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    Subject[PATCH v3 10/13] x86/retpoline/pvops: Convert assembler indirect jumps
    Date
    Convert pvops invocations to use non-speculative call sequences, when
    CONFIG_RETPOLINE is enabled.

    There is scope for future optimisation here — once the pvops methods are
    actually set, we could just turn the damn things into *direct* jumps.
    But this is perfectly sufficient for now, without that added complexity.

    Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
    ---
    arch/x86/include/asm/paravirt_types.h | 14 ++++++++++++--
    1 file changed, 12 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
    index 6ec54d01972d..54b735b8ae12 100644
    --- a/arch/x86/include/asm/paravirt_types.h
    +++ b/arch/x86/include/asm/paravirt_types.h
    @@ -336,11 +336,17 @@ extern struct pv_lock_ops pv_lock_ops;
    #define PARAVIRT_PATCH(x) \
    (offsetof(struct paravirt_patch_template, x) / sizeof(void *))

    +#define paravirt_clobber(clobber) \
    + [paravirt_clobber] "i" (clobber)
    +#ifdef CONFIG_RETPOLINE
    +#define paravirt_type(op) \
    + [paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \
    + [paravirt_opptr] "r" ((op))
    +#else
    #define paravirt_type(op) \
    [paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \
    [paravirt_opptr] "i" (&(op))
    -#define paravirt_clobber(clobber) \
    - [paravirt_clobber] "i" (clobber)
    +#endif

    /*
    * Generate some code, and mark it as patchable by the
    @@ -392,7 +398,11 @@ int paravirt_disable_iospace(void);
    * offset into the paravirt_patch_template structure, and can therefore be
    * freely converted back into a structure offset.
    */
    +#ifdef CONFIG_RETPOLINE
    +#define PARAVIRT_CALL "call __x86.indirect_thunk.%V[paravirt_opptr];"
    +#else
    #define PARAVIRT_CALL "call *%c[paravirt_opptr];"
    +#endif

    /*
    * These macros are intended to wrap calls through one of the paravirt
    --
    2.14.3
    \
     
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