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Change to report the KVM_CAP_MAX_VCPUS extension from globally to per-VM to allow userspace to be able to query maximum vCPUs for TDX guest via checking the KVM_CAP_MAX_VCPU extension on per-VM basis. Today KVM x86 reports KVM_MAX_VCPUS as guest's maximum vCPUs for all guests globally, and userspace, i.e. Qemu, queries the KVM_MAX_VCPUS extension globally but not on per-VM basis. TDX has its own limit of maximum vCPUs it can support for all TDX guests in addition to KVM_MAX_VCPUS. TDX module reports this limit via the MAX_VCPU_PER_TD global metadata. Different modules may report different values. In practice, the reported value reflects the maximum logical CPUs that ALL the platforms that the module supports can possibly have. Note some old modules may also not support this metadata, in which case the limit is U16_MAX. The current way to always report KVM_MAX_VCPUS in the KVM_CAP_MAX_VCPUS extension is not enough for TDX. To accommodate TDX, change to report the KVM_CAP_MAX_VCPUS extension on per-VM basis. Specifically, override kvm->max_vcpus in tdx_vm_init() for TDX guest, and report kvm->max_vcpus in the KVM_CAP_MAX_VCPUS extension check. Change to report "the number of logical CPUs the platform has" as the maximum vCPUs for TDX guest. Simply forwarding the MAX_VCPU_PER_TD reported by the TDX module would result in an unpredictable ABI because the reported value to userspace would be depending on whims of TDX modules. This works in practice because of the MAX_VCPU_PER_TD reported by the TDX module will never be smaller than the one reported to userspace. But to make sure KVM never reports an unsupported value, sanity check the MAX_VCPU_PER_TD reported by TDX module is not smaller than the number of logical CPUs the platform has, otherwise refuse to use TDX. Note, when creating a TDX guest, TDX actually requires the "maximum vCPUs for _this_ TDX guest" as an input to initialize the TDX guest. But TDX guest's maximum vCPUs is not part of TDREPORT thus not part of attestation, thus there's no need to allow userspace to explicitly _configure_ the maximum vCPUs on per-VM basis. KVM will simply use kvm->max_vcpus as input when initializing the TDX guest. Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.