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Re: [Qemu-ppc] [PATCH 2/3] ppc: add support for timebase migration on no
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [PATCH 2/3] ppc: add support for timebase migration on non-PPC hosts |
Date: |
Mon, 1 Feb 2016 12:19:08 +1100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Sun, Jan 31, 2016 at 07:19:35PM +0000, Mark Cave-Ayland wrote:
> This patch provides support for migration of the PPC guest timebase on non-PPC
> host architectures (i.e those using QEMU's virtual emulated timebase).
>
> Signed-off-by: Mark Cave-Ayland <address@hidden>
We shouldn't need an explicit test for a ppc host. Instead we should
never be touching any host-dependent ticks values, only using host
side interfaces which work in realtime units like ns.
Worse, the ppc host variants here will still be wrong if the host has
a different timebase frequency to the guest, which will always be true
for a g3beige (16MHz) on a modern ppc host (512 MHz).
> ---
> hw/ppc/ppc.c | 33 +++++++++++++++++++++++++++------
> 1 file changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
> index 19f4570..9b80c1d 100644
> --- a/hw/ppc/ppc.c
> +++ b/hw/ppc/ppc.c
> @@ -832,6 +832,15 @@ static void cpu_ppc_set_tb_clk (void *opaque, uint32_t
> freq)
> cpu_ppc_store_purr(cpu, 0x0000000000000000ULL);
> }
>
> +static int host_cpu_is_ppc(void)
> +{
> +#if defined(_ARCH_PPC)
> + return -1;
> +#else
> + return 0;
> +#endif
> +}
> +
> static void timebase_pre_save(void *opaque)
> {
> PPCTimebase *tb = opaque;
> @@ -844,11 +853,16 @@ static void timebase_pre_save(void *opaque)
> }
>
> tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
> - /*
> - * tb_offset is only expected to be changed by migration so
> - * there is no need to update it from KVM here
> - */
> - tb->guest_timebase = ticks + first_ppc_cpu->env.tb_env->tb_offset;
> +
> + if (host_cpu_is_ppc()) {
> + /*
> + * tb_offset is only expected to be changed by migration so
> + * there is no need to update it from KVM here
> + */
> + tb->guest_timebase = ticks + first_ppc_cpu->env.tb_env->tb_offset;
> + } else {
> + tb->guest_timebase = cpu_ppc_load_tbl(&first_ppc_cpu->env);
> + }
> }
>
> static int timebase_post_load(void *opaque, int version_id)
> @@ -879,7 +893,14 @@ static int timebase_post_load(void *opaque, int
> version_id)
> NANOSECONDS_PER_SECOND);
> guest_tb = tb_remote->guest_timebase + migration_duration_tb;
>
> - tb_off_adj = guest_tb - cpu_get_host_ticks();
> + if (host_cpu_is_ppc()) {
> + /* Hardware timebase */
> + tb_off_adj = guest_tb - cpu_get_host_ticks();
> + } else {
> + /* Software timebase */
> + tb_off_adj = guest_tb -
> muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
> + freq, get_ticks_per_sec());
> + }
>
> tb_off = first_ppc_cpu->env.tb_env->tb_offset;
> trace_ppc_tb_adjust(tb_off, tb_off_adj, tb_off_adj - tb_off,
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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