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authorJan Kiszka <jan.kiszka@siemens.com>2012-02-17 18:31:19 +0100
committerAvi Kivity <avi@redhat.com>2012-02-18 12:15:59 +0200
commite5ad936b0fd7dfd7fd7908be6f9f1ca88f63b96b (patch)
tree59a8f25d1499d8978945e6dbf651eb18f1332688 /hw/usb-desc.h
parent2a2af967b0bc601c9b450c72b95104e67222e5b2 (diff)
kvmvapic: Introduce TPR access optimization for Windows guests
This enables acceleration for MMIO-based TPR registers accesses of 32-bit Windows guest systems. It is mostly useful with KVM enabled, either on older Intel CPUs (without flexpriority feature, can also be manually disabled for testing) or any current AMD processor. The approach introduced here is derived from the original version of qemu-kvm. It was refactored, documented, and extended by support for user space APIC emulation, both with and without KVM acceleration. The VMState format was kept compatible, so was the ABI to the option ROM that implements the guest-side para-virtualized driver service. This enables seamless migration from qemu-kvm to upstream or, one day, between KVM and TCG mode. The basic concept goes like this: - VAPIC PV interface consisting of I/O port 0x7e and (for KVM in-kernel irqchip) a vmcall hypercall is registered - VAPIC option ROM is loaded into guest - option ROM activates TPR MMIO access reporting via port 0x7e - TPR accesses are trapped and patched in the guest to call into option ROM instead, VAPIC support is enabled - option ROM TPR helpers track state in memory and invoke hypercall to poll for pending IRQs if required Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'hw/usb-desc.h')
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