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678e315e78
When lazy save/restore of MSR_KERNEL_GS_BASE was introduced[1], the MSR was intercepted in all modes and was only restored for the host when the guest is in 64-bit mode. So at the time, going through the full host restore prior to accessing MSR_KERNEL_GS_BASE was necessary to load host state and was not a significant waste of cycles. Later, MSR_KERNEL_GS_BASE interception was disabled for a 64-bit guest[2], and then unconditionally saved/restored for the host[3]. As a result, loading full host state is overkill for accesses to MSR_KERNEL_GS_BASE, and completely unnecessary when the guest is not in 64-bit mode. Add a dedicated utility to read/write the guest's MSR_KERNEL_GS_BASE (outside of the save/restore flow) to minimize the overhead incurred when accessing the MSR. When setting EFER, only decache the MSR if the new EFER will disable long mode. Removing out-of-band usage of vmx_load_host_state() also eliminates, or at least reduces, potential corner cases in its usage, which in turn will (hopefuly) make it easier to reason about future changes to the save/restore flow, e.g. optimization of saving host state. [1] commit |
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arch | ||
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certs | ||
crypto | ||
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 | ||
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 Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.