On 16.03.15 21:41, David Gibson wrote: > On Thu, Feb 05, 2015 at 01:57:11AM +0100, Alexander Graf wrote: >> >> >> On 05.02.15 01:53, David Gibson wrote: >>> On POWER, storage caching is usually configured via the MMU - attributes >>> such as cache-inhibited are stored in the TLB and the hashed page table. >>> >>> This makes correctly performing cache inhibited IO accesses awkward when >>> the MMU is turned off (real mode). Some CPU models provide special >>> registers to control the cache attributes of real mode load and stores but >>> this is not at all consistent. This is a problem in particular for SLOF, >>> the firmware used on KVM guests, which runs entirely in real mode, but >>> which needs to do IO to load the kernel. >>> >>> To simplify this qemu implements two special hypercalls, H_LOGICAL_CI_LOAD >>> and H_LOGICAL_CI_STORE which simulate a cache-inhibited load or store to >>> a logical address (aka guest physical address). SLOF uses these for IO. >>> >>> However, because these are implemented within qemu, not the host kernel, >>> these bypass any IO devices emulated within KVM itself. The simplest way >>> to see this problem is to attempt to boot a KVM guest from a virtio-blk >>> device with iothread / dataplane enabled. The iothread code relies on an >>> in kernel implementation of the virtio queue notification, which is not >>> triggered by the IO hcalls, and so the guest will stall in SLOF unable to >>> load the guest OS. >>> >>> This patch addresses this by providing in-kernel implementations of the >>> 2 hypercalls, which correctly scan the KVM IO bus. Any access to an >>> address not handled by the KVM IO bus will cause a VM exit, hitting the >>> qemu implementation as before. >>> >>> Note that a userspace change is also required, in order to enable these >>> new hcall implementations with KVM_CAP_PPC_ENABLE_HCALL. >>> >>> Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> >> >> Thanks, applied to kvm-ppc-queue. > > Any news on when this might go up to mainline? I'm aiming for 4.1. Alex -- 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
