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Sean Christopherson 361209e054 KVM: Explicitly define the "memslot update in-progress" bit
KVM uses bit 0 of the memslots generation as an "update in-progress"
flag, which is used by x86 to prevent caching MMIO access while the
memslots are changing.  Although the intended behavior is flag-like,
e.g. MMIO sptes intentionally drop the in-progress bit so as to avoid
caching data from in-flux memslots, the implementation oftentimes treats
the bit as part of the generation number itself, e.g. incrementing the
generation increments twice, once to set the flag and once to clear it.

Prior to commit 4bd518f159 ("KVM: use separate generations for
each address space"), incorporating the "update in-progress" bit into
the generation number largely made sense, e.g. "real" generations are
even, "bogus" generations are odd, most code doesn't need to be aware of
the bit, etc...

Now that unique memslots generation numbers are assigned to each address
space, stealthing the in-progress status into the generation number
results in a wide variety of subtle code, e.g. kvm_create_vm() jumps
over bit 0 when initializing the memslots generation without any hint as
to why.

Explicitly define the flag and convert as much code as possible (which
isn't much) to actually treat it like a flag.  This paves the way for
eventually using a different bit for "update in-progress" so that it can
be a flag in truth instead of a awkward extension to the generation
number.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-02-20 22:48:34 +01:00
Documentation IOMMU Fix for Linux v5.0-rc5: 2019-02-08 15:34:10 -08:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
arch KVM: Explicitly define the "memslot update in-progress" bit 2019-02-20 22:48:34 +01:00
block for-linus-20190209 2019-02-09 10:26:09 -08:00
certs kbuild: remove redundant target cleaning on failure 2019-01-06 09:46:51 +09:00
crypto crypto: sm3 - fix undefined shift by >= width of value 2019-01-10 21:37:32 +08:00
drivers dmaengine-fix-5.0-rc6 2019-02-10 10:39:37 -08:00
firmware kbuild: change filechk to surround the given command with { } 2019-01-06 09:46:51 +09:00
fs for-linus-20190209 2019-02-09 10:26:09 -08:00
include KVM: Explicitly define the "memslot update in-progress" bit 2019-02-20 22:48:34 +01:00
init psi: clarify the Kconfig text for the default-disable option 2019-02-01 15:46:24 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:48:18 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 11:21:54 -08:00
mm mm: migrate: don't rely on __PageMovable() of newpage after unlocking it 2019-02-01 15:46:24 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 11:21:54 -08:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-01-30 15:24:45 +01:00
scripts Bug fixes for gcc-plugins 2019-01-21 13:07:03 +13:00
security apparmor: Fix aa_label_build() error handling for failed merges 2019-02-01 08:01:39 -08:00
sound sound fixes for 5.0-rc6 2019-02-07 08:33:56 +00:00
tools selftests: kvm: add selftest for releasing VM file descriptor while in L2 2019-02-12 13:12:12 +01:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM: Explicitly define the "memslot update in-progress" bit 2019-02-20 22:48:34 +01:00
.clang-format clang-format: Update .clang-format with the latest for_each macro list 2019-01-19 19:26:06 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap A few early MIPS fixes for 4.21: 2019-01-05 12:48:25 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Add CREDITS entry for Shaohua Li 2019-01-04 14:27:09 -07:00
Kbuild kbuild: use assignment instead of define ... endef for filechk_* rules 2019-01-06 10:22:35 +09:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2019-02-09 13:43:12 -08:00
Makefile Linux 5.0-rc6 2019-02-10 14:42:20 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.