Re: [Qemu-devel] [PATCH-for-4.2 v1 3/9] s390x/mmu: DAT translation rewrite

[Thomas Huth]

On 8/5/19 5:29 PM, David Hildenbrand wrote:
> Let's rewrite the DAT translation in a non-recursive way, similar to
> arch/s390/kvm/gaccess.c:guest_translate() in KVM. This makes the
> code much easier to read, compare and maintain.
> 
> Use better names for the region/section/page table entries and for the
> macros to extract relevant parts from virtual address. Introduce defines
> for all defined bits, this will come in handy soon.
> 
> All access exceptions now directly go via trigger_access_exception(),
> at a central point. DAT protection checks are performed at a central
> place.
> 
> Also, we now catch and indicate invalid addresses of page tables. All
> table entries are accessed via read_table_entry().
> 
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  target/s390x/cpu.h        |  77 +++++---
>  target/s390x/mem_helper.c |  13 +-
>  target/s390x/mmu_helper.c | 360 +++++++++++++++++---------------------
>  3 files changed, 229 insertions(+), 221 deletions(-)
> 
> diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> index c34992bb2e..1ff14250bd 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -554,26 +554,63 @@ QEMU_BUILD_BUG_ON(sizeof(SysIB) != 4096);
>  #define ASCE_TYPE_SEGMENT     0x00        /* segment table type              
>  */
>  #define ASCE_TABLE_LENGTH     0x03        /* region table length             
>  */
>  
> -#define REGION_ENTRY_ORIGIN   (~0xfffULL) /* region/segment table origin    
> */
> -#define REGION_ENTRY_RO       0x200       /* region/segment protection bit  
> */
> -#define REGION_ENTRY_TF       0xc0        /* region/segment table offset    
> */
> -#define REGION_ENTRY_INV      0x20        /* invalid region table entry     
> */
> -#define REGION_ENTRY_TYPE_MASK 0x0c       /* region/segment table type mask 
> */
> -#define REGION_ENTRY_TYPE_R1  0x0c        /* region first table type        
> */
> -#define REGION_ENTRY_TYPE_R2  0x08        /* region second table type       
> */
> -#define REGION_ENTRY_TYPE_R3  0x04        /* region third table type        
> */
> -#define REGION_ENTRY_LENGTH   0x03        /* region third length            
> */
> -
> -#define SEGMENT_ENTRY_ORIGIN  (~0x7ffULL) /* segment table origin        */
> -#define SEGMENT_ENTRY_FC      0x400       /* format control              */
> -#define SEGMENT_ENTRY_RO      0x200       /* page protection bit         */
> -#define SEGMENT_ENTRY_INV     0x20        /* invalid segment table entry */
> -
> -#define VADDR_PX              0xff000     /* page index bits   */
> -
> -#define PAGE_RO               0x200       /* HW read-only bit  */
> -#define PAGE_INVALID          0x400       /* HW invalid bit    */
> -#define PAGE_RES0             0x800       /* bit must be zero  */
> +#define REGION_ENTRY_ORIGIN         0xfffffffffffff000ULL
> +#define REGION_ENTRY_P              0x0000000000000200ULL
> +#define REGION_ENTRY_TF             0x00000000000000c0ULL
> +#define REGION_ENTRY_I              0x0000000000000020ULL
> +#define REGION_ENTRY_TT             0x000000000000000cULL
> +#define REGION_ENTRY_TL             0x0000000000000003ULL
> +
> +#define REGION_ENTRY_TT_REGION1     0x000000000000000cULL
> +#define REGION_ENTRY_TT_REGION2     0x0000000000000008ULL
> +#define REGION_ENTRY_TT_REGION3     0x0000000000000004ULL
> +
> +#define REGION3_ENTRY_RFAA          0xffffffff80000000ULL
> +#define REGION3_ENTRY_AV            0x0000000000010000ULL
> +#define REGION3_ENTRY_ACC           0x000000000000f000ULL
> +#define REGION3_ENTRY_F             0x0000000000000800ULL
> +#define REGION3_ENTRY_FC            0x0000000000000400ULL
> +#define REGION3_ENTRY_IEP           0x0000000000000100ULL
> +#define REGION3_ENTRY_CR            0x0000000000000010ULL
> +
> +#define SEGMENT_ENTRY_ORIGIN        0xfffffffffffff800ULL
> +#define SEGMENT_ENTRY_SFAA          0xfffffffffff80000ULL
> +#define SEGMENT_ENTRY_AV            0x0000000000010000ULL
> +#define SEGMENT_ENTRY_ACC           0x000000000000f000ULL
> +#define SEGMENT_ENTRY_F             0x0000000000000800ULL
> +#define SEGMENT_ENTRY_FC            0x0000000000000400ULL
> +#define SEGMENT_ENTRY_P             0x0000000000000200ULL
> +#define SEGMENT_ENTRY_IEP           0x0000000000000100ULL
> +#define SEGMENT_ENTRY_I             0x0000000000000020ULL
> +#define SEGMENT_ENTRY_CS            0x0000000000000010ULL
> +#define SEGMENT_ENTRY_TT            0x000000000000000cULL
> +
> +#define SEGMENT_ENTRY_TT_REGION1    0x000000000000000cULL
> +#define SEGMENT_ENTRY_TT_REGION2    0x0000000000000008ULL
> +#define SEGMENT_ENTRY_TT_REGION3    0x0000000000000004ULL
> +#define SEGMENT_ENTRY_TT_SEGMENT    0x0000000000000000ULL
> +
> +#define PAGE_ENTRY_0                0x0000000000000800ULL
> +#define PAGE_ENTRY_I                0x0000000000000400ULL
> +#define PAGE_ENTRY_P                0x0000000000000200ULL
> +#define PAGE_ENTRY_IEP              0x0000000000000100ULL
> +
> +#define VADDR_REGION1_TX_MASK       0xffe0000000000000ULL
> +#define VADDR_REGION2_TX_MASK       0x001ffc0000000000ULL
> +#define VADDR_REGION3_TX_MASK       0x000003ff80000000ULL
> +#define VADDR_SEGMENT_TX_MASK       0x000000007ff00000ULL
> +#define VADDR_PAGE_TX_MASK          0x00000000000ff000ULL
> +
> +#define VADDR_REGION1_TX(vaddr)     (((vaddr) & VADDR_REGION1_TX_MASK) >> 53)
> +#define VADDR_REGION2_TX(vaddr)     (((vaddr) & VADDR_REGION2_TX_MASK) >> 42)
> +#define VADDR_REGION3_TX(vaddr)     (((vaddr) & VADDR_REGION3_TX_MASK) >> 31)
> +#define VADDR_SEGMENT_TX(vaddr)     (((vaddr) & VADDR_SEGMENT_TX_MASK) >> 20)
> +#define VADDR_PAGE_TX(vaddr)        (((vaddr) & VADDR_PAGE_TX_MASK) >> 12)
> +
> +#define VADDR_REGION1_TL(vaddr)     (((vaddr) & 0xc000000000000000ULL) >> 62)
> +#define VADDR_REGION2_TL(vaddr)     (((vaddr) & 0x0018000000000000ULL) >> 51)
> +#define VADDR_REGION3_TL(vaddr)     (((vaddr) & 0x0000030000000000ULL) >> 40)
> +#define VADDR_SEGMENT_TL(vaddr)     (((vaddr) & 0x0000000060000000ULL) >> 29)

Ugh, this patch is quite big, and you're doing multiple things at once
here, e.g. renaming macros from PAGE_INVALID to PAGE_ENTRY_I ... could
you maybe split this up in multiple patches instead? Also, is this
complete rewrite really necessary, just to match your personal taste? I
think it would be easier to review if you'd just fix the current code
instead if necessary...

 Thomas