On 08/07/2012 04:32 AM, David Gibson wrote: > On Tue, Aug 07, 2012 at 06:57:57AM +1000, Benjamin Herrenschmidt wrote: >> On Mon, 2012-08-06 at 13:13 +1000, David Gibson wrote: >> > So, I'm still trying to nut out the implications for H_CEDE, and think >> > if there are any other hypercalls that might want to block the guest >> > for a time. We were considering blocking H_PUT_TCE if qemu devices >> > had active dma maps on the previously mapped iovas. I'm not sure if >> > the discussions that led to the inclusion of the qemu IOMMU code >> > decided that was wholly unnnecessary or just not necessary for the >> > time being. >> >> For "sleeping hcalls" they will simply have to set exit_request to >> complete the hcall from the kernel perspective, leaving us in a state >> where the kernel is about to restart at srr0 + 4, along with some other >> flag (stop or halt) to actually freeze the vcpu. >> >> If such an "async" hcall decides to return an error, it can then set >> gpr3 directly using ioctls before restarting the vcpu. > > Yeah, I'd pretty much convinced myself of that by the end of > yesterday. I hope to send patches implementing these fixes today. > > There are also some questions about why our in-kernel H_CEDE works > kind of differently from x86's hlt instruction implementation (which > comes out to qemu unless the irqchip is in-kernel as well). I don't > think we have an urgent problem there though. It's the other way round, hlt sleeps in the kernel unless the irqchip is not in the kernel. Meaning the normal state of things is to sleep in the kernel (whether or not you have an emulated interrupt controller in the kernel -- the term irqchip in kernel is overloaded for x86). -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
