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    Subject[PATCH 5.9 659/757] x86/mce: Annotate mce_rd/wrmsrl() with noinstr
    Date
    From: Borislav Petkov <bp@suse.de>

    [ Upstream commit e100777016fdf6ec3a9d7c1773b15a2b5eca6c55 ]

    They do get called from the #MC handler which is already marked
    "noinstr".

    Commit

    e2def7d49d08 ("x86/mce: Make mce_rdmsrl() panic on an inaccessible MSR")

    already got rid of the instrumentation in the MSR accessors, fix the
    annotation now too, in order to get rid of:

    vmlinux.o: warning: objtool: do_machine_check()+0x4a: call to mce_rdmsrl() leaves .noinstr.text section

    Signed-off-by: Borislav Petkov <bp@suse.de>
    Link: https://lkml.kernel.org/r/20200915194020.28807-1-bp@alien8.de
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kernel/cpu/mce/core.c | 27 +++++++++++++++++++++------
    1 file changed, 21 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
    index fc4f8c04bdb56..4288645425f15 100644
    --- a/arch/x86/kernel/cpu/mce/core.c
    +++ b/arch/x86/kernel/cpu/mce/core.c
    @@ -374,16 +374,25 @@ static int msr_to_offset(u32 msr)
    }

    /* MSR access wrappers used for error injection */
    -static u64 mce_rdmsrl(u32 msr)
    +static noinstr u64 mce_rdmsrl(u32 msr)
    {
    u64 v;

    if (__this_cpu_read(injectm.finished)) {
    - int offset = msr_to_offset(msr);
    + int offset;
    + u64 ret;

    + instrumentation_begin();
    +
    + offset = msr_to_offset(msr);
    if (offset < 0)
    - return 0;
    - return *(u64 *)((char *)this_cpu_ptr(&injectm) + offset);
    + ret = 0;
    + else
    + ret = *(u64 *)((char *)this_cpu_ptr(&injectm) + offset);
    +
    + instrumentation_end();
    +
    + return ret;
    }

    if (rdmsrl_safe(msr, &v)) {
    @@ -399,13 +408,19 @@ static u64 mce_rdmsrl(u32 msr)
    return v;
    }

    -static void mce_wrmsrl(u32 msr, u64 v)
    +static noinstr void mce_wrmsrl(u32 msr, u64 v)
    {
    if (__this_cpu_read(injectm.finished)) {
    - int offset = msr_to_offset(msr);
    + int offset;

    + instrumentation_begin();
    +
    + offset = msr_to_offset(msr);
    if (offset >= 0)
    *(u64 *)((char *)this_cpu_ptr(&injectm) + offset) = v;
    +
    + instrumentation_end();
    +
    return;
    }
    wrmsrl(msr, v);
    --
    2.25.1


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