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Paolo Bonzini 6cd88243c7 KVM: x86: do not report a vCPU as preempted outside instruction boundaries
If a vCPU is outside guest mode and is scheduled out, it might be in the
process of making a memory access.  A problem occurs if another vCPU uses
the PV TLB flush feature during the period when the vCPU is scheduled
out, and a virtual address has already been translated but has not yet
been accessed, because this is equivalent to using a stale TLB entry.

To avoid this, only report a vCPU as preempted if sure that the guest
is at an instruction boundary.  A rescheduling request will be delivered
to the host physical CPU as an external interrupt, so for simplicity
consider any vmexit *not* instruction boundary except for external
interrupts.

It would in principle be okay to report the vCPU as preempted also
if it is sleeping in kvm_vcpu_block(): a TLB flush IPI will incur the
vmentry/vmexit overhead unnecessarily, and optimistic spinning is
also unlikely to succeed.  However, leave it for later because right
now kvm_vcpu_check_block() is doing memory accesses.  Even
though the TLB flush issue only applies to virtual memory address,
it's very much preferrable to be conservative.

Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2022-06-08 04:21:07 -04:00
arch KVM: x86: do not report a vCPU as preempted outside instruction boundaries 2022-06-08 04:21:07 -04:00
block Revert "block: release rq qos structures for queue without disk" 2022-05-02 10:06:40 -06:00
certs Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
crypto for-5.18/64bit-pi-2022-03-25 2022-03-26 12:01:35 -07:00
Documentation Documentation: kvm: reorder ARM-specific section about KVM_SYSTEM_EVENT_SUSPEND 2022-05-25 05:15:43 -04:00
drivers s390/uv_uapi: depend on CONFIG_S390 2022-05-25 05:11:36 -04:00
fs gfs2 fixes 2022-05-13 14:32:53 -07:00
include KVM/riscv changes for 5.19 2022-05-25 05:09:49 -04:00
init Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug 2022-04-13 13:37:47 -04:00
ipc fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
kernel entry/kvm: Exit to user mode when TIF_NOTIFY_SIGNAL is set 2022-06-07 11:19:00 -04:00
lib dim: initialize all struct fields 2022-05-09 17:20:37 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm hotfixes for 5.18-rc7 2022-05-13 10:22:37 -07:00
net NFS client bugfixes for Linux 5.18 2022-05-13 11:04:37 -07:00
samples sched/tracing: Append prev_state to tp args instead 2022-05-12 00:37:11 +02:00
scripts Merge branch kvm-arm64/hyp-stack-guard into kvmarm-master/next 2022-05-04 09:42:37 +01:00
security hardening updates for v5.18-rc1-fix1 2022-03-31 11:43:01 -07:00
sound ASoC: Fixes for v5.18 2022-05-08 10:49:25 +02:00
tools KVM: selftests: Make hyperv_clock selftest more stable 2022-06-07 11:28:50 -04:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM: Don't null dereference ops->destroy 2022-06-07 11:18:59 -04:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap hotfixes for 5.18-rc7 2022-05-13 10:22:37 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS KVM: s390: Fix and feature for 5.19 2022-05-25 05:11:21 -04:00
Makefile Linux 5.18-rc7 2022-05-15 18:08:58 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.