On Fri, 17 Sep 2010, Blue Swirl wrote:
> On Fri, Sep 17, 2010 at 11:14 AM, <anthony.perard@xxxxxxxxxx> wrote:
> > From: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> >
> > Introduce a new emulated PCI device, specific to fully virtualized Xen
> > guests. The device is necessary for PV on HVM drivers to work.
> >
> > Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > ---
> > Makefile.target | 1 +
> > hw/hw.h | 3 +
> > hw/pci_ids.h | 2 +
> > hw/xen_machine_fv.c | 3 +
> > hw/xen_platform.c | 455
> > +++++++++++++++++++++++++++++++++++++++++++++++++++
> > hw/xen_platform.h | 8 +
> > 6 files changed, 472 insertions(+), 0 deletions(-)
> > create mode 100644 hw/xen_platform.c
> > create mode 100644 hw/xen_platform.h
[...]
> > +/* We throttle access to dom0 syslog, to avoid DOS attacks. This is
> > + modelled as a token bucket, with one token for every byte of log.
> > + The bucket size is 128KB (->1024 lines of 128 bytes each) and
> > + refills at 256B/s. It starts full. The guest is blocked if no
> > + tokens are available when it tries to generate a log message. */
> > +#define BUCKET_MAX_SIZE (128*1024)
> > +#define BUCKET_FILL_RATE 256
> > +
> > +static void throttle(PCIXenPlatformState *s, unsigned count)
> > +{
> > + static unsigned available;
> > + static struct timespec last_refil;
>
> last_refill
>
> > + static int started;
> > + static int warned;
> > +
> > + struct timespec waiting_for, now;
> > + double delay;
> > + struct timespec ts;
> > +
> > + if (s->throttling_disabled)
> > + return;
>
> Braces should be added here and other places.
>
> > +
> > + if (!started) {
> > + clock_gettime(CLOCK_MONOTONIC, &last_refil);
> > + available = BUCKET_MAX_SIZE;
> > + started = 1;
> > + }
> > +
> > + if (count > BUCKET_MAX_SIZE) {
> > + DPRINTF("tried to get %d tokens, but bucket size is %d\n",
>
> count is unsigned, so %u.
>
> > + BUCKET_MAX_SIZE, count);
> > + exit(1);
> > + }
> > +
> > + if (available < count) {
> > + /* The bucket is empty. Refil it */
> > +
> > + /* When will it be full enough to handle this request? */
> > + delay = (double)(count - available) / BUCKET_FILL_RATE;
> > + waiting_for = last_refil;
> > + waiting_for.tv_sec += delay;
> > + waiting_for.tv_nsec += (delay - (int)delay) * 1e9;
> > + if (waiting_for.tv_nsec >= 1000000000) {
> > + waiting_for.tv_nsec -= 1000000000;
> > + waiting_for.tv_sec++;
> > + }
> > +
> > + /* How long do we have to wait? (might be negative) */
> > + clock_gettime(CLOCK_MONOTONIC, &now);
> > + ts.tv_sec = waiting_for.tv_sec - now.tv_sec;
> > + ts.tv_nsec = waiting_for.tv_nsec - now.tv_nsec;
> > + if (ts.tv_nsec < 0) {
> > + ts.tv_sec--;
> > + ts.tv_nsec += 1000000000;
> > + }
> > +
> > + /* Wait for it. */
> > + if (ts.tv_sec > 0 ||
> > + (ts.tv_sec == 0 && ts.tv_nsec > 0)) {
> > + if (!warned) {
> > + DPRINTF("throttling guest access to syslog");
> > + warned = 1;
> > + }
> > + while (nanosleep(&ts, &ts) < 0 && errno == EINTR)
> > + ;
>
> braces
>
> > + }
> > +
> > + /* Refil */
>
> Refill
>
> > + clock_gettime(CLOCK_MONOTONIC, &now);
> > + delay = (now.tv_sec - last_refil.tv_sec) +
> > + (now.tv_nsec - last_refil.tv_nsec) * 1.0e-9;
> > + available += BUCKET_FILL_RATE * delay;
>
> We have muldiv64(), perhaps it could be used here?
Ok, I use it, and I also use qemu_get_clock_ns(rt_clock).
> > + if (available > BUCKET_MAX_SIZE)
> > + available = BUCKET_MAX_SIZE;
> > + last_refil = now;
> > + }
> > +
> > + assert(available >= count);
>
> Is it possible to trigger this from the guest?
I don't think we can do that for every guest.
> > +
> > + available -= count;
> > +}
> > +
[...]
> > +static uint32_t platform_mmio_read(void *opaque, target_phys_addr_t addr)
> > +{
> > + static int warnings = 0;
> > +
> > + if (warnings < 5) {
> > + DPRINTF("Warning: attempted read from physical address "
> > + "0x" TARGET_FMT_plx " in xen platform mmio space\n", addr);
> > + warnings++;
>
> Since DPRINTF only works in a specially compiled version, I'd remove
> these checks. There could also be additional debug flags besides
> PLATFORM_DEBUG to enable these warnings if these are too noisy, like
> DEBUG_MMIO. I'd rename PLATFORM_DEBUG to DEBUG_PLATFORM.
I will fix the coding style issue.
Thanks,
--
Anthony PERARD
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