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    Subject[PATCH 5.10 113/154] KVM: PPC: Book3S HV: Use GLOBAL_TOC for kvmppc_h_set_dabr/xdabr()
    Date
    From: Michael Ellerman <mpe@ellerman.id.au>

    [ Upstream commit dae581864609d36fb58855fd59880b4941ce9d14 ]

    kvmppc_h_set_dabr(), and kvmppc_h_set_xdabr() which jumps into
    it, need to use _GLOBAL_TOC to setup the kernel TOC pointer, because
    kvmppc_h_set_dabr() uses LOAD_REG_ADDR() to load dawr_force_enable.

    When called from hcall_try_real_mode() we have the kernel TOC in r2,
    established near the start of kvmppc_interrupt_hv(), so there is no
    issue.

    But they can also be called from kvmppc_pseries_do_hcall() which is
    module code, so the access ends up happening with the kvm-hv module's
    r2, which will not point at dawr_force_enable and could even cause a
    fault.

    With the current code layout and compilers we haven't observed a fault
    in practice, the load hits somewhere in kvm-hv.ko and silently returns
    some bogus value.

    Note that we we expect p8/p9 guests to use the DAWR, but SLOF uses
    h_set_dabr() to test if sc1 works correctly, see SLOF's
    lib/libhvcall/brokensc1.c.

    Fixes: c1fe190c0672 ("powerpc: Add force enable of DAWR on P9 option")
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Reviewed-by: Daniel Axtens <dja@axtens.net>
    Link: https://lore.kernel.org/r/20210923151031.72408-1-mpe@ellerman.id.au
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kvm/book3s_hv_rmhandlers.S | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
    index db78123166a8b..b1d9afffd8419 100644
    --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
    +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
    @@ -2539,7 +2539,7 @@ hcall_real_table:
    .globl hcall_real_table_end
    hcall_real_table_end:

    -_GLOBAL(kvmppc_h_set_xdabr)
    +_GLOBAL_TOC(kvmppc_h_set_xdabr)
    EXPORT_SYMBOL_GPL(kvmppc_h_set_xdabr)
    andi. r0, r5, DABRX_USER | DABRX_KERNEL
    beq 6f
    @@ -2549,7 +2549,7 @@ EXPORT_SYMBOL_GPL(kvmppc_h_set_xdabr)
    6: li r3, H_PARAMETER
    blr

    -_GLOBAL(kvmppc_h_set_dabr)
    +_GLOBAL_TOC(kvmppc_h_set_dabr)
    EXPORT_SYMBOL_GPL(kvmppc_h_set_dabr)
    li r5, DABRX_USER | DABRX_KERNEL
    3:
    --
    2.33.0


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