forked from wrenn/wrenn
pptx704
c93ad5e2db
Restructure pause to: block new operations (StatusPausing), drain proxy connections with 5s grace, force-close remaining via context cancellation, drop page cache, inflate balloon, then freeze vCPUs. Previously connections could arrive during the pause window and API operations weren't blocked. Handle UFFD_EVENT_REMOVE/UNMAP/REMAP/FORK gracefully instead of crashing the UFFD server. These events fire during balloon deflation on snapshot restore, killing the page fault handler and preventing VM boot. Also adds ConnTracker.ForceClose() with cancellable context propagated through the proxy handler, so lingering proxy connections are actively terminated rather than left dangling.
93 lines
2.4 KiB
Go
93 lines
2.4 KiB
Go
// SPDX-License-Identifier: Apache-2.0
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// Modifications by M/S Omukk
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// Package uffd implements a userfaultfd-based memory server for Firecracker
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// snapshot restore. When a VM is restored from a snapshot, instead of loading
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// the entire memory file upfront, the UFFD handler intercepts page faults
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// and serves memory pages on demand from the snapshot's compact diff file.
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package uffd
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/*
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#include <sys/syscall.h>
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#include <fcntl.h>
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#include <linux/userfaultfd.h>
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#include <sys/ioctl.h>
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struct uffd_pagefault {
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__u64 flags;
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__u64 address;
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__u32 ptid;
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};
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*/
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import "C"
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import (
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"fmt"
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"syscall"
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"unsafe"
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)
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const (
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UFFD_EVENT_PAGEFAULT = C.UFFD_EVENT_PAGEFAULT
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UFFD_EVENT_FORK = C.UFFD_EVENT_FORK
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UFFD_EVENT_REMAP = C.UFFD_EVENT_REMAP
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UFFD_EVENT_REMOVE = C.UFFD_EVENT_REMOVE
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UFFD_EVENT_UNMAP = C.UFFD_EVENT_UNMAP
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UFFD_PAGEFAULT_FLAG_WRITE = C.UFFD_PAGEFAULT_FLAG_WRITE
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UFFDIO_COPY = C.UFFDIO_COPY
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UFFDIO_COPY_MODE_WP = C.UFFDIO_COPY_MODE_WP
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)
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type (
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uffdMsg = C.struct_uffd_msg
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uffdPagefault = C.struct_uffd_pagefault
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uffdioCopy = C.struct_uffdio_copy
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)
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// fd wraps a userfaultfd file descriptor received from Firecracker.
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type fd uintptr
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// copy installs a page into guest memory at the given address using UFFDIO_COPY.
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// mode controls write-protection: use UFFDIO_COPY_MODE_WP to preserve WP bit.
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func (f fd) copy(addr, pagesize uintptr, data []byte, mode C.ulonglong) error {
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alignedAddr := addr &^ (pagesize - 1)
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cpy := uffdioCopy{
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src: C.ulonglong(uintptr(unsafe.Pointer(&data[0]))),
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dst: C.ulonglong(alignedAddr),
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len: C.ulonglong(pagesize),
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mode: mode,
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copy: 0,
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}
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_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(f), UFFDIO_COPY, uintptr(unsafe.Pointer(&cpy)))
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if errno != 0 {
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return errno
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}
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if cpy.copy != C.longlong(pagesize) {
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return fmt.Errorf("UFFDIO_COPY copied %d bytes, expected %d", cpy.copy, pagesize)
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}
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return nil
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}
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// close closes the userfaultfd file descriptor.
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func (f fd) close() error {
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return syscall.Close(int(f))
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}
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// getMsgEvent extracts the event type from a uffd_msg.
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func getMsgEvent(msg *uffdMsg) C.uchar {
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return msg.event
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}
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// getMsgArg extracts the arg union from a uffd_msg.
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func getMsgArg(msg *uffdMsg) [24]byte {
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return msg.arg
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}
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// getPagefaultAddress extracts the faulting address from a uffd_pagefault.
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func getPagefaultAddress(pf *uffdPagefault) uintptr {
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return uintptr(pf.address)
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}
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