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    Subject[PATCH 5.2 200/215] powerpc/pmu: Set pmcregs_in_use in paca when running as LPAR
    Date
    From: Suraj Jitindar Singh <sjitindarsingh@gmail.com>

    commit 28d2a6e6684d9851905f379816d8a4d03587ed94 upstream.

    The ability to run nested guests under KVM means that a guest can also
    act as a hypervisor for it's own nested guest. Currently
    ppc_set_pmu_inuse() assumes that either FW_FEATURE_LPAR is set,
    indicating a guest environment, and so sets the pmcregs_in_use flag in
    the lppaca, or that it isn't set, indicating a hypervisor environment,
    and so sets the pmcregs_in_use flag in the paca.

    The pmcregs_in_use flag in the lppaca is used to communicate this
    information to a hypervisor and so must be set in a guest environment.
    The pmcregs_in_use flag in the paca is used by KVM code to determine
    whether the host state of the performance monitoring unit (PMU) must
    be saved and restored when running a guest.

    Thus when a guest also acts as a hypervisor it must set this bit in
    both places since it needs to ensure both that the real hypervisor
    saves it's PMU registers when it runs (requires pmcregs_in_use flag in
    lppaca), and that it saves it's own PMU registers when running a
    nested guest (requires pmcregs_in_use flag in paca).

    Modify ppc_set_pmu_inuse() so that the pmcregs_in_use bit is set in
    both the lppaca and the paca when a guest (LPAR) is running with the
    capability of running it's own guests (CONFIG_KVM_BOOK3S_HV_POSSIBLE).

    Fixes: 95a6432ce903 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests")
    Cc: stable@vger.kernel.org # v4.20+
    Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20190703012022.15644-2-sjitindarsingh@gmail.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/powerpc/include/asm/pmc.h | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)

    --- a/arch/powerpc/include/asm/pmc.h
    +++ b/arch/powerpc/include/asm/pmc.h
    @@ -27,11 +27,10 @@ static inline void ppc_set_pmu_inuse(int
    #ifdef CONFIG_PPC_PSERIES
    get_lppaca()->pmcregs_in_use = inuse;
    #endif
    - } else {
    + }
    #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
    - get_paca()->pmcregs_in_use = inuse;
    + get_paca()->pmcregs_in_use = inuse;
    #endif
    - }
    #endif
    }


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