Author: neel
Date: Sun Oct 26 03:03:41 2014
New Revision: 273666
URL: https://svnweb.freebsd.org/changeset/base/273666
Log:
Don't pass the 'error' return from an I/O port handler directly to vm_run().
Most I/O port handlers return -1 to signal an error. If this value is returned
without modification to vm_run() then it leads to incorrect behavior because
'-1' is interpreted as ERESTART at the system call level.
Fix this by always returning EIO to signal an error from an I/O port handler.
MFC after: 1 week
Modified:
head/sys/amd64/vmm/vmm_ioport.c
Modified: head/sys/amd64/vmm/vmm_ioport.c
==============================================================================
--- head/sys/amd64/vmm/vmm_ioport.c Sun Oct 26 02:53:23 2014
(r273665)
+++ head/sys/amd64/vmm/vmm_ioport.c Sun Oct 26 03:03:41 2014
(r273666)
@@ -106,15 +106,14 @@ emulate_inout_port(struct vm *vm, int vc
uint32_t mask, val;
int error;
- error = 0;
- *retu = true;
-
- if (vmexit->u.inout.port >= MAX_IOPORTS)
- goto done;
-
- handler = ioport_handler[vmexit->u.inout.port];
- if (handler == NULL)
- goto done;
+ /*
+ * If there is no handler for the I/O port then punt to userspace.
+ */
+ if (vmexit->u.inout.port >= MAX_IOPORTS ||
+ (handler = ioport_handler[vmexit->u.inout.port]) == NULL) {
+ *retu = true;
+ return (0);
+ }
mask = vie_size2mask(vmexit->u.inout.bytes);
@@ -124,20 +123,27 @@ emulate_inout_port(struct vm *vm, int vc
error = (*handler)(vm, vcpuid, vmexit->u.inout.in,
vmexit->u.inout.port, vmexit->u.inout.bytes, &val);
+ if (error) {
+ /*
+ * The value returned by this function is also the return value
+ * of vm_run(). This needs to be a positive number otherwise it
+ * can be interpreted as a "pseudo-error" like ERESTART.
+ *
+ * Enforce this by mapping all errors to EIO.
+ */
+ return (EIO);
+ }
- if (!error) {
- *retu = false;
- if (vmexit->u.inout.in) {
- vmexit->u.inout.eax &= ~mask;
- vmexit->u.inout.eax |= val & mask;
- error = vm_set_register(vm, vcpuid,
- VM_REG_GUEST_RAX, vmexit->u.inout.eax);
- KASSERT(error == 0, ("emulate_ioport: error %d "
- "setting guest rax register", error));
- }
+ if (vmexit->u.inout.in) {
+ vmexit->u.inout.eax &= ~mask;
+ vmexit->u.inout.eax |= val & mask;
+ error = vm_set_register(vm, vcpuid, VM_REG_GUEST_RAX,
+ vmexit->u.inout.eax);
+ KASSERT(error == 0, ("emulate_ioport: error %d setting guest "
+ "rax register", error));
}
-done:
- return (error);
+ *retu = false;
+ return (0);
}
static int
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