Sreenad Menon 5ad8b5afc5 devices: virtio: Always inject interrupts if hypervisor can handle ... Gunyah hypervisor supports virtio-mmio transport only in some products on which CrosVM is also used. Qualcomm has developed a wrapper program which uses CrosVM's libdevices crate. Gunyah hypervisor has some optimizations for how virtio-mmio register access are handled. Normally they are synchronous access - meaning any access of virtio-mmio register by a guest will cause a fault, which requires blocking the guest VCPU until the access can be served by CrosVM running in a different VM. Since that could induce long delays for guest (esp since the OS in which CrosVM is hosted is considered untrusted), Gunyah hypervisor caches all virtio-mmio registers in its address space. Any read access is handled without requiring intervention from CrosVM. Write access is handled asynchronously - i,e a write will cause hypervisor to updates its copy of the register, unblock the guest vcpu and simultaneously notify CrosVM about the update. By the time CrosVM gets to notice the update, guest could have progressed lot more. This works reasonably well for many devices and registers. One problem case is writes to VIRTIO_MMIO_INTERRUPT_ACK, which signals the guest having seen an interrupt. CrosVM seems to rely on synchronous handling of this register write. Any attempts to kick guest via signal method of 'struct Interrupt' (devices/src/virtio/interrupt.rs) skips sending a kick if prior kick is "not yet" acknowledged, which fails if writes to VIRTIO_MMIO_INTERRUPT_ACK is asynchronous. This patch introduces a 'async_intr_status' flag in signal method which allows the kick to be always delivered to guest independent of the status of acknowledgement of prior kicks. Hypervisor will queue kick requests and deliver another kick after current kick is processed. Its expected that only the Qualcomm wrapper program will initialize the interrupt object with 'async_intr_status' flag set and hence the upstream CrosVM should not be affected because of this change. BUG=b:243368499 Change-Id: I76568d9d8bc3be00c75c52d4a51d39410c5c35b3 Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3965686 Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>		2022-10-20 01:25:48 +00:00
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src	devices: virtio: Always inject interrupts if hypervisor can handle	2022-10-20 01:25:48 +00:00
Cargo.toml	crosvm: GPU and display arg parsing for Windows.	2022-10-18 05:17:53 +00:00