- 20 Jun, 2022 37 commits
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Sean Christopherson authored
Add x86-64 support for exception fixup on single instructions, without forcing tests to install their own fault handlers. Use registers r9-r11 to flag the instruction as "safe" and pass fixup/vector information, i.e. introduce yet another flavor of fixup (versus the kernel's in-memory tables and KUT's per-CPU area) to take advantage of KVM sefltests being 64-bit only. Using only registers avoids the need to allocate fixup tables, ensure FS or GS base is valid for the guest, ensure memory is mapped into the guest, etc..., and also reduces the potential for recursive faults due to accessing memory. Providing exception fixup trivializes tests that just want to verify that an instruction faults, e.g. no need to track start/end using global labels, no need to install a dedicated handler, etc... Deliberately do not support #DE in exception fixup so that the fixup glue doesn't need to account for a fault with vector == 0, i.e. the vector can also indicate that a fault occurred. KVM injects #DE only for esoteric emulation scenarios, i.e. there's very, very little value in testing #DE. Force any test that wants to generate #DEs to install its own handler(s). Use kvm_pv_test as a guinea pig for the new fixup, as it has a very straightforward use case of wanting to verify that RDMSR and WRMSR fault. Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20220608224516.3788274-3-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Sean Christopherson authored
Add a quirk for KVM's behavior of emulating intercepted MONITOR/MWAIT instructions a NOPs regardless of whether or not they are supported in guest CPUID. KVM's current behavior was likely motiviated by a certain fruity operating system that expects MONITOR/MWAIT to be supported unconditionally and blindly executes MONITOR/MWAIT without first checking CPUID. And because KVM does NOT advertise MONITOR/MWAIT to userspace, that's effectively the default setup for any VMM that regurgitates KVM_GET_SUPPORTED_CPUID to KVM_SET_CPUID2. Note, this quirk interacts with KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT. The behavior is actually desirable, as userspace VMMs that want to unconditionally hide MONITOR/MWAIT from the guest can leave the MISC_ENABLE quirk enabled. Signed-off-by:
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Sean Christopherson authored
Ignore host userspace writes of '0' to F15H_PERF_CTL MSRs KVM reports in the MSR-to-save list, but the MSRs are ultimately unsupported. All MSRs in said list must be writable by userspace, e.g. if userspace sends the list back at KVM without filtering out the MSRs it doesn't need. Note, reads of said MSRs already have the desired behavior. Signed-off-by:
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Sean Christopherson authored
Ignore host userspace reads and writes of '0' to PEBS and BTS MSRs that KVM reports in the MSR-to-save list, but the MSRs are ultimately unsupported. All MSRs in said list must be writable by userspace, e.g. if userspace sends the list back at KVM without filtering out the MSRs it doesn't need. Fixes: 8183a538 ("KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to support guest DS") Fixes: 902caeb6 ("KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS") Fixes: c59a1f10 ("KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS") Signed-off-by:
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Sean Christopherson authored
Use vcpu_get_perf_capabilities() when querying MSR_IA32_PERF_CAPABILITIES from the guest's perspective, e.g. to update the vPMU and to determine which MSRs exist. If userspace ignores MSR_IA32_PERF_CAPABILITIES but clear X86_FEATURE_PDCM, the guest should see '0'. Fixes: 902caeb6 ("KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS") Fixes: c59a1f10 ("KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS") Signed-off-by:
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Sean Christopherson authored
Revert the hack to allow host-initiated accesses to all "PMU" MSRs, as intel_is_valid_msr() returns true for _all_ MSRs, regardless of whether or not it has a snowball's chance in hell of actually being a PMU MSR. That mostly gets papered over by the actual get/set helpers only handling MSRs that they knows about, except there's the minor detail that kvm_pmu_{g,s}et_msr() eat reads and writes when the PMU is disabled. I.e. KVM will happy allow reads and writes to _any_ MSR if the PMU is disabled, either via module param or capability. This reverts commit d1c88a40. Fixes: d1c88a40 ("KVM: x86: always allow host-initiated writes to PMU MSRs") Signed-off-by: -
Sean Christopherson authored
Eating reads and writes to all "PMU" MSRs when there is no PMU is wildly broken as it results in allowing accesses to _any_ MSR on Intel CPUs as intel_is_valid_msr() returns true for all host_initiated accesses. A revert of commit d1c88a40 ("KVM: x86: always allow host-initiated writes to PMU MSRs") will soon follow. This reverts commit 8e6a58e2. Signed-off-by:
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Sean Christopherson authored
Do not clear manipulate MSR_IA32_PERF_CAPABILITIES in intel_pmu_refresh(), i.e. give userspace full control over capability/read-only MSRs. KVM is not a babysitter, it is userspace's responsiblity to provide a valid and coherent vCPU model. Attempting to "help" the guest by forcing a consistent model creates edge cases, and ironicially leads to inconsistent behavior. Example #1: KVM doesn't do intel_pmu_refresh() when userspace writes the MSR. Example #2: KVM doesn't clear the bits when the PMU is disabled, or when there's no architectural PMU. Signed-off-by:
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Sean Christopherson authored
Give userspace full control of the read-only bits in MISC_ENABLES, i.e. do not modify bits on PMU refresh and do not preserve existing bits when userspace writes MISC_ENABLES. With a few exceptions where KVM doesn't expose the necessary controls to userspace _and_ there is a clear cut association with CPUID, e.g. reserved CR4 bits, KVM does not own the vCPU and should not manipulate the vCPU model on behalf of "dummy user space". The argument that KVM is doing userspace a favor because "the order of setting vPMU capabilities and MSR_IA32_MISC_ENABLE is not strictly guaranteed" is specious, as attempting to configure MSRs on behalf of userspace inevitably leads to edge cases precisely because KVM does not prescribe a specific order of initialization. Example #1: intel_pmu_refresh() consumes and modifies the vCPU's MSR_IA32_PERF_CAPABILITIES, and so assumes userspace initializes config MSRs before setting the guest CPUID model. If userspace sets CPUID first, then KVM will mark PEBS as available when arch.perf_capabilities is initialized with a non-zero PEBS format, thus creating a bad vCPU model if userspace later disables PEBS by writing PERF_CAPABILITIES. Example #2: intel_pmu_refresh() does not clear PERF_CAP_PEBS_MASK in MSR_IA32_PERF_CAPABILITIES if there is no vPMU, making KVM inconsistent in its desire to be consistent. Example #3: intel_pmu_refresh() does not clear MSR_IA32_MISC_ENABLE_EMON if KVM_SET_CPUID2 is called multiple times, first with a vPMU, then without a vPMU. While slightly contrived, it's plausible a VMM could reflect KVM's default vCPU and then operate on KVM's copy of CPUID to later clear the vPMU settings, e.g. see KVM's selftests. Example #4: Enumerating an Intel vCPU on an AMD host will not call into intel_pmu_refresh() at any point, and so the BTS and PEBS "unavailable" bits will be left clear, without any way for userspace to set them. Keep the "R" behavior of the bit 7, "EMON available", for the guest. Unlike the BTS and PEBS bits, which are fully "RO", the EMON bit can be written with a different value, but that new value is ignored. Cc: Like Xu <likexu@tencent.com> Signed-off-by:
kernel test robot <oliver.sang@intel.com> Message-Id: <20220611005755.753273-2-seanjc@google.com> Signed-off-by:
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Dongliang Mu authored
kfree can handle NULL pointer as its argument. According to coccinelle isnullfree check, remove NULL check before kfree operation. Signed-off-by:
Dongliang Mu <mudongliangabcd@gmail.com> Message-Id: <20220614133458.147314-1-dzm91@hust.edu.cn> Signed-off-by:
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Sean Christopherson authored
Drop the unnecessary initialization of the local 'pfn' variable in hva_to_pfn(). First and foremost, '0' is not an invalid pfn, it's a perfectly valid pfn on most architectures. I.e. if hva_to_pfn() were to return an "uninitializd" pfn, it would actually be interpeted as a legal pfn by most callers. Second, hva_to_pfn() can't return an uninitialized pfn as hva_to_pfn() explicitly sets pfn to an error value (or returns an error value directly) if a helper returns failure, and all helpers set the pfn on success. The zeroing of 'pfn' was introduced by commit 2fc84311 ("KVM: reorganize hva_to_pfn"), probably to avoid "uninitialized variable" warnings on statements that return pfn. However, no compiler seems to produce them, making the initialization unnecessary. Signed-off-by:
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Sean Christopherson authored
Move the check that restricts mapping huge pages into the guest to pfns that are backed by refcounted 'struct page' memory into the helper that actually "requires" a 'struct page', host_pfn_mapping_level(). In addition to deduplicating code, moving the check to the helper eliminates the subtle requirement that the caller check that the incoming pfn is backed by a refcounted struct page, and as an added bonus avoids an extra pfn_to_page() lookup. Note, the is_error_noslot_pfn() check in kvm_mmu_hugepage_adjust() needs to stay where it is, as it guards against dereferencing a NULL memslot in the kvm_slot_dirty_track_enabled() that follows. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Rename and refactor kvm_is_reserved_pfn() to kvm_pfn_to_refcounted_page() to better reflect what KVM is actually checking, and to eliminate extra pfn_to_page() lookups. The kvm_release_pfn_*() an kvm_try_get_pfn() helpers in particular benefit from "refouncted" nomenclature, as it's not all that obvious why KVM needs to get/put refcounts for some PG_reserved pages (ZERO_PAGE and ZONE_DEVICE). Add a comment to call out that the list of exceptions to PG_reserved is all but guaranteed to be incomplete. The list has mostly been compiled by people throwing noodles at KVM and finding out they stick a little too well, e.g. the ZERO_PAGE's refcount overflowed and ZONE_DEVICE pages didn't get freed. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Operate on a 'struct page' instead of a pfn when checking if a page is a ZONE_DEVICE page, and rename the helper accordingly. Generally speaking, KVM doesn't actually care about ZONE_DEVICE memory, i.e. shouldn't do anything special for ZONE_DEVICE memory. Rather, KVM wants to treat ZONE_DEVICE memory like regular memory, and the need to identify ZONE_DEVICE memory only arises as an exception to PG_reserved pages. In other words, KVM should only ever check for ZONE_DEVICE memory after KVM has already verified that there is a struct page associated with the pfn. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Drop helpers to convert a gfn/gpa to a 'struct page' in the context of a vCPU. KVM doesn't require that guests be backed by 'struct page' memory, thus any use of helpers that assume 'struct page' is bound to be flawed, as was the case for the recently removed last user in x86's nested VMX. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Drop a WARN_ON() if kvm_pfn_to_page() encounters a "reserved" pfn, which in this context means a struct page that has PG_reserved but is not a/the ZERO_PAGE and is not a ZONE_DEVICE page. The usage, via gfn_to_page(), in x86 is safe as gfn_to_page() is used only to retrieve a page from KVM-controlled memslot, but the usage in PPC and s390 operates on arbitrary gfns and thus memslots that can be backed by incompatible memory. Signed-off-by:
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Sean Christopherson authored
Use kvm_vcpu_map() to get/pin the backing for vmcs12's APIC-access page, there's no reason it has to be restricted to 'struct page' backing. The APIC-access page actually doesn't need to be backed by anything, which is ironically why it got left behind by the series which introduced kvm_vcpu_map()[1]; the plan was to shove a dummy pfn into vmcs02[2], but that code never got merged. Switching the APIC-access page to kvm_vcpu_map() doesn't preclude using a magic pfn in the future, and will allow a future patch to drop kvm_vcpu_gpa_to_page(). [1] https://lore.kernel.org/all/1547026933-31226-1-git-send-email-karahmed@amazon.de [2] https://lore.kernel.org/lkml/1543845551-4403-1-git-send-email-karahmed@amazon.deSigned-off-by:
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Sean Christopherson authored
Invert the order of KVM's page/pfn release helpers so that the "inner" helper operates on a page instead of a pfn. As pointed out by Linus[*], converting between struct page and a pfn isn't necessarily cheap, and that's not even counting the overhead of is_error_noslot_pfn() and kvm_is_reserved_pfn(). Even if the checks were dirt cheap, there's no reason to convert from a page to a pfn and back to a page, just to mark the page dirty/accessed or to put a reference to the page. Opportunistically drop a stale declaration of kvm_set_page_accessed() from kvm_host.h (there was no implementation). No functional change intended. [*] https://lore.kernel.org/all/CAHk-=wifQimj2d6npq-wCi5onYPjzQg4vyO4tFcPJJZr268cRw@mail.gmail.comSigned-off-by:
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Sean Christopherson authored
Don't set Accessed/Dirty bits for a struct page with PG_reserved set, i.e. don't set A/D bits for the ZERO_PAGE. The ZERO_PAGE (or pages depending on the architecture) should obviously never be written, and similarly there's no point in marking it accessed as the page will never be swapped out or reclaimed. The comment in page-flags.h is quite clear that PG_reserved pages should be managed only by their owner, and strictly following that mandate also simplifies KVM's logic. Fixes: 7df003c8 ("KVM: fix overflow of zero page refcount with ksm running") Signed-off-by:
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Sean Christopherson authored
Remove a check from kvm_release_pfn() to bail if the provided @pfn is zero. Zero is a perfectly valid pfn on most architectures, and should not be used to indicate an error or an invalid pfn. The bogus check was added by commit 91724814 ("x86/kvm: Cache gfn to pfn translation"), which also did the bad thing of zeroing the pfn and gfn to mark a cache invalid. Thankfully, that bad behavior was axed by commit 357a18ad ("KVM: Kill kvm_map_gfn() / kvm_unmap_gfn() and gfn_to_pfn_cache"). Signed-off-by:
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Sean Christopherson authored
Use common logic for computing PT_BASE_ADDR_MASK for 32-bit, 64-bit, and EPT paging. Both PAGE_MASK and the new-common logic are supsersets of what is actually needed for 32-bit paging. PAGE_MASK sets bits 63:12 and the former GUEST_PT64_BASE_ADDR_MASK sets bits 51:12, so regardless of which value is used, the result will always be bits 31:12. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Truncate paging32's PT_BASE_ADDR_MASK to a pt_element_t, i.e. to 32 bits. Ignoring PSE huge pages, the mask is only used in conjunction with gPTEs, which are 32 bits, and so the address is limited to bits 31:12. PSE huge pages encoded PA bits 39:32 in PTE bits 20:13, i.e. need custom logic to handle their funky encoding regardless of PT_BASE_ADDR_MASK. Note, PT_LVL_OFFSET_MASK is somewhat confusing in that it computes the offset of the _gfn_, not of the gpa, i.e. not having bits 63:32 set in PT_BASE_ADDR_MASK is again correct. No functional change intended. Signed-off-by:
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Paolo Bonzini authored
Dedup the code for generating (most of) the per-type PT_* masks in paging_tmpl.h. The relevant macros only vary based on the number of bits per level, and that smidge of info is already provided in a common form as PT_LEVEL_BITS. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Separate the macros for KVM's shadow PTEs (SPTE) from guest 64-bit PTEs (PT64). SPTE and PT64 are _mostly_ the same, but the few differences are quite critical, e.g. *_BASE_ADDR_MASK must differentiate between host and guest physical address spaces, and SPTE_PERM_MASK (was PT64_PERM_MASK) is very much specific to SPTEs. Opportunistically (and temporarily) move most guest macros into paging.h to clearly associate them with shadow paging, and to ensure that they're not used as of this commit. A future patch will eliminate them entirely. Sadly, PT32_LEVEL_BITS is left behind in mmu_internal.h because it's needed for the quadrant calculation in kvm_mmu_get_page(). The quadrant calculation is hot enough (when using shadow paging with 32-bit guests) that adding a per-context helper is undesirable, and burying the computation in paging_tmpl.h with a forward declaration isn't exactly an improvement. Signed-off-by:
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Sean Christopherson authored
Provide common helper macros to generate various masks, shifts, etc... for 32-bit vs. 64-bit page tables. Only the inputs differ, the actual calculations are identical. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Move a handful of one-off macros and helpers for 32-bit PSE paging into paging_tmpl.h and hide them behind "PTTYPE == 32". Under no circumstance should anything but 32-bit shadow paging care about PSE paging. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Compute the number of PTEs to be filled for the 32-bit PSE page tables using the page size and the size of each entry. While using the MMU's PT32_ENT_PER_PAGE macro is arguably better in isolation, removing VMX's usage will allow a future namespacing cleanup to move the guest page table macros into paging_tmpl.h, out of the reach of code that isn't directly related to shadow paging. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Use lapic_in_kernel() in kvm_vcpu_apicv_active() to take advantage of the kvm_has_noapic_vcpu static branch. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Move the per-vCPU apicv_active flag into KVM's local APIC instance. APICv is fully dependent on an in-kernel local APIC, but that's not at all clear when reading the current code due to the flag being stored in the generic kvm_vcpu_arch struct. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Use kvm_vcpu_apicv_active() to check if APICv is active when seeing if a vCPU is a candidate for directed yield due to a pending ACPIv interrupt. This will allow moving apicv_active into kvm_lapic without introducing a potential NULL pointer deref (kvm_vcpu_apicv_active() effectively adds a pre-check on the vCPU having an in-kernel APIC). No functional change intended. Signed-off-by:
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Sean Christopherson authored
Drop the unused @vcpu parameter from hwapic_isr_update(). AMD/AVIC is unlikely to implement the helper, and VMX/APICv doesn't need the vCPU as it operates on the current VMCS. The result is somewhat odd, but allows for a decent amount of (future) cleanup in the APIC code. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Drop a handful of unused AVIC function declarations whose implementations were removed during the conversion to optional static calls. No functional change intended. Fixes: abb6d479 ("KVM: x86: make several APIC virtualization callbacks optional") Signed-off-by:
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Sean Christopherson authored
Update vmcs12->guest_bndcfgs on intercepted writes to BNDCFGS from L2 instead of waiting until vmcs02 is synchronized to vmcs12. KVM always intercepts BNDCFGS accesses, so the only way the value in vmcs02 can change is via KVM's explicit VMWRITE during emulation. Signed-off-by:
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Sean Christopherson authored
Save BNDCFGS to vmcs12 (from vmcs02) if and only if at least of one of the load-on-entry or clear-on-exit fields for BNDCFGS is enumerated as an allowed-1 bit in vmcs12. Skipping the field avoids an unnecessary VMREAD when MPX is supported but not exposed to L1. Per Intel's SDM: If the processor supports either the 1-setting of the "load IA32_BNDCFGS" VM-entry control or that of the "clear IA32_BNDCFGS" VM-exit control, the contents of the IA32_BNDCFGS MSR are saved into the corresponding field. Signed-off-by:
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Sean Christopherson authored
Rename the fields in struct nested_vmx used to snapshot pre-VM-Enter values to reflect that they can hold L2's values when restoring nested state, e.g. if userspace restores MSRs before nested state. As crazy as it seems, restoring MSRs before nested state actually works (because KVM goes out if it's way to make it work), even though the initial MSR writes will hit vmcs01 despite holding L2 values. Add a related comment to vmx_enter_smm() to call out that using the common VM-Exit and VM-Enter helpers to emulate SMI and RSM is wrong and broken. The few MSRs that have snapshots _could_ be fixed by taking a snapshot prior to the forced VM-Exit instead of at forced VM-Enter, but that's just the tip of the iceberg as the rather long list of MSRs that aren't snapshotted (hello, VM-Exit MSR load list) can't be handled this way. Signed-off-by:
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Sean Christopherson authored
If a nested run isn't pending, snapshot vmcs01.GUEST_IA32_DEBUGCTL irrespective of whether or not VM_ENTRY_LOAD_DEBUG_CONTROLS is set in vmcs12. When restoring nested state, e.g. after migration, without a nested run pending, prepare_vmcs02() will propagate nested.vmcs01_debugctl to vmcs02, i.e. will load garbage/zeros into vmcs02.GUEST_IA32_DEBUGCTL. If userspace restores nested state before MSRs, then loading garbage is a non-issue as loading DEBUGCTL will also update vmcs02. But if usersepace restores MSRs first, then KVM is responsible for propagating L2's value, which is actually thrown into vmcs01, into vmcs02. Restoring L2 MSRs into vmcs01, i.e. loading all MSRs before nested state is all kinds of bizarre and ideally would not be supported. Sadly, some VMMs do exactly that and rely on KVM to make things work. Note, there's still a lurking SMM bug, as propagating vmcs01's DEBUGCTL to vmcs02 across RSM may corrupt L2's DEBUGCTL. But KVM's entire VMX+SMM emulation is flawed as SMI+RSM should not toouch _any_ VMCS when use the "default treatment of SMIs", i.e. when not using an SMI Transfer Monitor. Link: https://lore.kernel.org/all/Yobt1XwOfb5M6Dfa@google.com Fixes: 8fcc4b59 ("kvm: nVMX: Introduce KVM_CAP_NESTED_STATE") Cc: stable@vger.kernel.org Signed-off-by:
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Sean Christopherson authored
If a nested run isn't pending, snapshot vmcs01.GUEST_BNDCFGS irrespective of whether or not VM_ENTRY_LOAD_BNDCFGS is set in vmcs12. When restoring nested state, e.g. after migration, without a nested run pending, prepare_vmcs02() will propagate nested.vmcs01_guest_bndcfgs to vmcs02, i.e. will load garbage/zeros into vmcs02.GUEST_BNDCFGS. If userspace restores nested state before MSRs, then loading garbage is a non-issue as loading BNDCFGS will also update vmcs02. But if usersepace restores MSRs first, then KVM is responsible for propagating L2's value, which is actually thrown into vmcs01, into vmcs02. Restoring L2 MSRs into vmcs01, i.e. loading all MSRs before nested state is all kinds of bizarre and ideally would not be supported. Sadly, some VMMs do exactly that and rely on KVM to make things work. Note, there's still a lurking SMM bug, as propagating vmcs01.GUEST_BNDFGS to vmcs02 across RSM may corrupt L2's BNDCFGS. But KVM's entire VMX+SMM emulation is flawed as SMI+RSM should not toouch _any_ VMCS when use the "default treatment of SMIs", i.e. when not using an SMI Transfer Monitor. Link: https://lore.kernel.org/all/Yobt1XwOfb5M6Dfa@google.com Fixes: 62cf9bd8 ("KVM: nVMX: Fix emulation of VM_ENTRY_LOAD_BNDCFGS") Cc: stable@vger.kernel.org Cc: Lei Wang <lei4.wang@intel.com> Signed-off-by:
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- 15 Jun, 2022 3 commits
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Uros Bizjak authored
Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in fast_pf_fix_direct_spte. cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Signed-off-by:
Uros Bizjak <ubizjak@gmail.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Wanpeng Li <wanpengli@tencent.com> Cc: Jim Mattson <jmattson@google.com> Cc: Joerg Roedel <joro@8bytes.org> Message-Id: <20220520144635.63134-1-ubizjak@gmail.com> Signed-off-by:
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Uros Bizjak authored
Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in pi_try_set_control. cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg): b9: 88 44 24 60 mov %al,0x60(%rsp) bd: 48 89 c8 mov %rcx,%rax c0: c6 44 24 62 f2 movb $0xf2,0x62(%rsp) c5: 48 8b 74 24 60 mov 0x60(%rsp),%rsi ca: f0 49 0f b1 34 24 lock cmpxchg %rsi,(%r12) d0: 48 39 c1 cmp %rax,%rcx d3: 75 cf jne a4 <vmx_vcpu_pi_load+0xa4> patched: c1: 88 54 24 60 mov %dl,0x60(%rsp) c5: c6 44 24 62 f2 movb $0xf2,0x62(%rsp) ca: 48 8b 54 24 60 mov 0x60(%rsp),%rdx cf: f0 48 0f b1 13 lock cmpxchg %rdx,(%rbx) d4: 75 d5 jne ab <vmx_vcpu_pi_load+0xab> Signed-off-by:
kernel test robot <lkp@intel.com> Message-Id: <20220520143737.62513-1-ubizjak@gmail.com> Signed-off-by:
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Uros Bizjak authored
Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in tdp_mmu_set_spte_atomic. cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, remove explicit assignment to iter->old_spte when cmpxchg fails, this is what try_cmpxchg does implicitly. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <seanjc@google.com> Signed-off-by:
David Matlack <dmatlack@google.com> Message-Id: <20220518135111.3535-1-ubizjak@gmail.com> Signed-off-by:
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