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On a POWER9 system, it is possible for an interrupt to become pending for a VCPU when that VCPU is about to cede (execute a H_CEDE hypercall) and has already disabled interrupts, or in the H_CEDE processing up to the point where the XIVE context is pulled from the hardware. In such a case, the H_CEDE should not sleep, but should return immediately to the guest. However, the conditions tested in kvmppc_vcpu_woken() don't include the condition that a XIVE interrupt is pending, so the VCPU could sleep until the next decrementer interrupt. To fix this, we add a new xive_interrupt_pending() helper which looks in the XIVE context that was pulled from the hardware to see if the priority of any pending interrupt is higher (numerically lower than) the CPU priority. If so then kvmppc_vcpu_woken() will return true. If the XIVE context has never been used, then both the pipr and the cppr fields will be zero and the test will indicate that no interrupt is pending. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
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.