ChangeSet 1.1576, 2005/05/28 09:53:39+01:00, arun.sharma@xxxxxxxxx
[PATCH] vmx-io.patch
Fix some of the race conditions that show up when the device models are
running on one CPU and the VMX domain is running on another on a SMP
system.
Signed-off-by: Arun Sharma <arun.sharma@xxxxxxxxx>
arch/x86/vmx.c | 3 -
arch/x86/vmx_io.c | 82 ++++++++++++++++++++++++++++-------------
arch/x86/vmx_platform.c | 3 -
include/asm-x86/vmx_platform.h | 1
4 files changed, 59 insertions(+), 30 deletions(-)
diff -Nru a/xen/arch/x86/vmx.c b/xen/arch/x86/vmx.c
--- a/xen/arch/x86/vmx.c 2005-05-28 05:03:39 -04:00
+++ b/xen/arch/x86/vmx.c 2005-05-28 05:03:39 -04:00
@@ -465,7 +465,7 @@
set_bit(ARCH_VMX_IO_WAIT, &d->arch.arch_vmx.flags);
p->state = STATE_IOREQ_READY;
evtchn_send(IOPACKET_PORT);
- do_block();
+ vmx_wait_io();
}
enum { COPY_IN = 0, COPY_OUT };
@@ -1266,7 +1266,6 @@
case EXIT_REASON_PENDING_INTERRUPT:
__vmwrite(CPU_BASED_VM_EXEC_CONTROL,
MONITOR_CPU_BASED_EXEC_CONTROLS);
- vmx_intr_assist(ed);
break;
case EXIT_REASON_TASK_SWITCH:
__vmx_bug(®s);
diff -Nru a/xen/arch/x86/vmx_io.c b/xen/arch/x86/vmx_io.c
--- a/xen/arch/x86/vmx_io.c 2005-05-28 05:03:39 -04:00
+++ b/xen/arch/x86/vmx_io.c 2005-05-28 05:03:39 -04:00
@@ -34,9 +34,6 @@
#include <asm/vmx_virpit.h>
#ifdef CONFIG_VMX
-
-extern long do_block();
-
#if defined (__i386__)
static void load_cpu_user_regs(struct cpu_user_regs *regs)
{
@@ -186,7 +183,6 @@
{
vcpu_iodata_t *vio;
ioreq_t *p;
- struct domain *d = ed->domain;
struct cpu_user_regs *regs = guest_cpu_user_regs();
unsigned long old_eax;
int sign;
@@ -196,12 +192,6 @@
mpci_p = &ed->arch.arch_vmx.vmx_platform.mpci;
inst_decoder_regs = mpci_p->inst_decoder_regs;
- /* clear the pending event */
- ed->vcpu_info->evtchn_upcall_pending = 0;
- /* clear the pending bit for port 2 */
- clear_bit(IOPACKET_PORT>>5, &ed->vcpu_info->evtchn_pending_sel);
- clear_bit(IOPACKET_PORT, &d->shared_info->evtchn_pending[0]);
-
vio = (vcpu_iodata_t *) ed->arch.arch_vmx.vmx_platform.shared_page_va;
if (vio == 0) {
VMX_DBG_LOG(DBG_LEVEL_1,
@@ -217,8 +207,8 @@
/* clear IO wait VMX flag */
if (test_bit(ARCH_VMX_IO_WAIT, &ed->arch.arch_vmx.flags)) {
if (p->state != STATE_IORESP_READY) {
- printk("got a false I/O reponse\n");
- do_block();
+ /* An interrupt send event raced us */
+ return;
} else {
p->state = STATE_INVALID;
}
@@ -282,6 +272,51 @@
}
}
+int vmx_clear_pending_io_event(struct exec_domain *ed)
+{
+ struct domain *d = ed->domain;
+
+ /* evtchn_pending is shared by other event channels in 0-31 range */
+ if (!d->shared_info->evtchn_pending[IOPACKET_PORT>>5])
+ clear_bit(IOPACKET_PORT>>5, &ed->vcpu_info->evtchn_pending_sel);
+
+ /* Note: VMX domains may need upcalls as well */
+ if (!ed->vcpu_info->evtchn_pending_sel)
+ ed->vcpu_info->evtchn_upcall_pending = 0;
+
+ /* clear the pending bit for IOPACKET_PORT */
+ return test_and_clear_bit(IOPACKET_PORT,
+ &d->shared_info->evtchn_pending[0]);
+}
+
+/* Because we've cleared the pending events first, we need to guarantee that
+ * all events to be handled by xen for VMX domains are taken care of here.
+ *
+ * interrupts are guaranteed to be checked before resuming guest.
+ * VMX upcalls have been already arranged for if necessary.
+ */
+void vmx_check_events(struct exec_domain *d)
+{
+ /* clear the event *before* checking for work. This should avoid
+ the set-and-check races */
+ if (vmx_clear_pending_io_event(current))
+ vmx_io_assist(d);
+}
+
+/* On exit from vmx_wait_io, we're guaranteed to have a I/O response from
+ the device model */
+void vmx_wait_io()
+{
+ extern void do_block();
+
+ do {
+ do_block();
+ vmx_check_events(current);
+ if (!test_bit(ARCH_VMX_IO_WAIT, ¤t->arch.arch_vmx.flags))
+ break;
+ } while(1);
+}
+
#if defined(__i386__) || defined(__x86_64__)
static inline int __fls(u32 word)
{
@@ -440,22 +475,17 @@
__vmwrite(HOST_ESP, (unsigned long)get_stack_bottom());
if (event_pending(d)) {
- if (test_bit(IOPACKET_PORT,
&d->domain->shared_info->evtchn_pending[0]))
- vmx_io_assist(d);
+ vmx_check_events(d);
- else if (test_bit(ARCH_VMX_IO_WAIT, &d->arch.arch_vmx.flags)) {
- printk("got an event while blocked on I/O\n");
- do_block();
- }
-
- /* Assumption: device model will not inject an interrupt
- * while an ioreq_t is pending i.e. the response and
- * interrupt can come together. But an interrupt without
- * a response to ioreq_t is not ok.
- */
+ if (test_bit(ARCH_VMX_IO_WAIT, &d->arch.arch_vmx.flags))
+ vmx_wait_io();
}
- if (!test_bit(ARCH_VMX_IO_WAIT, &d->arch.arch_vmx.flags))
- vmx_intr_assist(d);
+
+ /* We can't resume the guest if we're waiting on I/O */
+ ASSERT(!test_bit(ARCH_VMX_IO_WAIT, &d->arch.arch_vmx.flags));
+
+ /* We always check for interrupts before resuming guest */
+ vmx_intr_assist(d);
}
#endif /* CONFIG_VMX */
diff -Nru a/xen/arch/x86/vmx_platform.c b/xen/arch/x86/vmx_platform.c
--- a/xen/arch/x86/vmx_platform.c 2005-05-28 05:03:39 -04:00
+++ b/xen/arch/x86/vmx_platform.c 2005-05-28 05:03:39 -04:00
@@ -470,7 +470,6 @@
struct mi_per_cpu_info *mpci_p;
struct cpu_user_regs *inst_decoder_regs;
extern long evtchn_send(int lport);
- extern long do_block(void);
mpci_p = ¤t->arch.arch_vmx.vmx_platform.mpci;
inst_decoder_regs = mpci_p->inst_decoder_regs;
@@ -520,7 +519,7 @@
#endif
evtchn_send(IOPACKET_PORT);
- do_block();
+ vmx_wait_io();
}
void handle_mmio(unsigned long va, unsigned long gpa)
diff -Nru a/xen/include/asm-x86/vmx_platform.h
b/xen/include/asm-x86/vmx_platform.h
--- a/xen/include/asm-x86/vmx_platform.h 2005-05-28 05:03:39 -04:00
+++ b/xen/include/asm-x86/vmx_platform.h 2005-05-28 05:03:39 -04:00
@@ -85,6 +85,7 @@
};
extern void handle_mmio(unsigned long, unsigned long);
+extern void vmx_wait_io(void);
extern int vmx_setup_platform(struct exec_domain *, struct cpu_user_regs *);
// XXX - think about this -- maybe use bit 30 of the mfn to signify an MMIO
frame.
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