- 17 Nov, 2022 40 commits
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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:
Paolo Bonzini <pbonzini@redhat.com>
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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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Vishal Annapurve authored
Add arch specific API kvm_arch_vm_post_create to perform any required setup after VM creation. Suggested-by:
Andrew Jones <andrew.jones@linux.dev> Reviewed-by:
Peter Gonda <pgonda@google.com> Signed-off-by:
Vishal Annapurve <vannapurve@google.com> Link: https://lore.kernel.org/r/20221115213845.3348210-4-vannapurve@google.com [sean: place x86's implementation by vm_arch_vcpu_add()] Signed-off-by:
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Vishal Annapurve authored
Introduce arch specific API: kvm_selftest_arch_init to allow each arch to handle initialization before running any selftest logic. Suggested-by:
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Vishal Annapurve authored
Consolidate common startup logic in one place by implementing a single setup function with __attribute((constructor)) for all selftests within kvm_util.c. This allows moving logic like: /* Tell stdout not to buffer its content */ setbuf(stdout, NULL); to a single file for all selftests. This will also allow any required setup at entry in future to be done in common main function. Link: https://lore.kernel.org/lkml/Ywa9T+jKUpaHLu%2Fl@google.comSuggested-by: -
Sean Christopherson authored
Play nice with huge pages when getting PTEs and translating GVAs to GPAs, there's no reason to disallow using huge pages in selftests. Use PG_LEVEL_NONE to indicate that the caller doesn't care about the mapping level and just wants to get the pte+level. Signed-off-by:
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Sean Christopherson authored
Use vm_get_page_table_entry() in addr_arch_gva2gpa() to get the leaf PTE instead of manually walking page tables. Signed-off-by:
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Sean Christopherson authored
Use virt_get_pte() in vm_get_page_table_entry() instead of open coding equivalent code. Signed-off-by:
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Sean Christopherson authored
Verify the parent PTE is PRESENT when getting a child via virt_get_pte() so that the helper can be used for getting PTEs/GPAs without losing sanity checks that the walker isn't wandering into the weeds. Signed-off-by:
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Sean Christopherson authored
Remove the pointless shift from GPA=>GFN and immediately back to GFN=>GPA when creating guest page tables. Ignore the other walkers that have a similar pattern for the moment, they will be converted to use virt_get_pte() in the near future. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Drop the reserved bit checks from the helper to retrieve a PTE, there's very little value in sanity checking the constructed page tables as any will quickly be noticed in the form of an unexpected #PF. The checks also place unnecessary restrictions on the usage of the helpers, e.g. if a test _wanted_ to set reserved bits for whatever reason. Removing the NX check in particular allows for the removal of the @vcpu param, which will in turn allow the helper to be reused nearly verbatim for addr_gva2gpa(). Signed-off-by:
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Sean Christopherson authored
Drop vm_{g,s}et_page_table_entry() and instead expose the "inner" helper (was _vm_get_page_table_entry()) that returns a _pointer_ to the PTE, i.e. let tests directly modify PTEs instead of bouncing through helpers that just make life difficult. Opportunsitically use BIT_ULL() in emulator_error_test, and use the MAXPHYADDR define to set the "rogue" GPA bit instead of open coding the same value. No functional change intended. Signed-off-by: -
Colin Ian King authored
There is a spelling mistake in an assert message. Fix it. Signed-off-by:
Colin Ian King <colin.i.king@gmail.com> Reviewed-by:
Jim Mattson <jmattson@google.com> Link: https://lore.kernel.org/r/20220928213458.64089-1-colin.i.king@gmail.com [sean: fix an ironic typo in the changelog] Signed-off-by:
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