Re: [PATCH v2 07/28] cputlb: Provide cpu_(ld, st}*_mmuidx_ra for user-only

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> This finishes the new interface began with the previous patch.
> Document the interface and deprecate MMU_MODE<N>_SUFFIX.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  include/exec/cpu_ldst.h     |  80 +++++++++++++-
>  docs/devel/loads-stores.rst | 211 ++++++++++++++++++++++++++----------
>  2 files changed, 230 insertions(+), 61 deletions(-)
>
> diff --git a/include/exec/cpu_ldst.h b/include/exec/cpu_ldst.h
> index ef59ed61e4..41b98ba801 100644
> --- a/include/exec/cpu_ldst.h
> +++ b/include/exec/cpu_ldst.h
> @@ -25,9 +25,13 @@
>   *
>   * The syntax for the accessors is:
>   *
> - * load: cpu_ld{sign}{size}_{mmusuffix}(env, ptr)
> + * load:  cpu_ld{sign}{size}_{mmusuffix}(env, ptr)
> + *        cpu_ld{sign}{size}_{mmusuffix}_ra(env, ptr, retaddr)
> + *        cpu_ld{sign}{size}_mmuidx_ra(env, ptr, mmu_idx, retaddr)
>   *
> - * store: cpu_st{sign}{size}_{mmusuffix}(env, ptr, val)
> + * store: cpu_st{size}_{mmusuffix}(env, ptr, val)
> + *        cpu_st{size}_{mmusuffix}_ra(env, ptr, val, retaddr)
> + *        cpu_st{size}_mmuidx_ra(env, ptr, val, mmu_idx, retaddr)
>   *
>   * sign is:
>   * (empty): for 32 and 64 bit sizes
> @@ -40,9 +44,10 @@
>   *   l: 32 bits
>   *   q: 64 bits
>   *
> - * mmusuffix is one of the generic suffixes "data" or "code", or
> - * (for softmmu configs)  a target-specific MMU mode suffix as defined
> - * in target cpu.h.
> + * mmusuffix is one of the generic suffixes "data" or "code", or "mmuidx".
> + * The "mmuidx" suffix carries an extra mmu_idx argument that specifies
> + * the index to use; the "data" and "code" suffixes take the index from
> + * cpu_mmu_index().
>   */
>  #ifndef CPU_LDST_H
>  #define CPU_LDST_H
> @@ -145,6 +150,71 @@ static inline void clear_helper_retaddr(void)
>  #undef MEMSUFFIX
>  #undef CODE_ACCESS
>  
> +/*
> + * Provide the same *_mmuidx_ra interface as for softmmu.
> + * The mmu_idx argument is ignored.
> + */
> +
> +static inline uint32_t cpu_ldub_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                          int mmu_idx, uintptr_t ra)
> +{
> +    return cpu_ldub_data_ra(env, addr, ra);
> +}
> +
> +static inline uint32_t cpu_lduw_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                          int mmu_idx, uintptr_t ra)
> +{
> +    return cpu_lduw_data_ra(env, addr, ra);
> +}
> +
> +static inline uint32_t cpu_ldl_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                         int mmu_idx, uintptr_t ra)
> +{
> +    return cpu_ldl_data_ra(env, addr, ra);
> +}
> +
> +static inline uint64_t cpu_ldq_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                         int mmu_idx, uintptr_t ra)
> +{
> +    return cpu_ldq_data_ra(env, addr, ra);
> +}
> +
> +static inline int cpu_ldsb_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                     int mmu_idx, uintptr_t ra)
> +{
> +    return cpu_ldsb_data_ra(env, addr, ra);
> +}
> +
> +static inline int cpu_ldsw_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                     int mmu_idx, uintptr_t ra)
> +{
> +    return cpu_ldsw_data_ra(env, addr, ra);
> +}
> +
> +static inline void cpu_stb_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                     uint32_t val, int mmu_idx, uintptr_t ra)
> +{
> +    cpu_stb_data_ra(env, addr, val, ra);
> +}
> +
> +static inline void cpu_stw_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                     uint32_t val, int mmu_idx, uintptr_t ra)
> +{
> +    cpu_stw_data_ra(env, addr, val, ra);
> +}
> +
> +static inline void cpu_stl_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                     uint32_t val, int mmu_idx, uintptr_t ra)
> +{
> +    cpu_stl_data_ra(env, addr, val, ra);
> +}
> +
> +static inline void cpu_stq_mmuidx_ra(CPUArchState *env, abi_ptr addr,
> +                                     uint64_t val, int mmu_idx, uintptr_t ra)
> +{
> +    cpu_stq_data_ra(env, addr, val, ra);
> +}
> +
>  #else
>  
>  /* Needed for TCG_OVERSIZED_GUEST */
> diff --git a/docs/devel/loads-stores.rst b/docs/devel/loads-stores.rst
> index 8a5bc912a5..03aa9e7ff8 100644
> --- a/docs/devel/loads-stores.rst
> +++ b/docs/devel/loads-stores.rst
> @@ -72,31 +72,34 @@ Regexes for git grep
>   - ``\<ldn_\([hbl]e\)?_p\>``
>   - ``\<stn_\([hbl]e\)?_p\>``
>  
> -``cpu_{ld,st}_*``
> -~~~~~~~~~~~~~~~~~
> +``cpu_{ld,st}*_mmuidx_ra``
> +~~~~~~~~~~~~~~~~~~~~~~~~~~
>  
> -These functions operate on a guest virtual address. Be aware
> -that these functions may cause a guest CPU exception to be
> -taken (e.g. for an alignment fault or MMU fault) which will
> -result in guest CPU state being updated and control longjumping
> -out of the function call. They should therefore only be used
> -in code that is implementing emulation of the target CPU.
> +These functions operate on a guest virtual address plus a context,
> +known as a "mmu index" or ``mmuidx``, which controls how that virtual
> +address is translated.  The meaning of the indexes are target specific,
> +but specifying a particular index might be necessary if, for instance,
> +the helper requires an "always as non-privileged" access rather that
> +the default access for the current state of the guest CPU.
>  
> -These functions may throw an exception (longjmp() back out
> -to the top level TCG loop). This means they must only be used
> -from helper functions where the translator has saved all
> -necessary CPU state before generating the helper function call.
> -It's usually better to use the ``_ra`` variants described below
> -from helper functions, but these functions are the right choice
> -for calls made from hooks like the CPU do_interrupt hook or
> -when you know for certain that the translator had to save all
> -the CPU state that ``cpu_restore_state()`` would restore anyway.
> +These functions may cause a guest CPU exception to be taken
> +(e.g. for an alignment fault or MMU fault) which will result in
> +guest CPU state being updated and control longjmp'ing out of the
> +function call.  They should therefore only be used in code that is
> +implementing emulation of the guest CPU.
> +
> +The ``retaddr`` parameter is used to control unwinding of the
> +guest CPU state in case of a guest CPU exception.  This is passed
> +to ``cpu_restore_state()``.  Therefore the value should either be 0,
> +to indicate that the guest CPU state is already synchronized, or
> +the result of ``GETPC()`` from the top level ``HELPER(foo)``
> +function, which is a return address into the generated code.
>  
>  Function names follow the pattern:
>  
> -load: ``cpu_ld{sign}{size}_{mmusuffix}(env, ptr)``
> +load: ``cpu_ld{sign}{size}_mmuidx_ra(env, ptr, mmuidx, retaddr)``
>  
> -store: ``cpu_st{size}_{mmusuffix}(env, ptr, val)``
> +store: ``cpu_st{size}_mmuidx_ra(env, ptr, val, mmuidx, retaddr)``
>  
>  ``sign``
>   - (empty) : for 32 or 64 bit sizes
> @@ -109,56 +112,151 @@ store: ``cpu_st{size}_{mmusuffix}(env, ptr, val)``
>   - ``l`` : 32 bits
>   - ``q`` : 64 bits
>  
> -``mmusuffix`` is one of the generic suffixes ``data`` or ``code``, or
> -(for softmmu configs) a target-specific MMU mode suffix as defined
> -in the target's ``cpu.h``.
> +Regexes for git grep:
> + - ``\<cpu_ld[us]\?[bwlq]_mmuidx_ra\>``
> + - ``\<cpu_st[bwlq]_mmuidx_ra\>``
>  
> -Regexes for git grep
> - - ``\<cpu_ld[us]\?[bwlq]_[a-zA-Z0-9]\+\>``
> - - ``\<cpu_st[bwlq]_[a-zA-Z0-9]\+\>``
> +``cpu_{ld,st}*_data_ra``
> +~~~~~~~~~~~~~~~~~~~~~~~~
>  
> -``cpu_{ld,st}_*_ra``
> -~~~~~~~~~~~~~~~~~~~~
> -
> -These functions work like the ``cpu_{ld,st}_*`` functions except
> -that they also take a ``retaddr`` argument. This extra argument
> -allows for correct unwinding of any exception that is taken,
> -and should generally be the result of GETPC() called directly
> -from the top level HELPER(foo) function (i.e. the return address
> -in the generated code).
> +These functions work like the ``cpu_{ld,st}_mmuidx_ra`` functions
> +except that the ``mmuidx`` parameter is taken from the current mode
> +of the guest CPU, as determined by ``cpu_mmu_index(env, false)``.
>  
>  These are generally the preferred way to do accesses by guest
> -virtual address from helper functions; see the documentation
> -of the non-``_ra`` variants for when those would be better.
> -
> -Calling these functions with a ``retaddr`` argument of 0 is
> -equivalent to calling the non-``_ra`` version of the function.
> +virtual address from helper functions, unless the access should
> +be performed with a context other than the default.
>  
>  Function names follow the pattern:
>  
> -load: ``cpu_ld{sign}{size}_{mmusuffix}_ra(env, ptr, retaddr)``
> +load: ``cpu_ld{sign}{size}_data_ra(env, ptr, ra)``
>  
> -store: ``cpu_st{sign}{size}_{mmusuffix}_ra(env, ptr, val, retaddr)``
> +store: ``cpu_st{size}_data_ra(env, ptr, val, ra)``
> +
> +``sign``
> + - (empty) : for 32 or 64 bit sizes
> + - ``u`` : unsigned
> + - ``s`` : signed
> +
> +``size``
> + - ``b`` : 8 bits
> + - ``w`` : 16 bits
> + - ``l`` : 32 bits
> + - ``q`` : 64 bits
> +
> +Regexes for git grep:
> + - ``\<cpu_ld[us]\?[bwlq]_data_ra\>``
> + - ``\<cpu_st[bwlq]_data_ra\>``
> +
> +``cpu_{ld,st}*_data``
> +~~~~~~~~~~~~~~~~~~~~~
> +
> +These functions work like the ``cpu_{ld,st}_data_ra`` functions
> +except that the ``retaddr`` parameter is 0, and thus does not
> +unwind guest CPU state.
> +
> +This means they must only be used from helper functions where the
> +translator has saved all necessary CPU state.  These functions are
> +the right choice for calls made from hooks like the CPU ``do_interrupt``
> +hook or when you know for certain that the translator had to save all
> +the CPU state anyway.
> +
> +Function names follow the pattern:
> +
> +load: ``cpu_ld{sign}{size}_data(env, ptr)``
> +
> +store: ``cpu_st{size}_data(env, ptr, val)``
> +
> +``sign``
> + - (empty) : for 32 or 64 bit sizes
> + - ``u`` : unsigned
> + - ``s`` : signed
> +
> +``size``
> + - ``b`` : 8 bits
> + - ``w`` : 16 bits
> + - ``l`` : 32 bits
> + - ``q`` : 64 bits
>  
>  Regexes for git grep
> - - ``\<cpu_ld[us]\?[bwlq]_[a-zA-Z0-9]\+_ra\>``
> - - ``\<cpu_st[bwlq]_[a-zA-Z0-9]\+_ra\>``
> + - ``\<cpu_ld[us]\?[bwlq]_data\>``
> + - ``\<cpu_st[bwlq]_data\+\>``
>  
> -``helper_*_{ld,st}*mmu``
> -~~~~~~~~~~~~~~~~~~~~~~~~
> +``cpu_ld*_code``
> +~~~~~~~~~~~~~~~~
> +
> +These functions perform a read for instruction execution.  The ``mmuidx``
> +parameter is taken from the current mode of the guest CPU, as determined
> +by ``cpu_mmu_index(env, true)``.  The ``retaddr`` parameter is 0, and
> +thus does not unwind guest CPU state, because CPU state is always
> +synchronized while translating instructions.  Any guest CPU exception
> +that is raised will indicate an instruction execution fault rather than
> +a data read fault.
> +
> +In general these functions should not be used directly during translation.
> +There are wrapper functions that are to be used which also take care of
> +plugins for tracing.
> +
> +Function names follow the pattern:
> +
> +load: ``cpu_ld{sign}{size}_code(env, ptr)``
> +
> +``sign``
> + - (empty) : for 32 or 64 bit sizes
> + - ``u`` : unsigned
> + - ``s`` : signed
> +
> +``size``
> + - ``b`` : 8 bits
> + - ``w`` : 16 bits
> + - ``l`` : 32 bits
> + - ``q`` : 64 bits
> +
> +Regexes for git grep:
> + - ``\<cpu_ld[us]\?[bwlq]_code\>``
> +
> +``translator_ld*``
> +~~~~~~~~~~~~~~~~~~
> +
> +These functions are a wrapper for ``cpu_ld*_code`` which also perform
> +any actions required by any tracing plugins.  They are only to be
> +called during the translator callback ``translate_insn``.
> +
> +There is a set of functions ending in ``_swap`` which, if the parameter
> +is true, returns the value in the endianness that is the reverse of
> +the guest native endianness, as determined by ``TARGET_WORDS_BIGENDIAN``.
> +
> +Function names follow the pattern:
> +
> +load: ``translator_ld{sign}{size}(env, ptr)``
> +
> +swap: ``translator_ld{sign}{size}_swap(env, ptr, swap)``
> +
> +``sign``
> + - (empty) : for 32 or 64 bit sizes
> + - ``u`` : unsigned
> + - ``s`` : signed
> +
> +``size``
> + - ``b`` : 8 bits
> + - ``w`` : 16 bits
> + - ``l`` : 32 bits
> + - ``q`` : 64 bits
> +
> +Regexes for git grep
> + - ``\<translator_ld[us]\?[bwlq]\(_swap\)\?\>``
> +
> +``helper_*_{ld,st}*_mmu``
> +~~~~~~~~~~~~~~~~~~~~~~~~~
>  
>  These functions are intended primarily to be called by the code
>  generated by the TCG backend. They may also be called by target
> -CPU helper function code. Like the ``cpu_{ld,st}_*_ra`` functions
> -they perform accesses by guest virtual address; the difference is
> -that these functions allow you to specify an ``opindex`` parameter
> -which encodes (among other things) the mmu index to use for the
> -access. This is necessary if your helper needs to make an access
> -via a specific mmu index (for instance, an "always as non-privileged"
> -access) rather than using the default mmu index for the current state
> -of the guest CPU.
> +CPU helper function code. Like the ``cpu_{ld,st}_mmuidx_ra`` functions
> +they perform accesses by guest virtual address, with a given ``mmuidx``.
>  
> -The ``opindex`` parameter should be created by calling ``make_memop_idx()``.
> +These functions specify an ``opindex`` parameter which encodes
> +(among other things) the mmu index to use for the access.  This parameter
> +should be created by calling ``make_memop_idx()``.
>  
>  The ``retaddr`` parameter should be the result of GETPC() called directly
>  from the top level HELPER(foo) function (or 0 if no guest CPU state
> @@ -166,8 +264,9 @@ unwinding is required).
>  
>  **TODO** The names of these functions are a bit odd for historical
>  reasons because they were originally expected to be called only from
> -within generated code. We should rename them to bring them
> -more in line with the other memory access functions.
> +within generated code. We should rename them to bring them more in
> +line with the other memory access functions. The explicit endianness
> +is the only feature they have beyond ``*_mmuidx_ra``.
>  
>  load: ``helper_{endian}_ld{sign}{size}_mmu(env, addr, opindex, retaddr)``


-- 
Alex Bennée