On 2018/3/20 19:54, Peter Maydell wrote: > On 20 March 2018 at 11:36, Shannon Zhao <zhaoshengl...@huawei.com> wrote: >> >> >> On 2018/3/20 19:22, Peter Maydell wrote: >>> On 20 March 2018 at 07:26, Shannon Zhao <zhaoshengl...@huawei.com> wrote: >>>> While we skip the GIC_INTERNAL irqs, we don't change the register offset >>>> accordingly. This will overlap the GICR registers value and leave the >>>> last GIC_INTERNAL irq's registers out of update. >>>> >>>> Fix this by skipping the registers banked by GICR. >>>> >>> >>> I'm still not entirely sure what the underlying problem >>> you're trying to fix is... >>> >>> Do we fail to correctly migrate a VM without this change? >>> Does the code work on some host CPU/GIC implementations but >>> not others? Is this just improving efficiency by avoiding >>> doing some unnecessary work? >>> >> When we reboot a VM and before entering uefi or guest kernel, we expect >> all these registers staying at the initial state. But currently these >> registers of the last 32 irqs are not reset. For example, the PRIORITY >> of irq from 32 to 255 is 0 but the PRIORITY of irq from 256 to 287 is >> 0xa0(Linux kernel set the PRIORITY to 0xa0 by default). >> >> When migrating a VM, since we don't save and restore the registers of >> the last 32 irq, so the PRIORITY is 0 while we expecting 0xa0. >> And also it will overlap the PRIORITY of SGIs and PPIs. >> >> We don't fail to migrate a vm since currently we don't use the last 32 >> irqs in virt machine. But the bug is still there. > > Oh, I see, the number of registers we transfer is accounting > for the first N registers in the bank not being used, but the > first register offset to transfer wasn't. > > Can you still successfully migrate a VM from a QEMU version > without this bugfix to one with the bugfix ? > I've tested this case. I can migrate a VM between these two versions.
Thanks, -- Shannon