0caa0a77c2
Probe MSR_TSC_AUX whether or not RDTSCP is supported in the host, and if probing succeeds, load the guest's MSR_TSC_AUX into hardware prior to VMRUN. Because SVM doesn't support interception of RDPID, RDPID cannot be disallowed in the guest (without resorting to binary translation). Leaving the host's MSR_TSC_AUX in hardware would leak the host's value to the guest if RDTSCP is not supported. Note, there is also a kernel bug that prevents leaking the host's value. The host kernel initializes MSR_TSC_AUX if and only if RDTSCP is supported, even though the vDSO usage consumes MSR_TSC_AUX via RDPID. I.e. if RDTSCP is not supported, there is no host value to leak. But, if/when the host kernel bug is fixed, KVM would start leaking MSR_TSC_AUX in the case where hardware supports RDPID but RDTSCP is unavailable for whatever reason. Probing MSR_TSC_AUX will also allow consolidating the probe and define logic in common x86, and will make it simpler to condition the existence of MSR_TSX_AUX (from the guest's perspective) on RDTSCP *or* RDPID. Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20210504171734.1434054-7-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.