* __thread variables). So we have a hypercall specifically for this case. */
static void lguest_load_tls(struct thread_struct *t, unsigned int cpu)
{
+ /* There's one problem which normal hardware doesn't have: the Host
+ * can't handle us removing entries we're currently using. So we clear
+ * the GS register here: if it's needed it'll be reloaded anyway. */
+ loadsegment(gs, 0);
lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0);
}
-/*:*/
/*G:038 That's enough excitement for now, back to ploughing through each of
* the paravirt_ops (we're about 1/3 of the way through).
* Time.
*
* It would be far better for everyone if the Guest had its own clock, but
- * until then it must ask the Host for the time.
+ * until then the Host gives us the time on every interrupt.
*/
static unsigned long lguest_get_wallclock(void)
{
- return hcall(LHCALL_GET_WALLCLOCK, 0, 0, 0);
+ return lguest_data.time.tv_sec;
}
-/* If the Host tells us we can trust the TSC, we use that, otherwise we simply
- * use the imprecise but reliable "jiffies" counter. */
static cycle_t lguest_clock_read(void)
{
+ unsigned long sec, nsec;
+
+ /* If the Host tells the TSC speed, we can trust that. */
if (lguest_data.tsc_khz)
return native_read_tsc();
- else
- return jiffies;
+
+ /* If we can't use the TSC, we read the time value written by the Host.
+ * Since it's in two parts (seconds and nanoseconds), we risk reading
+ * it just as it's changing from 99 & 0.999999999 to 100 and 0, and
+ * getting 99 and 0. As Linux tends to come apart under the stress of
+ * time travel, we must be careful: */
+ do {
+ /* First we read the seconds part. */
+ sec = lguest_data.time.tv_sec;
+ /* This read memory barrier tells the compiler and the CPU that
+ * this can't be reordered: we have to complete the above
+ * before going on. */
+ rmb();
+ /* Now we read the nanoseconds part. */
+ nsec = lguest_data.time.tv_nsec;
+ /* Make sure we've done that. */
+ rmb();
+ /* Now if the seconds part has changed, try again. */
+ } while (unlikely(lguest_data.time.tv_sec != sec));
+
+ /* Our non-TSC clock is in real nanoseconds. */
+ return sec*1000000000ULL + nsec;
}
/* This is what we tell the kernel is our clocksource. */
.name = "lguest",
.rating = 400,
.read = lguest_clock_read,
+ .mask = CLOCKSOURCE_MASK(64),
+ .mult = 1 << 22,
+ .shift = 22,
};
+/* The "scheduler clock" is just our real clock, adjusted to start at zero */
static unsigned long long lguest_sched_clock(void)
{
return cyc2ns(&lguest_clock, lguest_clock_read() - clock_base);
set_irq_handler(0, lguest_time_irq);
/* Our clock structure look like arch/i386/kernel/tsc.c if we can use
- * the TSC, otherwise it looks like kernel/time/jiffies.c. Either way,
- * the "rating" is initialized so high that it's always chosen over any
- * other clocksource. */
+ * the TSC, otherwise it's a dumb nanosecond-resolution clock. Either
+ * way, the "rating" is initialized so high that it's always chosen
+ * over any other clocksource. */
if (lguest_data.tsc_khz) {
- lguest_clock.shift = 22;
lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz,
lguest_clock.shift);
- lguest_clock.mask = CLOCKSOURCE_MASK(64);
lguest_clock.flags = CLOCK_SOURCE_IS_CONTINUOUS;
- } else {
- /* To understand this, start at kernel/time/jiffies.c... */
- lguest_clock.shift = 8;
- lguest_clock.mult = (((u64)NSEC_PER_SEC<<8)/ACTHZ) << 8;
- lguest_clock.mask = CLOCKSOURCE_MASK(32);
}
clock_base = lguest_clock_read();
clocksource_register(&lguest_clock);
+ /* Now we've set up our clock, we can use it as the scheduler clock */
+ paravirt_ops.sched_clock = lguest_sched_clock;
+
/* We can't set cpumask in the initializer: damn C limitations! Set it
* here and register our timer device. */
lguest_clockevent.cpumask = cpumask_of_cpu(0);
/* Now our patch routine is fairly simple (based on the native one in
* paravirt.c). If we have a replacement, we copy it in and return how much of
* the available space we used. */
-static unsigned lguest_patch(u8 type, u16 clobber, void *insns, unsigned len)
+static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
+ unsigned long addr, unsigned len)
{
unsigned int insn_len;
/* Don't do anything special if we don't have a replacement */
if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start)
- return paravirt_patch_default(type, clobber, insns, len);
+ return paravirt_patch_default(type, clobber, ibuf, addr, len);
insn_len = lguest_insns[type].end - lguest_insns[type].start;
/* Similarly if we can't fit replacement (shouldn't happen, but let's
* be thorough). */
if (len < insn_len)
- return paravirt_patch_default(type, clobber, insns, len);
+ return paravirt_patch_default(type, clobber, ibuf, addr, len);
/* Copy in our instructions. */
- memcpy(insns, lguest_insns[type].start, insn_len);
+ memcpy(ibuf, lguest_insns[type].start, insn_len);
return insn_len;
}
paravirt_ops.time_init = lguest_time_init;
paravirt_ops.set_lazy_mode = lguest_lazy_mode;
paravirt_ops.wbinvd = lguest_wbinvd;
- paravirt_ops.sched_clock = lguest_sched_clock;
/* Now is a good time to look at the implementations of these functions
* before returning to the rest of lguest_init(). */
* the normal data segment to get through booting. */
asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");
+ /* Clear the part of the kernel data which is expected to be zero.
+ * Normally it will be anyway, but if we're loading from a bzImage with
+ * CONFIG_RELOCATALE=y, the relocations will be sitting here. */
+ memset(__bss_start, 0, __bss_stop - __bss_start);
+
/* The Host uses the top of the Guest's virtual address space for the
* Host<->Guest Switcher, and it tells us how much it needs in
* lguest_data.reserve_mem, set up on the LGUEST_INIT hypercall. */
projects / linux-2.6 / blobdiff