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Re: [Qemu-devel] [PATCH KVM v2 2/4] KVM: additional i8254 output fixes
From: |
Gleb Natapov |
Subject: |
Re: [Qemu-devel] [PATCH KVM v2 2/4] KVM: additional i8254 output fixes |
Date: |
Mon, 7 Jan 2013 14:04:03 +0200 |
On Wed, Dec 26, 2012 at 10:39:54PM -0700, Matthew Ogilvie wrote:
> Make git_get_out() consistent with spec. Currently pit_get_out()
> doesn't affect IRQ0, but it can be read by the guest in other ways.
> This makes it consistent with proposed changes in qemu's i8254 model
> as well.
>
> See http://bochs.sourceforge.net/techspec/intel-82c54-timer.pdf.gz
> or search the net for 23124406.pdf.
>
> Signed-off-by: Matthew Ogilvie <address@hidden>
> ---
> arch/x86/kvm/i8254.c | 44 ++++++++++++++++++++++++++++++++++----------
> 1 file changed, 34 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index cd4ec60..fd38938 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -144,6 +144,10 @@ static int pit_get_count(struct kvm *kvm, int channel)
>
> WARN_ON(!mutex_is_locked(&kvm->arch.vpit->pit_state.lock));
>
> + /* FIXME: Add some way to represent a paused timer and return
> + * the paused-at counter value, to better model gate pausing,
> + * "wait until next CLK pulse to load counter" logic, etc.
> + */
> t = kpit_elapsed(kvm, c, channel);
> d = muldiv64(t, KVM_PIT_FREQ, NSEC_PER_SEC);
>
> @@ -155,8 +159,7 @@ static int pit_get_count(struct kvm *kvm, int channel)
> counter = (c->count - d) & 0xffff;
> break;
> case 3:
> - /* XXX: may be incorrect for odd counts */
> - counter = c->count - (mod_64((2 * d), c->count));
> + counter = (c->count - (mod_64((2 * d), c->count))) & 0xfffe;
> break;
> default:
> counter = c->count - mod_64(d, c->count);
> @@ -180,20 +183,18 @@ static int pit_get_out(struct kvm *kvm, int channel)
> switch (c->mode) {
> default:
> case 0:
> - out = (d >= c->count);
> - break;
> case 1:
> - out = (d < c->count);
> + out = (d >= c->count);
> break;
> case 2:
> - out = ((mod_64(d, c->count) == 0) && (d != 0));
> + out = (mod_64(d, c->count) != (c->count - 1) || c->gate == 0);
> break;
> case 3:
> - out = (mod_64(d, c->count) < ((c->count + 1) >> 1));
> + out = (mod_64(d, c->count) < ((c->count + 1) >> 1) || c->gate
> == 0);
> break;
> case 4:
> case 5:
> - out = (d == c->count);
> + out = (d != c->count);
> break;
> }
>
> @@ -367,7 +368,7 @@ static void pit_load_count(struct kvm *kvm, int channel,
> u32 val)
>
> /*
> * The largest possible initial count is 0; this is equivalent
> - * to 216 for binary counting and 104 for BCD counting.
> + * to pow(2,16) for binary counting and pow(10,4) for BCD counting.
> */
> if (val == 0)
> val = 0x10000;
> @@ -376,6 +377,26 @@ static void pit_load_count(struct kvm *kvm, int channel,
> u32 val)
>
> if (channel != 0) {
> ps->channels[channel].count_load_time = ktime_get();
> +
> + /* In gate-triggered one-shot modes,
> + * indirectly model some pit_get_out()
> + * cases by setting the load time way
> + * back until gate-triggered.
> + * (Generally only affects reading status
> + * from channel 2 speaker,
> + * due to hard-wired gates on other
> + * channels.)
> + *
> + * FIXME: This might be redesigned if a paused
> + * timer state is added for pit_get_count().
> + */
> + if (ps->channels[channel].mode == 1 ||
> + ps->channels[channel].mode == 5) {
> + u64 delta = muldiv64(val+2, NSEC_PER_SEC, KVM_PIT_FREQ);
> + ps->channels[channel].count_load_time =
> + ktime_sub(ps->channels[channel].count_load_time,
> + ns_to_ktime(delta));
I do not understand what are you trying to do here. You assume that
trigger will happen 2 clocks after counter is loaded?
> + }
> return;
> }
>
> @@ -383,7 +404,6 @@ static void pit_load_count(struct kvm *kvm, int channel,
> u32 val)
> * mode 1 is one shot, mode 2 is period, otherwise del timer */
> switch (ps->channels[0].mode) {
> case 0:
> - case 1:
> /* FIXME: enhance mode 4 precision */
> case 4:
> create_pit_timer(kvm, val, 0);
> @@ -393,6 +413,10 @@ static void pit_load_count(struct kvm *kvm, int channel,
> u32 val)
> create_pit_timer(kvm, val, 1);
> break;
> default:
> + /* Modes 1 and 5 are triggered by gate leading edge,
> + * but channel 0's gate is hard-wired high and has
> + * no edges (on normal real hardware).
> + */
> destroy_pit_timer(kvm->arch.vpit);
> }
> }
> --
> 1.7.10.2.484.gcd07cc5
--
Gleb.
- Re: [Qemu-devel] [PATCH KVM v2 2/4] KVM: additional i8254 output fixes,
Gleb Natapov <=