** Description changed: I am working on a project with custom inter processor interrupts (IPIs) on the RISC-V virt machine. After upgrading from version 3.1.0 to 4.1.0 which fixes a related issue (https://github.com/riscv/riscv-qemu/issues/132) I am able to use the CPU hotplug feature. However, if I try to use IPIs for communication between two cores, the wfi instruction behaves strangely. Either it does not return, or it returns on timer interrupts, even though they are disabled. The code, I use on one core to wait for an interrupt is the following. - csr_clear(sie, SIE_SEIE | SIE_STIE); - do { - wait_for_interrupt(); - sipval = csr_read(sip); - sieval = csr_read(sie); - scauseval = csr_read(scause) & 0xFF; - /* only break if wfi returns for an software interrupt */ - } while ((sipval & sieval) == 0 && scauseval != 1); - csr_set(sie, SIE_SEIE | SIE_STIE); + csr_clear(sie, SIE_SEIE | SIE_STIE); + do { + wait_for_interrupt(); + sipval = csr_read(sip); + sieval = csr_read(sie); + scauseval = csr_read(scause) & 0xFF; + /* only break if wfi returns for an software interrupt */ + } while ((sipval & sieval) == 0 && scauseval != 1); + csr_set(sie, SIE_SEIE | SIE_STIE); Since the resulting sequence does not seem to be deterministic, my guess is, that it has something to do with the communication of qemu's threads for the different cores. + + Update: + The exact same setup works fine in spike (the actual sim, not the qemu board), which might give a hint, that it is related to the interrupt controller implementation.
-- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1850378 Title: RISC-V unreliable IPIs Status in QEMU: New Bug description: I am working on a project with custom inter processor interrupts (IPIs) on the RISC-V virt machine. After upgrading from version 3.1.0 to 4.1.0 which fixes a related issue (https://github.com/riscv/riscv-qemu/issues/132) I am able to use the CPU hotplug feature. However, if I try to use IPIs for communication between two cores, the wfi instruction behaves strangely. Either it does not return, or it returns on timer interrupts, even though they are disabled. The code, I use on one core to wait for an interrupt is the following. csr_clear(sie, SIE_SEIE | SIE_STIE); do { wait_for_interrupt(); sipval = csr_read(sip); sieval = csr_read(sie); scauseval = csr_read(scause) & 0xFF; /* only break if wfi returns for an software interrupt */ } while ((sipval & sieval) == 0 && scauseval != 1); csr_set(sie, SIE_SEIE | SIE_STIE); Since the resulting sequence does not seem to be deterministic, my guess is, that it has something to do with the communication of qemu's threads for the different cores. Update: The exact same setup works fine in spike (the actual sim, not the qemu board), which might give a hint, that it is related to the interrupt controller implementation. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1850378/+subscriptions
