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Re: [Qemu-devel] [PATCH v2] cpu_defs: Simplify CPUTLB padding logic
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2] cpu_defs: Simplify CPUTLB padding logic |
Date: |
Thu, 9 Jul 2015 17:04:08 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 |
On 09/07/2015 05:26, Peter Crosthwaite wrote:
> There was a complicated subtractive arithmetic for determining the
> padding on the CPUTLBEntry structure. Simplify this with a union.
>
> Signed-off-by: Peter Crosthwaite <address@hidden>
> ---
> Changed since v1:
> Remove un-needed anonymous union (Paolo review)
> ---
> include/exec/cpu-defs.h | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h
> index 98b9cff..c6828cc 100644
> --- a/include/exec/cpu-defs.h
> +++ b/include/exec/cpu-defs.h
> @@ -98,24 +98,23 @@ typedef uint64_t target_ulong;
>
> #define CPU_TLB_SIZE (1 << CPU_TLB_BITS)
>
> -typedef struct CPUTLBEntry {
> +typedef union CPUTLBEntry {
> /* bit TARGET_LONG_BITS to TARGET_PAGE_BITS : virtual address
> bit TARGET_PAGE_BITS-1..4 : Nonzero for accesses that should not
> go directly to ram.
> bit 3 : indicates that the entry is invalid
> bit 2..0 : zero
> */
> - target_ulong addr_read;
> - target_ulong addr_write;
> - target_ulong addr_code;
> - /* Addend to virtual address to get host address. IO accesses
> - use the corresponding iotlb value. */
> - uintptr_t addend;
> + struct {
> + target_ulong addr_read;
> + target_ulong addr_write;
> + target_ulong addr_code;
> + /* Addend to virtual address to get host address. IO accesses
> + use the corresponding iotlb value. */
> + uintptr_t addend;
> + };
> /* padding to get a power of two size */
> - uint8_t dummy[(1 << CPU_TLB_ENTRY_BITS) -
> - (sizeof(target_ulong) * 3 +
> - ((-sizeof(target_ulong) * 3) & (sizeof(uintptr_t) - 1)) +
> - sizeof(uintptr_t))];
> + uint8_t dummy[1 << CPU_TLB_ENTRY_BITS];
> } CPUTLBEntry;
>
> QEMU_BUILD_BUG_ON(sizeof(CPUTLBEntry) != (1 << CPU_TLB_ENTRY_BITS));
>
Thanks, queued for 2.5.
Paolo