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authorpd <pd@cvs.openbsd.org>2020-06-28 16:52:46 +0000
committerpd <pd@cvs.openbsd.org>2020-06-28 16:52:46 +0000
commit25e11d3465eacea854fb5a6a748931d53ccd10dd (patch)
treeadd2f22f6a45c6105595b2cc40478eccbef1bc5e /usr.sbin
parentf82eff1fc0c703b464502c887036a4207aa13621 (diff)
vmd(8): Eliminate libevent state corruption
libevent functions for com, pic and rtc are now only called on event_thread. vcpu exit handlers send messages on a dev pipe and callbacks on these events do the event management (event_add, evtimer_add, etc). Previously, libevent state was mutated by two threads, event_thread, that runs all the callbacks and the vcpu thread when running exit handlers. This could have lead to libevent state corruption. Patch from Dave Voutila <dave@sisu.io> ok claudio@ tested by abieber@ and brynet@
Diffstat (limited to 'usr.sbin')
-rw-r--r--usr.sbin/vmd/i8253.c37
-rw-r--r--usr.sbin/vmd/mc146818.c32
-rw-r--r--usr.sbin/vmd/ns8250.c58
-rw-r--r--usr.sbin/vmd/vm.c72
-rw-r--r--usr.sbin/vmd/vmd.h20
5 files changed, 203 insertions, 16 deletions
diff --git a/usr.sbin/vmd/i8253.c b/usr.sbin/vmd/i8253.c
index 4cc5bc01819..b5a6bc5ff97 100644
--- a/usr.sbin/vmd/i8253.c
+++ b/usr.sbin/vmd/i8253.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: i8253.c,v 1.31 2019/11/30 00:51:29 mlarkin Exp $ */
+/* $OpenBSD: i8253.c,v 1.32 2020/06/28 16:52:45 pd Exp $ */
/*
* Copyright (c) 2016 Mike Larkin <mlarkin@openbsd.org>
*
@@ -30,6 +30,7 @@
#include "i8253.h"
#include "proc.h"
+#include "vmd.h"
#include "vmm.h"
#include "atomicio.h"
@@ -43,6 +44,35 @@ extern char *__progname;
*/
struct i8253_channel i8253_channel[3];
+static struct vm_dev_pipe dev_pipe;
+
+/*
+ * i8253_pipe_dispatch
+ *
+ * Reads a message off the pipe, expecting one that corresponds to a
+ * reset request for a specific channel.
+ */
+static void
+i8253_pipe_dispatch(int fd, short event, void *arg)
+{
+ enum pipe_msg_type msg;
+
+ msg = vm_pipe_recv(&dev_pipe);
+ switch (msg) {
+ case I8253_RESET_CHAN_0:
+ i8253_reset(0);
+ break;
+ case I8253_RESET_CHAN_1:
+ i8253_reset(1);
+ break;
+ case I8253_RESET_CHAN_2:
+ i8253_reset(2);
+ break;
+ default:
+ fatalx("%s: unexpected pipe message %d", __func__, msg);
+ }
+}
+
/*
* i8253_init
*
@@ -77,6 +107,9 @@ i8253_init(uint32_t vm_id)
evtimer_set(&i8253_channel[0].timer, i8253_fire, &i8253_channel[0]);
evtimer_set(&i8253_channel[1].timer, i8253_fire, &i8253_channel[1]);
evtimer_set(&i8253_channel[2].timer, i8253_fire, &i8253_channel[2]);
+
+ vm_pipe_init(&dev_pipe, i8253_pipe_dispatch);
+ event_add(&dev_pipe.read_ev, NULL);
}
/*
@@ -271,7 +304,7 @@ vcpu_exit_i8253(struct vm_run_params *vrp)
sel, i8253_channel[sel].mode,
i8253_channel[sel].start);
- i8253_reset(sel);
+ vm_pipe_send(&dev_pipe, sel);
}
} else {
if (i8253_channel[sel].rbs) {
diff --git a/usr.sbin/vmd/mc146818.c b/usr.sbin/vmd/mc146818.c
index 8526e20f4d6..7925bd9c459 100644
--- a/usr.sbin/vmd/mc146818.c
+++ b/usr.sbin/vmd/mc146818.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mc146818.c,v 1.21 2019/11/30 00:51:29 mlarkin Exp $ */
+/* $OpenBSD: mc146818.c,v 1.22 2020/06/28 16:52:45 pd Exp $ */
/*
* Copyright (c) 2016 Mike Larkin <mlarkin@openbsd.org>
*
@@ -63,6 +63,29 @@ struct mc146818 {
struct mc146818 rtc;
+static struct vm_dev_pipe dev_pipe;
+
+static void rtc_reschedule_per(void);
+
+/*
+ * mc146818_pipe_dispatch
+ *
+ * Reads a message off the pipe, expecting a request to reschedule periodic
+ * interrupt rate.
+ */
+static void
+mc146818_pipe_dispatch(int fd, short event, void *arg)
+{
+ enum pipe_msg_type msg;
+
+ msg = vm_pipe_recv(&dev_pipe);
+ if (msg == MC146818_RESCHEDULE_PER) {
+ rtc_reschedule_per();
+ } else {
+ fatalx("%s: unexpected pipe message %d", __func__, msg);
+ }
+}
+
/*
* rtc_updateregs
*
@@ -175,6 +198,9 @@ mc146818_init(uint32_t vm_id, uint64_t memlo, uint64_t memhi)
evtimer_add(&rtc.sec, &rtc.sec_tv);
evtimer_set(&rtc.per, rtc_fireper, (void *)(intptr_t)rtc.vm_id);
+
+ vm_pipe_init(&dev_pipe, mc146818_pipe_dispatch);
+ event_add(&dev_pipe.read_ev, NULL);
}
/*
@@ -217,7 +243,7 @@ rtc_update_rega(uint32_t data)
rtc.regs[MC_REGA] = data;
if ((rtc.regs[MC_REGA] ^ data) & 0x0f)
- rtc_reschedule_per();
+ vm_pipe_send(&dev_pipe, MC146818_RESCHEDULE_PER);
}
/*
@@ -240,7 +266,7 @@ rtc_update_regb(uint32_t data)
rtc.regs[MC_REGB] = data;
if (data & MC_REGB_PIE)
- rtc_reschedule_per();
+ vm_pipe_send(&dev_pipe, MC146818_RESCHEDULE_PER);
}
/*
diff --git a/usr.sbin/vmd/ns8250.c b/usr.sbin/vmd/ns8250.c
index 5d36cbeaaa7..a1bc492b44b 100644
--- a/usr.sbin/vmd/ns8250.c
+++ b/usr.sbin/vmd/ns8250.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ns8250.c,v 1.28 2020/06/21 20:36:07 pd Exp $ */
+/* $OpenBSD: ns8250.c,v 1.29 2020/06/28 16:52:45 pd Exp $ */
/*
* Copyright (c) 2016 Mike Larkin <mlarkin@openbsd.org>
*
@@ -37,8 +37,40 @@
extern char *__progname;
struct ns8250_dev com1_dev;
+/* Flags to distinguish calling threads to com_rcv */
+#define NS8250_DEV_THREAD 0
+#define NS8250_CPU_THREAD 1
+
+static struct vm_dev_pipe dev_pipe;
+
static void com_rcv_event(int, short, void *);
-static void com_rcv(struct ns8250_dev *, uint32_t, uint32_t);
+static void com_rcv(struct ns8250_dev *, uint32_t, uint32_t, int);
+
+/*
+ * ns8250_pipe_dispatch
+ *
+ * Reads a message off the pipe, expecting a reguest to reset events after a
+ * zero-byte read from the com device.
+ */
+static void
+ns8250_pipe_dispatch(int fd, short event, void *arg)
+{
+ enum pipe_msg_type msg;
+
+ msg = vm_pipe_recv(&dev_pipe);
+ switch(msg) {
+ case NS8250_ZERO_READ:
+ log_debug("%s: resetting events after zero byte read", __func__);
+ event_del(&com1_dev.event);
+ event_add(&com1_dev.wake, NULL);
+ break;
+ case NS8250_RATELIMIT:
+ evtimer_add(&com1_dev.rate, &com1_dev.rate_tv);
+ break;
+ default:
+ fatalx("%s: unexpected pipe message %d", __func__, msg);
+ }
+}
/*
* ratelimit
@@ -75,6 +107,7 @@ ns8250_init(int fd, uint32_t vmid)
errno = ret;
fatal("could not initialize com1 mutex");
}
+
com1_dev.fd = fd;
com1_dev.irq = 4;
com1_dev.portid = NS8250_COM1;
@@ -115,6 +148,9 @@ ns8250_init(int fd, uint32_t vmid)
timerclear(&com1_dev.rate_tv);
com1_dev.rate_tv.tv_usec = 10000;
evtimer_set(&com1_dev.rate, ratelimit, NULL);
+
+ vm_pipe_init(&dev_pipe, ns8250_pipe_dispatch);
+ event_add(&dev_pipe.read_ev, NULL);
}
static void
@@ -137,7 +173,7 @@ com_rcv_event(int fd, short kind, void *arg)
if (com1_dev.regs.lsr & LSR_RXRDY)
com1_dev.rcv_pending = 1;
else
- com_rcv(&com1_dev, (uintptr_t)arg, 0);
+ com_rcv(&com1_dev, (uintptr_t)arg, 0, NS8250_DEV_THREAD);
}
/* If pending interrupt, inject */
@@ -181,7 +217,7 @@ com_rcv_handle_break(struct ns8250_dev *com, uint8_t cmd)
* Must be called with the mutex of the com device acquired
*/
static void
-com_rcv(struct ns8250_dev *com, uint32_t vm_id, uint32_t vcpu_id)
+com_rcv(struct ns8250_dev *com, uint32_t vm_id, uint32_t vcpu_id, int thread)
{
char buf[2];
ssize_t sz;
@@ -201,8 +237,13 @@ com_rcv(struct ns8250_dev *com, uint32_t vm_id, uint32_t vcpu_id)
if (errno != EAGAIN)
log_warn("unexpected read error on com device");
} else if (sz == 0) {
- event_del(&com->event);
- event_add(&com->wake, NULL);
+ if (thread == NS8250_DEV_THREAD) {
+ event_del(&com->event);
+ event_add(&com->wake, NULL);
+ } else {
+ /* Called by vcpu thread, use pipe for event changes */
+ vm_pipe_send(&dev_pipe, NS8250_ZERO_READ);
+ }
return;
} else if (sz != 1 && sz != 2)
log_warnx("unexpected read return value %zd on com device", sz);
@@ -258,8 +299,7 @@ vcpu_process_com_data(struct vm_exit *vei, uint32_t vm_id, uint32_t vcpu_id)
/* Limit output rate if needed */
if (com1_dev.pause_ct > 0 &&
com1_dev.byte_out % com1_dev.pause_ct == 0) {
- evtimer_add(&com1_dev.rate,
- &com1_dev.rate_tv);
+ vm_pipe_send(&dev_pipe, NS8250_RATELIMIT);
} else {
/* Set TXRDY and clear "no pending interrupt" */
com1_dev.regs.iir |= IIR_TXRDY;
@@ -300,7 +340,7 @@ vcpu_process_com_data(struct vm_exit *vei, uint32_t vm_id, uint32_t vcpu_id)
com1_dev.regs.iir = 0x1;
if (com1_dev.rcv_pending)
- com_rcv(&com1_dev, vm_id, vcpu_id);
+ com_rcv(&com1_dev, vm_id, vcpu_id, NS8250_CPU_THREAD);
}
/* If pending interrupt, make sure it gets injected */
diff --git a/usr.sbin/vmd/vm.c b/usr.sbin/vmd/vm.c
index 854cc9d32ff..a9fcce4fac4 100644
--- a/usr.sbin/vmd/vm.c
+++ b/usr.sbin/vmd/vm.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: vm.c,v 1.57 2020/04/30 03:50:53 pd Exp $ */
+/* $OpenBSD: vm.c,v 1.58 2020/06/28 16:52:45 pd Exp $ */
/*
* Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -2243,3 +2243,73 @@ translate_gva(struct vm_exit* exit, uint64_t va, uint64_t* pa, int mode)
return (0);
}
+
+/*
+ * vm_pipe_init
+ *
+ * Initialize a vm_dev_pipe, setting up its file descriptors and its
+ * event structure with the given callback.
+ *
+ * Parameters:
+ * p: pointer to vm_dev_pipe struct to initizlize
+ * cb: callback to use for READ events on the read end of the pipe
+ */
+void
+vm_pipe_init(struct vm_dev_pipe *p, void (*cb)(int, short, void *))
+{
+ int ret;
+ int fds[2];
+
+ memset(p, 0, sizeof(struct vm_dev_pipe));
+
+ ret = pipe(fds);
+ if (ret)
+ fatal("failed to create vm_dev_pipe pipe");
+
+ p->read = fds[0];
+ p->write = fds[1];
+
+ event_set(&p->read_ev, p->read, EV_READ | EV_PERSIST, cb, NULL);
+}
+
+/*
+ * vm_pipe_send
+ *
+ * Send a message to an emulated device vie the provided vm_dev_pipe.
+ *
+ * Parameters:
+ * p: pointer to initialized vm_dev_pipe
+ * msg: message to send in the channel
+ */
+void
+vm_pipe_send(struct vm_dev_pipe *p, enum pipe_msg_type msg)
+{
+ size_t n;
+ n = write(p->write, &msg, sizeof(msg));
+ if (n != sizeof(msg))
+ fatal("failed to write to device pipe");
+}
+
+/*
+ * vm_pipe_recv
+ *
+ * Receive a message for an emulated device via the provided vm_dev_pipe.
+ * Returns the message value, otherwise will exit on failure.
+ *
+ * Parameters:
+ * p: pointer to initialized vm_dev_pipe
+ *
+ * Return values:
+ * a value of enum pipe_msg_type or fatal exit on read(2) error
+ */
+enum pipe_msg_type
+vm_pipe_recv(struct vm_dev_pipe *p)
+{
+ size_t n;
+ enum pipe_msg_type msg;
+ n = read(p->read, &msg, sizeof(msg));
+ if (n != sizeof(msg))
+ fatal("failed to read from device pipe");
+
+ return msg;
+}
diff --git a/usr.sbin/vmd/vmd.h b/usr.sbin/vmd/vmd.h
index d7efb329e53..8c77025f6dc 100644
--- a/usr.sbin/vmd/vmd.h
+++ b/usr.sbin/vmd/vmd.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: vmd.h,v 1.98 2019/12/12 03:53:38 pd Exp $ */
+/* $OpenBSD: vmd.h,v 1.99 2020/06/28 16:52:45 pd Exp $ */
/*
* Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -354,6 +354,21 @@ struct vmd {
int vmd_ptmfd;
};
+struct vm_dev_pipe {
+ int read;
+ int write;
+ struct event read_ev;
+};
+
+enum pipe_msg_type {
+ I8253_RESET_CHAN_0 = 0,
+ I8253_RESET_CHAN_1 = 1,
+ I8253_RESET_CHAN_2 = 2,
+ NS8250_ZERO_READ,
+ NS8250_RATELIMIT,
+ MC146818_RESCHEDULE_PER
+};
+
static inline struct sockaddr_in *
ss2sin(struct sockaddr_storage *ss)
{
@@ -442,6 +457,9 @@ int vmm_pipe(struct vmd_vm *, int, void (*)(int, short, void *));
/* vm.c */
int start_vm(struct vmd_vm *, int);
__dead void vm_shutdown(unsigned int);
+void vm_pipe_init(struct vm_dev_pipe *, void (*)(int, short, void *));
+void vm_pipe_send(struct vm_dev_pipe *, enum pipe_msg_type);
+enum pipe_msg_type vm_pipe_recv(struct vm_dev_pipe *);
/* control.c */
int config_init(struct vmd *);