- 08 Jul, 2022 3 commits
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Sean Christopherson authored
Add helpers to identify CTL (control) and STATUS MCi MSR types instead of open coding the checks using the offset. Using the offset is perfectly safe, but unintuitive, as understanding what the code does requires knowing that the offset calcuation will not affect the lower three bits. Opportunistically comment the STATUS logic to save readers a trip to Intel's SDM or AMD's APM to understand the "data != 0" check. No functional change intended. Signed-off-by:
Sean Christopherson <seanjc@google.com> Reviewed-by:
Jim Mattson <jmattson@google.com> Link: https://lore.kernel.org/r/20220512222716.4112548-4-seanjc@google.com
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Sean Christopherson authored
Use an explicit case statement to grab the full range of MCx bank MSRs in {g,s}et_msr_mce(), and manually check only the "end" (the number of banks configured by userspace may be less than the max). The "default" trick works, but is a bit odd now, and will be quite odd if/when support for accessing MCx_CTL2 MSRs is added, which has near identical logic. Hoist "offset" to function scope so as to avoid curly braces for the case statement, and because MCx_CTL2 support will need the same variables. Opportunstically clean up the comment about allowing bit 10 to be cleared from bank 4. No functional change intended. Cc: Jue Wang <juew@google.com> Signed-off-by: -
Sean Christopherson authored
Return '1', not '-1', when handling an illegal WRMSR to a MCi_CTL or MCi_STATUS MSR. The behavior of "all zeros' or "all ones" for CTL MSRs is architectural, as is the "only zeros" behavior for STATUS MSRs. I.e. the intent is to inject a #GP, not exit to userspace due to an unhandled emulation case. Returning '-1' gets interpreted as -EPERM up the stack and effecitvely kills the guest. Fixes: 890ca9ae ("KVM: Add MCE support") Fixes: 9ffd986c ("KVM: X86: #GP when guest attempts to write MCi_STATUS register w/o 0") Cc: stable@vger.kernel.org Signed-off-by:
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- 24 Jun, 2022 33 commits
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Paolo Bonzini authored
The TLB flush before installing the newly-populated lower level page table is unnecessary if the lower-level page table maps the huge page identically. KVM knows it is if it did not reuse an existing shadow page table, tell drop_large_spte() to skip the flush in that case. Extracted from a patch by David Matlack. Signed-off-by:Paolo Bonzini <pbonzini@redhat.com>
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David Matlack authored
Add support for Eager Page Splitting pages that are mapped by nested MMUs. Walk through the rmap first splitting all 1GiB pages to 2MiB pages, and then splitting all 2MiB pages to 4KiB pages. Note, Eager Page Splitting is limited to nested MMUs as a policy rather than due to any technical reason (the sp->role.guest_mode check could just be deleted and Eager Page Splitting would work correctly for all shadow MMU pages). There is really no reason to support Eager Page Splitting for tdp_mmu=N, since such support will eventually be phased out, and there is no current use case supporting Eager Page Splitting on hosts where TDP is either disabled or unavailable in hardware. Furthermore, future improvements to nested MMU scalability may diverge the code from the legacy shadow paging implementation. These improvements will be simpler to make if Eager Page Splitting does not have to worry about legacy shadow paging. Splitting huge pages mapped by nested MMUs requires dealing with some extra complexity beyond that of the TDP MMU: (1) The shadow MMU has a limit on the number of shadow pages that are allowed to be allocated. So, as a policy, Eager Page Splitting refuses to split if there are KVM_MIN_FREE_MMU_PAGES or fewer pages available. (2) Splitting a huge page may end up re-using an existing lower level shadow page tables. This is unlike the TDP MMU which always allocates new shadow page tables when splitting. (3) When installing the lower level SPTEs, they must be added to the rmap which may require allocating additional pte_list_desc structs. Case (2) is especially interesting since it may require a TLB flush, unlike the TDP MMU which can fully split huge pages without any TLB flushes. Specifically, an existing lower level page table may point to even lower level page tables that are not fully populated, effectively unmapping a portion of the huge page, which requires a flush. As of this commit, a flush is always done always after dropping the huge page and before installing the lower level page table. This TLB flush could instead be delayed until the MMU lock is about to be dropped, which would batch flushes for multiple splits. However these flushes should be rare in practice (a huge page must be aliased in multiple SPTEs and have been split for NX Huge Pages in only some of them). Flushing immediately is simpler to plumb and also reduces the chances of tripping over a CPU bug (e.g. see iTLB multihit). [ This commit is based off of the original implementation of Eager Page Splitting from Peter in Google's kernel from 2016. ] Suggested-by:Peter Feiner <pfeiner@google.com> Signed-off-by:
David Matlack <dmatlack@google.com> Message-Id: <20220516232138.1783324-23-dmatlack@google.com> Signed-off-by:
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David Matlack authored
Allow the capacity of the kvm_mmu_memory_cache struct to be chosen at declaration time rather than being fixed for all declarations. This will be used in a follow-up commit to declare an cache in x86 with a capacity of 512+ objects without having to increase the capacity of all caches in KVM. This change requires each cache now specify its capacity at runtime, since the cache struct itself no longer has a fixed capacity known at compile time. To protect against someone accidentally defining a kvm_mmu_memory_cache struct directly (without the extra storage), this commit includes a WARN_ON() in kvm_mmu_topup_memory_cache(). In order to support different capacities, this commit changes the objects pointer array to be dynamically allocated the first time the cache is topped-up. While here, opportunistically clean up the stack-allocated kvm_mmu_memory_cache structs in riscv and arm64 to use designated initializers. No functional change intended. Reviewed-by:
Marc Zyngier <maz@kernel.org> Signed-off-by:
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Paolo Bonzini authored
Before allocating a child shadow page table, all callers check whether the parent already points to a huge page and, if so, they drop that SPTE. This is done by drop_large_spte(). However, dropping the large SPTE is really only necessary before the sp is installed. While the sp is returned by kvm_mmu_get_child_sp(), installing it happens later in __link_shadow_page(). Move the call there instead of having it in each and every caller. To ensure that the shadow page is not linked twice if it was present, do _not_ opportunistically make kvm_mmu_get_child_sp() idempotent: instead, return an error value if the shadow page already existed. This is a bit more verbose, but clearer than NULL. Finally, now that the drop_large_spte() name is not taken anymore, remove the two underscores in front of __drop_large_spte(). Reviewed-by:
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David Matlack authored
Currently KVM only zaps collapsible 4KiB SPTEs in the shadow MMU. This is fine for now since KVM never creates intermediate huge pages during dirty logging. In other words, KVM always replaces 1GiB pages directly with 4KiB pages, so there is no reason to look for collapsible 2MiB pages. However, this will stop being true once the shadow MMU participates in eager page splitting. During eager page splitting, each 1GiB is first split into 2MiB pages and then those are split into 4KiB pages. The intermediate 2MiB pages may be left behind if an error condition causes eager page splitting to bail early. No functional change intended. Reviewed-by:
Peter Xu <peterx@redhat.com> Signed-off-by:
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David Matlack authored
Currently make_huge_page_split_spte() assumes execute permissions can be granted to any 4K SPTE when splitting huge pages. This is true for the TDP MMU but is not necessarily true for the shadow MMU, since KVM may be shadowing a non-executable huge page. To fix this, pass in the role of the child shadow page where the huge page will be split and derive the execution permission from that. This is correct because huge pages are always split with direct shadow page and thus the shadow page role contains the correct access permissions. No functional change intended. Signed-off-by:
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David Matlack authored
Splitting huge pages requires allocating/finding shadow pages to replace the huge page. Shadow pages are keyed, in part, off the guest access permissions they are shadowing. For fully direct MMUs, there is no shadowing so the access bits in the shadow page role are always ACC_ALL. But during shadow paging, the guest can enforce whatever access permissions it wants. In particular, eager page splitting needs to know the permissions to use for the subpages, but KVM cannot retrieve them from the guest page tables because eager page splitting does not have a vCPU. Fortunately, the guest access permissions are easy to cache whenever page faults or FNAME(sync_page) update the shadow page tables; this is an extension of the existing cache of the shadowed GFNs in the gfns array of the shadow page. The access bits only take up 3 bits, which leaves 61 bits left over for gfns, which is more than enough. Now that the gfns array caches more information than just GFNs, rename it to shadowed_translation. While here, preemptively fix up the WARN_ON() that detects gfn mismatches in direct SPs. The WARN_ON() was paired with a pr_err_ratelimited(), which means that users could sometimes see the WARN without the accompanying error message. Fix this by outputting the error message as part of the WARN splat, and opportunistically make them WARN_ONCE() because if these ever fire, they are all but guaranteed to fire a lot and will bring down the kernel. Signed-off-by:
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David Matlack authored
Update the page stats in __rmap_add() rather than at the call site. This will avoid having to manually update page stats when splitting huge pages in a subsequent commit. No functional change intended. Reviewed-by:
Ben Gardon <bgardon@google.com> Reviewed-by:
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David Matlack authored
Allow adding new entries to the rmap and linking shadow pages without a struct kvm_vcpu pointer by moving the implementation of rmap_add() and link_shadow_page() into inner helper functions. No functional change intended. Reviewed-by:
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David Matlack authored
Constify rmap_add()'s @slot parameter; it is simply passed on to gfn_to_rmap(), which takes a const memslot. No functional change intended. Reviewed-by:
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David Matlack authored
Allow @vcpu to be NULL in kvm_mmu_find_shadow_page() (and its only caller __kvm_mmu_get_shadow_page()). @vcpu is only required to sync indirect shadow pages, so it's safe to pass in NULL when looking up direct shadow pages. This will be used for doing eager page splitting, which allocates direct shadow pages from the context of a VM ioctl without access to a vCPU pointer. Signed-off-by:
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David Matlack authored
Get the kvm pointer from the caller, rather than deriving it from vcpu->kvm, and plumb the kvm pointer all the way from kvm_mmu_get_shadow_page(). With this change in place, the vcpu pointer is only needed to sync indirect shadow pages. In other words, __kvm_mmu_get_shadow_page() can now be used to get *direct* shadow pages without a vcpu pointer. This enables eager page splitting, which needs to allocate direct shadow pages during VM ioctls. No functional change intended. Signed-off-by:
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David Matlack authored
The vcpu pointer in kvm_mmu_alloc_shadow_page() is only used to get the kvm pointer. So drop the vcpu pointer and just pass in the kvm pointer. No functional change intended. Signed-off-by:
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David Matlack authored
Refactor kvm_mmu_alloc_shadow_page() to receive the caches from which it will allocate the various pieces of memory for shadow pages as a parameter, rather than deriving them from the vcpu pointer. This will be useful in a future commit where shadow pages are allocated during VM ioctls for eager page splitting, and thus will use a different set of caches. Preemptively pull the caches out all the way to kvm_mmu_get_shadow_page() since eager page splitting will not be calling kvm_mmu_alloc_shadow_page() directly. No functional change intended. Signed-off-by:
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David Matlack authored
Move the code that write-protects newly-shadowed guest page tables into account_shadowed(). This avoids a extra gfn-to-memslot lookup and is a more logical place for this code to live. But most importantly, this reduces kvm_mmu_alloc_shadow_page()'s reliance on having a struct kvm_vcpu pointer, which will be necessary when creating new shadow pages during VM ioctls for eager page splitting. Note, it is safe to drop the role.level == PG_LEVEL_4K check since account_shadowed() returns early if role.level > PG_LEVEL_4K. No functional change intended. Reviewed-by:
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David Matlack authored
Rename 2 functions: kvm_mmu_get_page() -> kvm_mmu_get_shadow_page() kvm_mmu_free_page() -> kvm_mmu_free_shadow_page() This change makes it clear that these functions deal with shadow pages rather than struct pages. It also aligns these functions with the naming scheme for kvm_mmu_find_shadow_page() and kvm_mmu_alloc_shadow_page(). Prefer "shadow_page" over the shorter "sp" since these are core functions and the line lengths aren't terrible. No functional change intended. Reviewed-by:
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David Matlack authored
Consolidate kvm_mmu_alloc_page() and kvm_mmu_alloc_shadow_page() under the latter so that all shadow page allocation and initialization happens in one place. No functional change intended. Signed-off-by:
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David Matlack authored
Decompose kvm_mmu_get_page() into separate helper functions to increase readability and prepare for allocating shadow pages without a vcpu pointer. Specifically, pull the guts of kvm_mmu_get_page() into 2 helper functions: kvm_mmu_find_shadow_page() - Walks the page hash checking for any existing mmu pages that match the given gfn and role. kvm_mmu_alloc_shadow_page() Allocates and initializes an entirely new kvm_mmu_page. This currently requries a vcpu pointer for allocation and looking up the memslot but that will be removed in a future commit. No functional change intended. Reviewed-by:
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David Matlack authored
The quadrant is only used when gptes are 4 bytes, but mmu_alloc_{direct,shadow}_roots() pass in a non-zero quadrant for PAE page directories regardless. Make this less confusing by only passing in a non-zero quadrant when it is actually necessary. Signed-off-by: -
David Matlack authored
Instead of computing the shadow page role from scratch for every new page, derive most of the information from the parent shadow page. This eliminates the dependency on the vCPU root role to allocate shadow page tables, and reduces the number of parameters to kvm_mmu_get_page(). Preemptively split out the role calculation to a separate function for use in a following commit. Note that when calculating the MMU root role, we can take @role.passthrough, @role.direct, and @role.access directly from @vcpu->arch.mmu->root_role. Only @role.level and @role.quadrant still must be overridden for PAE page directories, when shadowing 32-bit guest page tables with PAE page tables. No functional change intended. Reviewed-by:
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David Matlack authored
The "direct" argument is vcpu->arch.mmu->root_role.direct, because unlike non-root page tables, it's impossible to have a direct root in an indirect MMU. So just use that. Suggested-by:
Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by:
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David Matlack authored
The parameter "direct" can either be true or false, and all of the callers pass in a bool variable or true/false literal, so just use the type bool. No functional change intended. Reviewed-by:
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David Matlack authored
Commit fb58a9c3 ("KVM: x86/mmu: Optimize MMU page cache lookup for fully direct MMUs") skipped the unsync checks and write flood clearing for full direct MMUs. We can extend this further to skip the checks for all direct shadow pages. Direct shadow pages in indirect MMUs (i.e. shadow paging) are used when shadowing a guest huge page with smaller pages. Such direct shadow pages, like their counterparts in fully direct MMUs, are never marked unsynced or have a non-zero write-flooding count. Checking sp->role.direct also generates better code than checking direct_map because, due to register pressure, direct_map has to get shoved onto the stack and then pulled back off. No functional change intended. Reviewed-by:
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Ben Gardon authored
In order to improve performance across multiple reads of VM stats, cache the stats metadata in the VM struct. Signed-off-by:
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Ben Gardon authored
Add an argument to the NX huge pages test to test disabling the feature on a VM using the new capability. Reviewed-by:
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Ben Gardon authored
There's currently no test coverage of NX hugepages in KVM selftests, so add a basic test to ensure that the feature works as intended. The test creates a VM with a data slot backed with huge pages. The memory in the data slot is filled with op-codes for the return instruction. The guest then executes a series of accesses on the memory, some reads, some instruction fetches. After each operation, the guest exits and the test performs some checks on the backing page counts to ensure that NX page splitting an reclaim work as expected. Reviewed-by:
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Ben Gardon authored
In some cases, the NX hugepage mitigation for iTLB multihit is not needed for all guests on a host. Allow disabling the mitigation on a per-VM basis to avoid the performance hit of NX hugepages on trusted workloads. In order to disable NX hugepages on a VM, ensure that the userspace actor has permission to reboot the system. Since disabling NX hugepages would allow a guest to crash the system, it is similar to reboot permissions. Ideally, KVM would require userspace to prove it has access to KVM's nx_huge_pages module param, e.g. so that userspace can opt out without needing full reboot permissions. But getting access to the module param file info is difficult because it is buried in layers of sysfs and module glue. Requiring CAP_SYS_BOOT is sufficient for all known use cases. Suggested-by:
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Ben Gardon authored
The braces around the KVM_CAP_XSAVE2 block also surround the KVM_CAP_PMU_CAPABILITY block, likely the result of a merge issue. Simply move the curly brace back to where it belongs. Fixes: ba7bb663 ("KVM: x86: Provide per VM capability for disabling PMU virtualization") Reviewed-by:
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Ben Gardon authored
Move the code to read the binary stats data to the KVM selftests library. It will be re-used by other tests to check KVM behavior. Also opportunistically remove an unnecessary calculation with "size_data" in stats_test. Reviewed-by:
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Sean Christopherson authored
Fix a variety of code style violations and/or inconsistencies in the binary stats test. The 80 char limit is a soft limit and can and should be ignored/violated if doing so improves the overall code readability. Specifically, provide consistent indentation and don't split expressions at arbitrary points just to honor the 80 char limit. Opportunistically expand/add comments to call out the more subtle aspects of the code. Signed-off-by:
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Ben Gardon authored
Move the code to read the binary stats descriptors to the KVM selftests library. It will be re-used by other tests to check KVM behavior. No functional change intended. Reviewed-by:
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Ben Gardon authored
Move the code to read the binary stats header to the KVM selftests library. It will be re-used by other tests to check KVM behavior. No functional change intended. Reviewed-by:
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Ben Gardon authored
There's no need to allocate dynamic memory for the stats header since its size is known at compile time. Reviewed-by:
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- 22 Jun, 2022 1 commit
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Sean Christopherson authored
Add a test to verify the "MONITOR/MWAIT never fault" quirk, and as a bonus, also verify the related "MISC_ENABLES ignores ENABLE_MWAIT" quirk. If the "never fault" quirk is enabled, MONITOR/MWAIT should always be emulated as NOPs, even if they're reported as disabled in guest CPUID. Use the MISC_ENABLES quirk to coerce KVM into toggling the MWAIT CPUID enable, as KVM now disallows manually toggling CPUID bits after running the vCPU. Signed-off-by:
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- 20 Jun, 2022 3 commits
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Sean Christopherson authored
Use exception fixup to verify VMCALL/RDMSR/WRMSR fault as expected in the Hyper-V Features test. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Explicitly do all setup at every stage of the Hyper-V Features test, e.g. set the MSR/hypercall, enable capabilities, etc... Now that the VM is recreated for every stage, values that are written into the VM's address space, i.e. shared with the guest, are reset between sub-tests, as are any capabilities, etc... Fix the hypercall params as well, which were broken in the same rework. The "hcall" struct/pointer needs to point at the hcall_params object, not the set of hypercall pages. The goofs were hidden by the test's dubious behavior of using '0' to signal "done", i.e. the MSR test ran exactly one sub-test, and the hypercall test was a gigantic nop. Fixes: 6c118643 ("KVM: selftests: Avoid KVM_SET_CPUID2 after KVM_RUN in hyperv_features test") Signed-off-by:
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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:
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