From: Anton Blanchard <anton@ozlabs.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@ozlabs.org, paulus@samba.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH] powerpc/time: Fix clockevent_decrementer initalisation for PR KVM
Date: Sat, 20 Oct 2018 06:59:23 +0000 [thread overview]
Message-ID: <20181020175923.4cbc5434@kryten> (raw)
In-Reply-To: <20181019042319.9457-1-mpe@ellerman.id.au>
On Fri, 19 Oct 2018 15:23:19 +1100
Michael Ellerman <mpe@ellerman.id.au> wrote:
> In the recent commit 8b78fdb045de ("powerpc/time: Use
> clockevents_register_device(), fixing an issue with large
> decrementer") we changed the way we initialise the decrementer
> clockevent(s).
>
> We no longer initialise the mult & shift values of
> decrementer_clockevent itself.
>
> This has the effect of breaking PR KVM, because it uses those values
> in kvmppc_emulate_dec(). The symptom is guest kernels spin forever
> mid-way through boot.
>
> For now fix it by assigning back to decrementer_clockevent the mult
> and shift values.
Thanks Michael, I missed that completely.
Acked-by: Anton Blanchard <anton@samba.org>
Anton
>
> Fixes: 8b78fdb045de ("powerpc/time: Use
> clockevents_register_device(), fixing an issue with large
> decrementer") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> ---
> arch/powerpc/kernel/time.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index 40868f3ee113..68e8f963d108 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -989,6 +989,10 @@ static void register_decrementer_clockevent(int
> cpu)
> printk_once(KERN_DEBUG "clockevent: %s mult[%x] shift[%d]
> cpu[%d]\n", dec->name, dec->mult, dec->shift, cpu);
> +
> + /* Set values for KVM, see kvm_emulate_dec() */
> + decrementer_clockevent.mult = dec->mult;
> + decrementer_clockevent.shift = dec->shift;
> }
>
> static void enable_large_decrementer(void)
WARNING: multiple messages have this Message-ID (diff)
From: Anton Blanchard <anton@ozlabs.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@ozlabs.org, paulus@samba.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH] powerpc/time: Fix clockevent_decrementer initalisation for PR KVM
Date: Sat, 20 Oct 2018 17:59:23 +1100 [thread overview]
Message-ID: <20181020175923.4cbc5434@kryten> (raw)
In-Reply-To: <20181019042319.9457-1-mpe@ellerman.id.au>
On Fri, 19 Oct 2018 15:23:19 +1100
Michael Ellerman <mpe@ellerman.id.au> wrote:
> In the recent commit 8b78fdb045de ("powerpc/time: Use
> clockevents_register_device(), fixing an issue with large
> decrementer") we changed the way we initialise the decrementer
> clockevent(s).
>
> We no longer initialise the mult & shift values of
> decrementer_clockevent itself.
>
> This has the effect of breaking PR KVM, because it uses those values
> in kvmppc_emulate_dec(). The symptom is guest kernels spin forever
> mid-way through boot.
>
> For now fix it by assigning back to decrementer_clockevent the mult
> and shift values.
Thanks Michael, I missed that completely.
Acked-by: Anton Blanchard <anton@samba.org>
Anton
>
> Fixes: 8b78fdb045de ("powerpc/time: Use
> clockevents_register_device(), fixing an issue with large
> decrementer") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> ---
> arch/powerpc/kernel/time.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index 40868f3ee113..68e8f963d108 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -989,6 +989,10 @@ static void register_decrementer_clockevent(int
> cpu)
> printk_once(KERN_DEBUG "clockevent: %s mult[%x] shift[%d]
> cpu[%d]\n", dec->name, dec->mult, dec->shift, cpu);
> +
> + /* Set values for KVM, see kvm_emulate_dec() */
> + decrementer_clockevent.mult = dec->mult;
> + decrementer_clockevent.shift = dec->shift;
> }
>
> static void enable_large_decrementer(void)
next prev parent reply other threads:[~2018-10-20 6:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-19 4:23 [PATCH] powerpc/time: Fix clockevent_decrementer initalisation for PR KVM Michael Ellerman
2018-10-19 4:23 ` Michael Ellerman
2018-10-20 6:59 ` Anton Blanchard [this message]
2018-10-20 6:59 ` Anton Blanchard
2018-10-22 9:40 ` Michael Ellerman
2018-10-22 9:40 ` Michael Ellerman
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