests. - Rename the so called "perf_util" framework to "memstress". ucall: - Add a common pool-based ucall implementation (code dedup and pre-work for running SEV (and beyond) guests in selftests. - Fix an issue in ARM's single-step test when using the new pool-based implementation; LDREX/STREX don't play nice with single-step exceptions. init: - Provide a common constructor and arch hook, which will eventually be used by x86 to automatically select the right hypercall (AMD vs. Intel). x86: - Clean up x86's page tabe management. - Clean up and enhance the "smaller maxphyaddr" test, and add a related test to cover generic emulation failure. - Clean up the nEPT support checks. - Add X86_PROPERTY_* framework to retrieve multi-bit CPUID values.
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David Matlack authored
When checking for nEPT support in KVM, use kvm_get_feature_msr() instead of vcpu_get_msr() to retrieve KVM's default TRUE_PROCBASED_CTLS and PROCBASED_CTLS2 MSR values, i.e. don't require a VM+vCPU to query nEPT support. Suggested-by:
Sean Christopherson <seanjc@google.com> Signed-off-by:
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David Matlack authored
Now that a VM isn't needed to check for nEPT support, assert that KVM supports nEPT in prepare_eptp() instead of skipping the test, and push the TEST_REQUIRE() check out to individual tests. The require+assert are somewhat redundant and will incur some amount of ongoing maintenance burden, but placing the "require" logic in the test makes it easier to find/understand a test's requirements and in this case, provides a very strong hint that the test cares about nEPT. Suggested-by:
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Sean Christopherson authored
Drop kvm_get_supported_cpuid_entry() and its inner helper now that all known usage can use X86_FEATURE_*, X86_PROPERTY_*, X86_PMU_FEATURE_*, or the dedicated Family/Model helpers. Providing "raw" access to CPUID leafs is undesirable as it encourages open coding CPUID checks, which is often error prone and not self-documenting. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add KVM variants of the x86 Family and Model helpers, and use them in the PMU event filter test. Open code the retrieval of KVM's supported CPUID entry 0x1.0 in anticipation of dropping kvm_get_supported_cpuid_entry(). No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add dedicated helpers for getting x86's Family and Model, which are the last holdouts that "need" raw access to CPUID information. FMS info is a mess and requires not only splicing together multiple values, but requires doing so conditional in the Family case. Provide wrappers to reduce the odds of copy+paste errors, but mostly to allow for the eventual removal of kvm_get_supported_cpuid_entry(). No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add an X86_PMU_FEATURE_* framework to simplify probing architectural events on Intel PMUs, which require checking the length of a bit vector and the _absence_ of a "feature" bit. Add helpers for both KVM and "this CPU", and use the newfangled magic (along with X86_PROPERTY_*) to clean up pmu_event_filter_test. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add X86_PROPERTY_PMU_VERSION and use it in vmx_pmu_caps_test to replace open coded versions of the same functionality. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add and use x86 "properties" for the myriad AMX CPUID values that are validated by the AMX test. Drop most of the test's single-usage helpers so that the asserts more precisely capture what check failed. Signed-off-by:
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Sean Christopherson authored
Extent X86_PROPERTY_* support to KVM, i.e. add kvm_cpu_property() and kvm_cpu_has_p(), and use the new helpers in kvm_get_cpu_address_width(). No functional change intended. Signed-off-by:
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Sean Christopherson authored
Refactor kvm_cpuid_has() to prepare for extending X86_PROPERTY_* support to KVM as well as "this CPU". No functional change intended. Signed-off-by:
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Sean Christopherson authored
Use X86_PROPERTY_MAX_KVM_LEAF to replace the equivalent open coded check on KVM's maximum paravirt CPUID leaf. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Introduce X86_PROPERTY_* to allow retrieving values/properties from CPUID leafs, e.g. MAXPHYADDR from CPUID.0x80000008. Use the same core code as X86_FEATURE_*, the primary difference is that properties are multi-bit values, whereas features enumerate a single bit. Add this_cpu_has_p() to allow querying whether or not a property exists based on the maximum leaf associated with the property, e.g. MAXPHYADDR doesn't exist if the max leaf for 0x8000_xxxx is less than 0x8000_0008. Use the new property infrastructure in vm_compute_max_gfn() to prove that the code works as intended. Future patches will convert additional selftests code. Signed-off-by:
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Sean Christopherson authored
Refactor the X86_FEATURE_* framework to prepare for extending the core logic to support "properties". The "feature" framework allows querying a single CPUID bit to detect the presence of a feature; the "property" framework will extend the idea to allow querying a value, i.e. to get a value that is a set of contiguous bits in a CPUID leaf. Opportunistically add static asserts to ensure features are fully defined at compile time, and to try and catch mistakes in the definition of features. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add X86_FEATURE_PAE and use it to guesstimate the MAXPHYADDR when the MAXPHYADDR CPUID entry isn't supported. No functional change intended. Signed-off-by:
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David Matlack authored
Add a selftest to exercise the KVM_CAP_EXIT_ON_EMULATION_FAILURE capability. This capability is also exercised through smaller_maxphyaddr_emulation_test, but that test requires allow_smaller_maxphyaddr=Y, which is off by default on Intel when ept=Y and unconditionally disabled on AMD when npt=Y. This new test ensures that KVM_CAP_EXIT_ON_EMULATION_FAILURE is exercised independent of allow_smaller_maxphyaddr. Signed-off-by:
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David Matlack authored
Change smaller_maxphyaddr_emulation_test to expect a #PF(RSVD), rather than an emulation failure, when TDP is disabled. KVM only needs to emulate instructions to emulate a smaller guest.MAXPHYADDR when TDP is enabled. Fixes: 39bbcc3a ("selftests: kvm: Allows userspace to handle emulation errors.") Signed-off-by:
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Sean Christopherson authored
Provide the error code on a fault in KVM_ASM_SAFE(), e.g. to allow tests to assert that #PF generates the correct error code without needing to manually install a #PF handler. Use r10 as the scratch register for the error code, as it's already clobbered by the asm blob (loaded with the RIP of the to-be-executed instruction). Deliberately load the output "error_code" even in the non-faulting path so that error_code is always initialized with deterministic data (the aforementioned RIP), i.e to ensure a selftest won't end up with uninitialized consumption regardless of how KVM_ASM_SAFE() is used. Don't clear r10 in the non-faulting case and instead load error code with the RIP (see above). The error code is valid if and only if an exception occurs, and '0' isn't necessarily a better "invalid" value, e.g. '0' could result in false passes for a buggy test. Signed-off-by:
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Sean Christopherson authored
Clear R9 in the non-faulting path of KVM_ASM_SAFE() and fall through to to a common load of "vector" to effectively load "vector" with '0' to reduce the code footprint of the asm blob, to reduce the runtime overhead of the non-faulting path (when "vector" is stored in a register), and so that additional output constraints that are valid if and only if a fault occur are loaded even in the non-faulting case. A future patch will add a 64-bit output for the error code, and if its output is not explicitly loaded with _something_, the user of the asm blob can end up technically consuming uninitialized data. Using a common path to load the output constraints will allow using an existing scratch register, e.g. r10, to hold the error code in the faulting path, while also guaranteeing the error code is initialized with deterministic data in the non-faulting patch (r10 is loaded with the RIP of to-be-executed instruction). Consuming the error code when a fault doesn't occur would obviously be a test bug, but there's no guarantee the compiler will detect uninitialized consumption. And conversely, it's theoretically possible that the compiler might throw a false positive on uninitialized data, e.g. if the compiler can't determine that the non-faulting path won't touch the error code. Alternatively, the error code could be explicitly loaded in the non-faulting path, but loading a 64-bit memory|register output operand with an explicitl value requires a sign-extended "MOV imm32, r/m64", which isn't exactly straightforward and has a largish code footprint. And loading the error code with what is effectively garbage (from a scratch register) avoids having to choose an arbitrary value for the non-faulting case. Opportunistically remove a rogue asterisk in the block comment. Signed-off-by:
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David Matlack authored
Copy KVM's macros for page fault error masks into processor.h so they can be used in selftests. Signed-off-by:
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David Matlack authored
Use the preferred BIT() and BIT_ULL() to construct the PFERR masks rather than open-coding the bit shifting. No functional change intended. Signed-off-by:
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David Matlack authored
Move the flds instruction emulation failure handling code to a header so it can be re-used in an upcoming test. No functional change intended. Signed-off-by:
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David Matlack authored
Delete a bunch of code related to ucall handling from smaller_maxphyaddr_emulation_test. The only thing smaller_maxphyaddr_emulation_test needs to check is that the vCPU exits with UCALL_DONE after the second vcpu_run(). Signed-off-by:
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David Matlack authored
Hard-code the flds instruction and assert the exact instruction bytes are present in run->emulation_failure. The test already requires the instruction bytes to be present because that's the only way the test will advance the RIP past the flds and get to GUEST_DONE(). Note that KVM does not necessarily return exactly 2 bytes in run->emulation_failure since it may not know the exact instruction length in all cases. So just assert that run->emulation_failure.insn_size is at least 2. Signed-off-by:
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David Matlack authored
Rename emulator_error_test to smaller_maxphyaddr_emulation_test and update the comment at the top of the file to document that this is explicitly a test to validate that KVM emulates instructions in response to an EPT violation when emulating a smaller MAXPHYADDR. Signed-off-by:
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Gautam Menghani authored
In xapic_state_test's test_icr(), explicitly skip iterations that would match vcpu->id instead of assuming vcpu->id is '0', so that IPIs are are correctly sent to non-existent vCPUs. Suggested-by:
Gautam Menghani <gautammenghani201@gmail.com> Link: https://lore.kernel.org/r/20221017175819.12672-1-gautammenghani201@gmail.com [sean: massage shortlog and changelog] Signed-off-by:
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