svn commit: r269043 - head/usr.sbin/bhyve
Neel Natu
neel at FreeBSD.org
Thu Jul 24 05:31:57 UTC 2014
Author: neel
Date: Thu Jul 24 05:31:57 2014
New Revision: 269043
URL: http://svnweb.freebsd.org/changeset/base/269043
Log:
Reduce the proliferation of VMEXIT_RESTART in task_switch.c.
This is in preparation for further simplification of the return values from
VM exit handlers in bhyve(8).
Modified:
head/usr.sbin/bhyve/task_switch.c
Modified: head/usr.sbin/bhyve/task_switch.c
==============================================================================
--- head/usr.sbin/bhyve/task_switch.c Thu Jul 24 01:38:11 2014 (r269042)
+++ head/usr.sbin/bhyve/task_switch.c Thu Jul 24 05:31:57 2014 (r269043)
@@ -48,15 +48,6 @@ __FBSDID("$FreeBSD$");
#include "bhyverun.h"
/*
- * Various functions in this file use 0 to denote success and VMEXIT_ABORT
- * or VMEXIT_RESTART to denote failure. This assumes that the VMEXIT_xyz
- * macros expand to non-zero values. Enforce this with a compile-time
- * assertion.
- */
-CTASSERT(VMEXIT_ABORT != 0);
-CTASSERT(VMEXIT_RESTART != 0);
-
-/*
* Using 'struct i386tss' is tempting but causes myriad sign extension
* issues because all of its fields are defined as signed integers.
*/
@@ -175,6 +166,10 @@ sel_exception(struct vmctx *ctx, int vcp
vm_inject_fault(ctx, vcpu, vector, 1, sel);
}
+/*
+ * Return 0 if the selector 'sel' in within the limits of the GDT/LDT
+ * and non-zero otherwise.
+ */
static int
desc_table_limit_check(struct vmctx *ctx, int vcpu, uint16_t sel)
{
@@ -197,6 +192,14 @@ desc_table_limit_check(struct vmctx *ctx
return (0);
}
+/*
+ * Read/write the segment descriptor 'desc' into the GDT/LDT slot referenced
+ * by the selector 'sel'.
+ *
+ * Returns 0 on success.
+ * Returns 1 if an exception was injected into the guest.
+ * Returns -1 otherwise.
+ */
static int
desc_table_rw(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging,
uint16_t sel, struct user_segment_descriptor *desc, bool doread)
@@ -236,6 +239,13 @@ desc_table_write(struct vmctx *ctx, int
return (desc_table_rw(ctx, vcpu, paging, sel, desc, false));
}
+/*
+ * Read the TSS descriptor referenced by 'sel' into 'desc'.
+ *
+ * Returns 0 on success.
+ * Returns 1 if an exception was injected into the guest.
+ * Returns -1 otherwise.
+ */
static int
read_tss_descriptor(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
uint16_t sel, struct user_segment_descriptor *desc)
@@ -252,18 +262,13 @@ read_tss_descriptor(struct vmctx *ctx, i
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
else
sel_exception(ctx, vcpu, IDT_GP, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
sup_paging = ts->paging;
sup_paging.cpl = 0; /* implicit supervisor mode */
error = desc_table_read(ctx, vcpu, &sup_paging, sel, desc);
- if (error < 0)
- return (VMEXIT_ABORT);
- else if (error > 0)
- return (VMEXIT_RESTART);
- else
- return (0);
+ return (error);
}
static bool
@@ -294,6 +299,13 @@ ldt_desc(int sd_type)
return (sd_type == SDT_SYSLDT);
}
+/*
+ * Validate the descriptor 'seg_desc' associated with 'segment'.
+ *
+ * Returns 0 on success.
+ * Returns 1 if an exception was injected into the guest.
+ * Returns -1 otherwise.
+ */
static int
validate_seg_desc(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
int segment, struct seg_desc *seg_desc)
@@ -332,13 +344,13 @@ validate_seg_desc(struct vmctx *ctx, int
/* LDT selector must point into the GDT */
if (ldtseg && ISLDT(sel)) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
/* Descriptor table limit check */
if (desc_table_limit_check(ctx, vcpu, sel)) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
/* NULL selector */
@@ -346,7 +358,7 @@ validate_seg_desc(struct vmctx *ctx, int
/* Code and stack segment selectors cannot be NULL */
if (codeseg || stackseg) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
seg_desc->base = 0;
seg_desc->limit = 0;
@@ -358,10 +370,8 @@ validate_seg_desc(struct vmctx *ctx, int
sup_paging = ts->paging;
sup_paging.cpl = 0; /* implicit supervisor mode */
error = desc_table_read(ctx, vcpu, &sup_paging, sel, &usd);
- if (error < 0)
- return (VMEXIT_ABORT);
- else if (error > 0)
- return (VMEXIT_RESTART);
+ if (error)
+ return (error);
/* Verify that the descriptor type is compatible with the segment */
if ((ldtseg && !ldt_desc(usd.sd_type)) ||
@@ -369,7 +379,7 @@ validate_seg_desc(struct vmctx *ctx, int
(dataseg && !data_desc(usd.sd_type)) ||
(stackseg && !stack_desc(usd.sd_type))) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
/* Segment must be marked present */
@@ -381,7 +391,7 @@ validate_seg_desc(struct vmctx *ctx, int
else
idtvec = IDT_NP;
sel_exception(ctx, vcpu, idtvec, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
cs = GETREG(ctx, vcpu, VM_REG_GUEST_CS);
@@ -391,7 +401,7 @@ validate_seg_desc(struct vmctx *ctx, int
if (stackseg && (rpl != cpl || dpl != cpl)) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
if (codeseg) {
@@ -399,7 +409,7 @@ validate_seg_desc(struct vmctx *ctx, int
if ((conforming && (cpl < dpl)) ||
(!conforming && (cpl != dpl))) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
}
@@ -415,7 +425,7 @@ validate_seg_desc(struct vmctx *ctx, int
if (!conforming && (rpl > dpl || cpl > dpl)) {
sel_exception(ctx, vcpu, IDT_TS, sel, ts->ext);
- return (VMEXIT_RESTART);
+ return (1);
}
}
*seg_desc = usd_to_seg_desc(&usd);
@@ -464,6 +474,13 @@ update_seg_desc(struct vmctx *ctx, int v
assert(error == 0);
}
+/*
+ * Update the vcpu registers to reflect the state of the new task.
+ *
+ * Returns 0 on success.
+ * Returns 1 if an exception was injected into the guest.
+ * Returns -1 otherwise.
+ */
static int
tss32_restore(struct vmctx *ctx, int vcpu, struct vm_task_switch *ts,
uint16_t ot_sel, struct tss32 *tss, struct iovec *iov)
@@ -506,7 +523,7 @@ tss32_restore(struct vmctx *ctx, int vcp
reserved = ~maxphyaddr | 0x1E6;
if (pdpte[i] & reserved) {
vm_inject_gp(ctx, vcpu);
- return (VMEXIT_RESTART);
+ return (1);
}
}
SETREG(ctx, vcpu, VM_REG_GUEST_PDPTE0, pdpte[0]);
@@ -595,6 +612,15 @@ tss32_restore(struct vmctx *ctx, int vcp
return (0);
}
+/*
+ * Push an error code on the stack of the new task. This is needed if the
+ * task switch was triggered by a hardware exception that causes an error
+ * code to be saved (e.g. #PF).
+ *
+ * Returns 0 on success.
+ * Returns 1 if an exception was injected into the guest.
+ * Returns -1 otherwise.
+ */
static int
push_errcode(struct vmctx *ctx, int vcpu, struct vm_guest_paging *paging,
int task_type, uint32_t errcode)
@@ -640,26 +666,40 @@ push_errcode(struct vmctx *ctx, int vcpu
if (vie_calculate_gla(paging->cpu_mode, VM_REG_GUEST_SS,
&seg_desc, esp, bytes, stacksize, PROT_WRITE, &gla)) {
sel_exception(ctx, vcpu, IDT_SS, stacksel, 1);
- return (VMEXIT_RESTART);
+ return (1);
}
if (vie_alignment_check(paging->cpl, bytes, cr0, rflags, gla)) {
vm_inject_ac(ctx, vcpu, 1);
- return (VMEXIT_RESTART);
+ return (1);
}
error = vm_copy_setup(ctx, vcpu, paging, gla, bytes, PROT_WRITE,
iov, nitems(iov));
- assert(error == 0 || error == 1 || error == -1);
- if (error) {
- return ((error == 1) ? VMEXIT_RESTART : VMEXIT_ABORT);
- }
+ if (error)
+ return (error);
vm_copyout(ctx, vcpu, &errcode, iov, bytes);
SETREG(ctx, vcpu, VM_REG_GUEST_RSP, esp);
return (0);
}
+/*
+ * Evaluate return value from helper functions and potentially return to
+ * the VM run loop.
+ * 0: success
+ * +1: an exception was injected into the guest vcpu
+ * -1: unrecoverable/programming error
+ */
+#define CHKERR(x) \
+ do { \
+ assert(((x) == 0) || ((x) == 1) || ((x) == -1)); \
+ if ((x) == -1) \
+ return (VMEXIT_ABORT); \
+ else if ((x) == 1) \
+ return (VMEXIT_CONTINUE); \
+ } while (0)
+
int
vmexit_task_switch(struct vmctx *ctx, struct vm_exit *vmexit, int *pvcpu)
{
@@ -695,8 +735,7 @@ vmexit_task_switch(struct vmctx *ctx, st
/* Fetch the new TSS descriptor */
error = read_tss_descriptor(ctx, vcpu, task_switch, nt_sel, &nt_desc);
- if (error)
- return (error);
+ CHKERR(error);
nt = usd_to_seg_desc(&nt_desc);
@@ -705,13 +744,13 @@ vmexit_task_switch(struct vmctx *ctx, st
if (nt_type != SDT_SYS386BSY && nt_type != SDT_SYS386TSS &&
nt_type != SDT_SYS286BSY && nt_type != SDT_SYS286TSS) {
sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext);
- return (VMEXIT_RESTART);
+ goto done;
}
/* TSS descriptor must have present bit set */
if (!SEG_DESC_PRESENT(nt.access)) {
sel_exception(ctx, vcpu, IDT_NP, nt_sel, ext);
- return (VMEXIT_RESTART);
+ goto done;
}
/*
@@ -728,13 +767,13 @@ vmexit_task_switch(struct vmctx *ctx, st
assert(minlimit > 0);
if (nt.limit < minlimit) {
sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext);
- return (VMEXIT_RESTART);
+ goto done;
}
/* TSS must be busy if task switch is due to IRET */
if (reason == TSR_IRET && !TSS_BUSY(nt_type)) {
sel_exception(ctx, vcpu, IDT_TS, nt_sel, ext);
- return (VMEXIT_RESTART);
+ goto done;
}
/*
@@ -743,21 +782,14 @@ vmexit_task_switch(struct vmctx *ctx, st
*/
if (reason != TSR_IRET && TSS_BUSY(nt_type)) {
sel_exception(ctx, vcpu, IDT_GP, nt_sel, ext);
- return (VMEXIT_RESTART);
+ goto done;
}
/* Fetch the new TSS */
error = vm_copy_setup(ctx, vcpu, &sup_paging, nt.base, minlimit + 1,
PROT_READ | PROT_WRITE, nt_iov, nitems(nt_iov));
- if (error == 1) {
- /* Restart vcpu execution to handle the page fault */
- return (VMEXIT_RESTART);
- } else if (error == -1) {
- return (VMEXIT_ABORT);
- } else {
- assert(error == 0);
- vm_copyin(ctx, vcpu, nt_iov, &newtss, minlimit + 1);
- }
+ CHKERR(error);
+ vm_copyin(ctx, vcpu, nt_iov, &newtss, minlimit + 1);
/* Get the old TSS selector from the guest's task register */
ot_sel = GETREG(ctx, vcpu, VM_REG_GUEST_TR);
@@ -769,7 +801,7 @@ vmexit_task_switch(struct vmctx *ctx, st
* (sel = 0, base = 0, limit = 0xffff).
*/
sel_exception(ctx, vcpu, IDT_TS, ot_sel, task_switch->ext);
- return (VMEXIT_RESTART);
+ goto done;
}
/* Get the old TSS base and limit from the guest's task register */
@@ -781,24 +813,14 @@ vmexit_task_switch(struct vmctx *ctx, st
assert(ot_type == SDT_SYS386BSY || ot_type == SDT_SYS286BSY);
/* Fetch the old TSS descriptor */
- error = read_tss_descriptor(ctx, vcpu, task_switch, ot_sel,
- &ot_desc);
- if (error)
- return (error);
+ error = read_tss_descriptor(ctx, vcpu, task_switch, ot_sel, &ot_desc);
+ CHKERR(error);
/* Get the old TSS */
error = vm_copy_setup(ctx, vcpu, &sup_paging, ot_base, minlimit + 1,
PROT_READ | PROT_WRITE, ot_iov, nitems(ot_iov));
- if (error == 1) {
- /* Restart vcpu execution to handle the page fault */
- return (VMEXIT_RESTART);
- } else if (error == -1) {
- fprintf(stderr, "Error copying in old TSS: %d\n", errno);
- return (VMEXIT_ABORT);
- } else {
- assert(error == 0);
- vm_copyin(ctx, vcpu, ot_iov, &oldtss, minlimit + 1);
- }
+ CHKERR(error);
+ vm_copyin(ctx, vcpu, ot_iov, &oldtss, minlimit + 1);
/*
* Clear the busy bit in the old TSS descriptor if the task switch
@@ -808,8 +830,7 @@ vmexit_task_switch(struct vmctx *ctx, st
ot_desc.sd_type &= ~0x2;
error = desc_table_write(ctx, vcpu, &sup_paging, ot_sel,
&ot_desc);
- if (error)
- return (error);
+ CHKERR(error);
}
if (nt_type == SDT_SYS286BSY || nt_type == SDT_SYS286TSS) {
@@ -829,8 +850,7 @@ vmexit_task_switch(struct vmctx *ctx, st
nt_desc.sd_type |= 0x2;
error = desc_table_write(ctx, vcpu, &sup_paging, nt_sel,
&nt_desc);
- if (error)
- return (error);
+ CHKERR(error);
}
/* Update task register to point at the new TSS */
@@ -854,8 +874,7 @@ vmexit_task_switch(struct vmctx *ctx, st
/* Load processor state from new TSS */
error = tss32_restore(ctx, vcpu, task_switch, ot_sel, &newtss, nt_iov);
- if (error)
- return (error);
+ CHKERR(error);
/*
* Section "Interrupt Tasks" in Intel SDM, Vol 3: if an exception
@@ -867,9 +886,7 @@ vmexit_task_switch(struct vmctx *ctx, st
assert(task_switch->reason == TSR_IDT_GATE);
error = push_errcode(ctx, vcpu, &task_switch->paging, nt_type,
task_switch->errcode);
- if (error) {
- return (error);
- }
+ CHKERR(error);
}
/*
@@ -910,5 +927,6 @@ vmexit_task_switch(struct vmctx *ctx, st
/*
* XXX should inject debug exception if 'T' bit is 1
*/
- return (VMEXIT_RESTART);
+done:
+ return (VMEXIT_CONTINUE);
}
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