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Linux kernel source tree
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On AMD CPUs without ensuring cache consistency, each memory page reclamation in an SEV guest triggers a call to do WBNOINVD/WBINVD on all CPUs, thereby affecting the performance of other programs on the host. Typically, an AMD server may have 128 cores or more, while the SEV guest might only utilize 8 of these cores. Meanwhile, host can use qemu-affinity to bind these 8 vCPUs to specific physical CPUs. Therefore, keeping a record of the physical core numbers each time a vCPU runs can help avoid flushing the cache for all CPUs every time. Take care to allocate the cpumask used to track which CPUs have run a vCPU when copying or moving an "encryption context", as nothing guarantees memory in a mirror VM is a strict subset of the ASID owner, and the destination VM for intrahost migration needs to maintain it's own set of CPUs. E.g. for intrahost migration, if a CPU was used for the source VM but not the destination VM, then it can only have cached memory that was accessible to the source VM. And a CPU that was run in the source is also used by the destination is no different than a CPU that was run in the destination only. Note, KVM is guaranteed to do flush caches prior to sev_vm_destroy(), thanks to kvm_arch_guest_memory_reclaimed for SEV and SEV-ES, and kvm_arch_gmem_invalidate() for SEV-SNP. I.e. it's safe to free the cpumask prior to unregistering encrypted regions and freeing the ASID. Opportunistically clean up sev_vm_destroy()'s comment regarding what is (implicitly, what isn't) skipped for mirror VMs. Cc: Srikanth Aithal <sraithal@amd.com> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by: Zheyun Shen <szy0127@sjtu.edu.cn> Link: https://lore.kernel.org/r/20250522233733.3176144-9-seanjc@google.com Link: https://lore.kernel.org/all/935a82e3-f7ad-47d7-aaaf-f3d2b62ed768@amd.com Co-developed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> |
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
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| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .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.