lkml.org 
[lkml]   [2019]   [Nov]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.14 121/122] powerpc/time: Fix clockevent_decrementer initalisation for PR KVM
    Date
    From: Michael Ellerman <mpe@ellerman.id.au>

    [ Upstream commit b4d16ab58c41ff0125822464bdff074cebd0fe47 ]

    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.

    Fixes: 8b78fdb045de ("powerpc/time: Use clockevents_register_device(), fixing an issue with large decrementer")
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 870e75d304591..7c7c5a16284d2 100644
    --- a/arch/powerpc/kernel/time.c
    +++ b/arch/powerpc/kernel/time.c
    @@ -988,6 +988,10 @@ 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)
    --
    2.20.1


    \
     
     \ /
      Last update: 2019-11-22 11:56    [W:4.179 / U:0.364 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site