Maxim Levitsky fb28875fd7 KVM: x86: smm: preserve interrupt shadow in SMRAM
When #SMI is asserted, the CPU can be in interrupt shadow due to sti or
mov ss.

It is not mandatory in  Intel/AMD prm to have the #SMI blocked during the
shadow, and on top of that, since neither SVM nor VMX has true support
for SMI window, waiting for one instruction would mean single stepping
the guest.

Instead, allow #SMI in this case, but both reset the interrupt window and
stash its value in SMRAM to restore it on exit from SMM.

This fixes rare failures seen mostly on windows guests on VMX, when #SMI
falls on the sti instruction which mainfest in VM entry failure due
to EFLAGS.IF not being set, but STI interrupt window still being set
in the VMCS.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20221025124741.228045-24-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2022-11-09 12:31:26 -05:00
2022-09-28 09:02:20 +02:00
2022-09-28 09:02:20 +02:00
2022-10-20 21:27:21 -07:00
2022-09-28 09:02:20 +02:00
2022-11-06 15:07:11 -08:00

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.
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