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Date: Thu, 18 Jun 2015 17:46:40 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH V3] Use atomic cmpxchg to atomically
 check the exclusive value in a STREX
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To: fred.konrad@greensocs.com, qemu-devel@nongnu.org, mttcg@greensocs.com
Cc: mark.burton@greensocs.com, peter.maydell@linaro.org, alex.bennee@linaro.org, agraf@suse.de, guillaume.delbergue@greensocs.com



On 18/06/2015 17:44, fred.konrad@greensocs.com wrote:
> +    hwaddr len = 8 << size;

Should be 1 << size, and likewise below in the "if".

Paolo

> +    hwaddr paddr;
> +    target_ulong page_size;
> +    int prot;
> +
> +    arm_exclusive_lock();
> +
> +    if (env->exclusive_addr != addr) {
> +        arm_exclusive_unlock();
> +        return 1;
> +    }
> +
> +    if (arm_get_phys_addr(env, addr, 1, &paddr, &prot, &page_size) != 0) {
> +        tlb_fill(ENV_GET_CPU(env), addr, MMU_DATA_STORE, cpu_mmu_index(env),
> +                 retaddr);
> +        if  (arm_get_phys_addr(env, addr, 1, &paddr, &prot, &page_size) != 0) {
> +            arm_exclusive_unlock();
> +            return 1;
> +        }
> +    }
> +
> +    switch (size) {
> +    case 0:
> +    {
> +        uint8_t oldval, *p;
> +        p = address_space_map(cs->as, paddr, &len, true);
> +        if (len == 8 << size) {
> +            oldval = (uint8_t)env->exclusive_val;
> +            result = (atomic_cmpxchg(p, oldval, (uint8_t)newval) == oldval);
> +        }
> +        address_space_unmap(cs->as, p, len, true, result ? 8 : 0);
> +    }
> +    break;
> +    case 1:
> +    {
> +        uint16_t oldval, *p;
> +        p = address_space_map(cs->as, paddr, &len, true);
> +        if (len == 8 << size) {
> +            oldval = (uint16_t)env->exclusive_val;
> +            result = (atomic_cmpxchg(p, oldval, (uint16_t)newval) == oldval);
> +        }
> +        address_space_unmap(cs->as, p, len, true, result ? 8 : 0);
> +    }
> +    break;
> +    case 2:
> +    {
> +        uint32_t oldval, *p;
> +        p = address_space_map(cs->as, paddr, &len, true);
> +        if (len == 8 << size) {
> +            oldval = (uint32_t)env->exclusive_val;
> +            result = (atomic_cmpxchg(p, oldval, (uint32_t)newval) == oldval);
> +        }
> +        address_space_unmap(cs->as, p, len, true, result ? 8 : 0);
> +    }
> +    break;
> +    case 3:
> +    {
> +        uint64_t oldval, *p;
> +        p = address_space_map(cs->as, paddr, &len, true);
> +        if (len == 8 << size) {
> +            oldval = (uint64_t)env->exclusive_val;
> +            result = (atomic_cmpxchg(p, oldval, (uint64_t)newval) == oldval);
> +        }
> +        address_space_unmap(cs->as, p, len, true, result ? 8 : 0);
> +    }
> +    break;
> +    default:
> +        abort();
> +    break;