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A mirror of the official Linux kernel repository just in case
5a8781607e
Currently, host_rsp is cached on a per-vCPU basis, i.e. it's stored in struct vcpu_vmx. In non-nested usage the caching is for all intents and purposes 100% effective, e.g. only the first VMLAUNCH needs to synchronize VMCS.HOST_RSP since the call stack to vmx_vcpu_run() is identical each and every time. But when running a nested guest, KVM must invalidate the cache when switching the current VMCS as it can't guarantee the new VMCS has the same HOST_RSP as the previous VMCS. In other words, the cache loses almost all of its efficacy when running a nested VM. Move host_rsp to struct vmcs_host_state, which is per-VMCS, so that it is cached on a per-VMCS basis and restores its 100% hit rate when nested VMs are in play. Note that the host_rsp cache for vmcs02 essentially "breaks" when nested early checks are enabled as nested_vmx_check_vmentry_hw() will see a different RSP at the time of its VM-Enter. While it's possible to avoid even that VMCS.HOST_RSP synchronization, e.g. by employing a dedicated VM-Exit stack, there is little motivation for doing so as the overhead of two VMWRITEs (~55 cycles) is dwarfed by the overhead of the extra VMX transition (600+ cycles) and is a proverbial drop in the ocean relative to the total cost of a nested transtion (10s of thousands of cycles). Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Jim Mattson <jmattson@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| 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 Restructured Text 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.