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On POWER9 DD2.1 and below, sometimes on a Hypervisor Data Storage Interrupt (HDSI) the HDSISR is not be updated at all. To work around this we put a canary value into the HDSISR before returning to a guest and then check for this canary when we take a HDSI. If we find the canary on a HDSI, we know the hardware didn't update the HDSISR. In this case we return to the guest to retake the HDSI which should correctly update the HDSISR the second time HDSI entry. After talking to Paulus we've applied this workaround to all POWER9 CPUs. The workaround of returning to the guest shouldn't ever be triggered on well behaving CPU. The extra instructions should have negligible performance impact. Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.