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1ed0f119c5
Explicitly invalidate posted_intr_nv when emulating nested VM-Enter and posted interrupts are disabled to make it clear that posted_intr_nv is valid if and only if nested posted interrupts are enabled, and as a cheap way to harden against KVM bugs. KVM initializes posted_intr_nv to -1 at vCPU creation and resets it to -1 when unloading vmcs12 and/or leaving nested mode, i.e. this is not a bug fix (or at least, it's not intended to be a bug fix). Note, tracking nested.posted_intr_nv as a u16 subtly adds a measure of safety, as it prevents unintentionally matching KVM's informal "no IRQ" vector of -1, stored as a signed int. Because a u16 can be always be represented as a signed int, the effective "invalid" value of posted_intr_nv, 65535, will be preserved as-is when comparing against an int, i.e. will be zero-extended, not sign-extended, and thus won't get a false positive if KVM is buggy and compares posted_intr_nv against -1. Opportunistically add a comment in vmx_deliver_nested_posted_interrupt() to call out that it must check vmx->nested.posted_intr_nv, not the vector in vmcs12, which is presumably the _entire_ reason nested.posted_intr_nv exists. E.g. vmcs12 is a KVM-controlled snapshot, so there are no TOCTOU races to worry about, the only potential badness is if the vCPU leaves nested and frees vmcs12 between the sender checking is_guest_mode() and dereferencing the vmcs12 pointer. Link: https://lore.kernel.org/r/20240906043413.1049633-7-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> |
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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 reStructuredText 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.