diff options
| -rw-r--r-- | target-arm/helper.c | 20 |
1 files changed, 11 insertions, 9 deletions
diff --git a/target-arm/helper.c b/target-arm/helper.c index c47487a0af..b74d348a3b 100644 --- a/target-arm/helper.c +++ b/target-arm/helper.c @@ -4545,16 +4545,18 @@ static int get_phys_addr_lpae(CPUARMState *env, target_ulong address, goto do_fault; } - /* The starting level depends on the virtual address size which can be - * up to 48-bits and the translation granule size. + /* The starting level depends on the virtual address size (which can be + * up to 48 bits) and the translation granule size. It indicates the number + * of strides (granule_sz bits at a time) needed to consume the bits + * of the input address. In the pseudocode this is: + * level = 4 - RoundUp((inputsize - grainsize) / stride) + * where their 'inputsize' is our 'va_size - tsz', 'grainsize' is + * our 'granule_sz + 3' and 'stride' is our 'granule_sz'. + * Applying the usual "rounded up m/n is (m+n-1)/n" and simplifying: + * = 4 - (va_size - tsz - granule_sz - 3 + granule_sz - 1) / granule_sz + * = 4 - (va_size - tsz - 4) / granule_sz; */ - if ((va_size - tsz) > (granule_sz * 4 + 3)) { - level = 0; - } else if ((va_size - tsz) > (granule_sz * 3 + 3)) { - level = 1; - } else { - level = 2; - } + level = 4 - (va_size - tsz - 4) / granule_sz; /* Clear the vaddr bits which aren't part of the within-region address, * so that we don't have to special case things when calculating the |