Re: [Qemu-devel] [PATCH v2] cpu: implementing victim TLB for QEMU system emulated TLB

[Max Filippov]

On Fri, Jan 24, 2014 at 1:29 AM, Xin Tong <address@hidden> wrote:
>>> +/* swap the 2 given TLB entries as well as their corresponding IOTLB */
>>> +inline void swap_tlb(CPUTLBEntry *te, CPUTLBEntry *se, hwaddr *iote,
>>> +                     hwaddr *iose)
>>> +{
>>> +   hwaddr iotmp;
>>> +   CPUTLBEntry t;
>>> +   /* swap iotlb */
>>> +   iotmp = *iote;
>>> +   *iote = *iose;
>>> +   *iose = iotmp;
>>> +   /* swap tlb */
>>> +   memcpy(&t, te, sizeof(CPUTLBEntry));
>>> +   memcpy(te, se, sizeof(CPUTLBEntry));
>>> +   memcpy(se, &t, sizeof(CPUTLBEntry));
>>
>> You could use assignment operator, it works:
>>     t = *te;
>>     *te = *se;
>>     *se = t;
>>
> i see, will fix in patch v3.
>
>> Also all users of this function are inline functions from softmmu_template.h
>> Could this function be a static inline function in that file too?
>
> I am following where tlb_fill and tlb_flush are placed. Also, the
> softmmu_template.h is included more than once, would put the swap_tlb
> in softmmu_template.h result in multiple definitions ?

You're right. Could it be put into a file that is included by softmmu_template.h
and has include guards in it, or could it be turned into macro?

[...]

>>> -        tlb_fill(env, addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
>>> +        /* we are about to do a page table walk. our last hope is the
>>> +         * victim tlb. try to refill from the victim tlb before walking the
>>> +         * page table. */
>>> +        for (vtlb_idx = CPU_VTLB_SIZE; vtlb_idx >= 0; --vtlb_idx) {
>>> +            if (env->tlb_v_table[mmu_idx][vtlb_idx].ADDR_READ
>>
>> Is it ADDR_READ or addr_read, as it is called in other places?
>
> I am following  target_ulong tlb_addr =
> env->tlb_table[mmu_idx][index].ADDR_READ; in the same function. I am
> not sure i get what you mean.

Ok, I see ADDR_READ is a macro defined depending on
SOFTMMU_CODE_ACCESS. I got a bit confused by addr_read used
in other places vs. ADDR_READ used here vs. addr_write used below.
Sorry for the noise.

[...]

>>> -        tlb_fill(env, addr, 1, mmu_idx, retaddr);
>>> +        /* we are about to do a page table walk. our last hope is the
>>> +         * victim tlb. try to refill from the victim tlb before walking the
>>> +         * page table. */
>>> +        for (vtlb_idx = CPU_VTLB_SIZE; vtlb_idx >= 0; --vtlb_idx) {
>>> +            if (env->tlb_v_table[mmu_idx][vtlb_idx].addr_write
>>> +                == (addr & TARGET_PAGE_MASK)) {
>>> +                /* found entry in victim tlb */
>>> +                swap_tlb(&env->tlb_table[mmu_idx][index],
>>> +                         &env->tlb_v_table[mmu_idx][vtlb_idx],
>>> +                         &env->iotlb[mmu_idx][index],
>>> +                         &env->iotlb_v[mmu_idx][vtlb_idx]);
>>> +                break;
>>> +            }
>>> +        }
>>
>> It could be a good inline function too.
>
> One way is to define the victim tlb lookup code in a C function which
> gets called before tlb_fill. but i need the ADDR_READ and addr_write
> macros.

It could be a single macro then, taking ADDR_READ or addr_write
as a parameter.

-- 
Thanks.
-- Max