Re: [PATCH v4 1/2] accel/tcg: Add probe_access_range_flags interface

[Alistair Francis]

On Thu, Feb 17, 2022 at 1:49 AM Christoph Muellner <cmuellner@linux.com> wrote:
>
> The existing probe_access* functions do not allow to specify the
> access size and a non-faulting behavior at the same time.
>
> This is resolved by adding a generalization of probe_access_flags()
> that takes an additional size parameter.
>
> The semantics is basically the same as probe_access_flags(),
> but instead of assuming an access to any byte of the addressed
> page, we can restrict to access to a specific area, like
> probe_access() allows.
>
> Signed-off-by: Christoph Muellner <cmuellner@linux.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  accel/tcg/cputlb.c      | 17 +++++++++++++----
>  accel/tcg/user-exec.c   | 15 ++++++++++++---
>  include/exec/exec-all.h | 24 ++++++++++++++++++++++++
>  3 files changed, 49 insertions(+), 7 deletions(-)
>
> diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
> index 5e0d0eebc3..b4f0eb20b0 100644
> --- a/accel/tcg/cputlb.c
> +++ b/accel/tcg/cputlb.c
> @@ -1624,13 +1624,14 @@ static int probe_access_internal(CPUArchState *env, 
> target_ulong addr,
>      return flags;
>  }
>
> -int probe_access_flags(CPUArchState *env, target_ulong addr,
> -                       MMUAccessType access_type, int mmu_idx,
> -                       bool nonfault, void **phost, uintptr_t retaddr)
> +int probe_access_range_flags(CPUArchState *env, target_ulong addr,
> +                             int size, MMUAccessType access_type,
> +                             int mmu_idx, bool nonfault, void **phost,
> +                             uintptr_t retaddr)
>  {
>      int flags;
>
> -    flags = probe_access_internal(env, addr, 0, access_type, mmu_idx,
> +    flags = probe_access_internal(env, addr, size, access_type, mmu_idx,
>                                    nonfault, phost, retaddr);
>
>      /* Handle clean RAM pages.  */
> @@ -1645,6 +1646,14 @@ int probe_access_flags(CPUArchState *env, target_ulong 
> addr,
>      return flags;
>  }
>
> +int probe_access_flags(CPUArchState *env, target_ulong addr,
> +                       MMUAccessType access_type, int mmu_idx,
> +                       bool nonfault, void **phost, uintptr_t retaddr)
> +{
> +    return probe_access_range_flags(env, addr, 0, access_type, mmu_idx,
> +                                    nonfault, phost, retaddr);
> +}
> +
>  void *probe_access(CPUArchState *env, target_ulong addr, int size,
>                     MMUAccessType access_type, int mmu_idx, uintptr_t retaddr)
>  {
> diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
> index 6f5d4933f0..0dbc345e63 100644
> --- a/accel/tcg/user-exec.c
> +++ b/accel/tcg/user-exec.c
> @@ -176,9 +176,10 @@ static int probe_access_internal(CPUArchState *env, 
> target_ulong addr,
>      cpu_loop_exit_sigsegv(env_cpu(env), addr, access_type, maperr, ra);
>  }
>
> -int probe_access_flags(CPUArchState *env, target_ulong addr,
> -                       MMUAccessType access_type, int mmu_idx,
> -                       bool nonfault, void **phost, uintptr_t ra)
> +int probe_access_range_flags(CPUArchState *env, target_ulong addr,
> +                             int size, MMUAccessType access_type,
> +                             int mmu_idx, bool nonfault, void **phost,
> +                             uintptr_t ra)
>  {
>      int flags;
>
> @@ -187,6 +188,14 @@ int probe_access_flags(CPUArchState *env, target_ulong 
> addr,
>      return flags;
>  }
>
> +int probe_access_flags(CPUArchState *env, target_ulong addr,
> +                       MMUAccessType access_type, int mmu_idx,
> +                       bool nonfault, void **phost, uintptr_t ra)
> +{
> +    return probe_access_range_flags(env, addr, 0, access_type, mmu_idx,
> +                                    nonfault, phost, ra);
> +}
> +
>  void *probe_access(CPUArchState *env, target_ulong addr, int size,
>                     MMUAccessType access_type, int mmu_idx, uintptr_t ra)
>  {
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 35d8e93976..0d06b45c62 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -441,6 +441,30 @@ static inline void *probe_read(CPUArchState *env, 
> target_ulong addr, int size,
>      return probe_access(env, addr, size, MMU_DATA_LOAD, mmu_idx, retaddr);
>  }
>
> +/**
> + * probe_access_range_flags:
> + * @env: CPUArchState
> + * @addr: guest virtual address to look up
> + * @size: size of the access
> + * @access_type: read, write or execute permission
> + * @mmu_idx: MMU index to use for lookup
> + * @nonfault: suppress the fault
> + * @phost: return value for host address
> + * @retaddr: return address for unwinding
> + *
> + * Similar to probe_access, loosely returning the TLB_FLAGS_MASK for
> + * the access range, and storing the host address for RAM in @phost.
> + *
> + * If @nonfault is set, do not raise an exception but return 
> TLB_INVALID_MASK.
> + * Do not handle watchpoints, but include TLB_WATCHPOINT in the returned 
> flags.
> + * Do handle clean pages, so exclude TLB_NOTDIRY from the returned flags.
> + * For simplicity, all "mmio-like" flags are folded to TLB_MMIO.
> + */
> +int probe_access_range_flags(CPUArchState *env, target_ulong addr,
> +                             int size, MMUAccessType access_type,
> +                             int mmu_idx, bool nonfault, void **phost,
> +                             uintptr_t retaddr);
> +
>  /**
>   * probe_access_flags:
>   * @env: CPUArchState
> --
> 2.35.1
>
>