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Re: [Qemu-devel] [PATCH v7 5/7] memory: make mmio dispatch able to be ou
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v7 5/7] memory: make mmio dispatch able to be out of biglock |
Date: |
Mon, 06 May 2013 13:30:55 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 |
Il 06/05/2013 13:25, Jan Kiszka ha scritto:
> On 2013-05-06 13:21, Paolo Bonzini wrote:
>> Il 25/11/2012 03:03, Liu Ping Fan ha scritto:
>>> @@ -3550,12 +3668,11 @@ void *address_space_map(AddressSpace *as,
>>> target_phys_addr_t *plen,
>>> bool is_write)
>>> {
>>> - AddressSpaceDispatch *d = as->dispatch;
>>> target_phys_addr_t len = *plen;
>>> target_phys_addr_t todo = 0;
>>> int l;
>>> target_phys_addr_t page;
>>> - MemoryRegionSection *section;
>>> + MemoryRegionSection *section, mr_obj;
>>> ram_addr_t raddr = RAM_ADDR_MAX;
>>> ram_addr_t rlen;
>>> void *ret;
>>> @@ -3565,7 +3682,8 @@ void *address_space_map(AddressSpace *as,
>>> l = (page + TARGET_PAGE_SIZE) - addr;
>>> if (l > len)
>>> l = len;
>>> - section = phys_page_find(d, page >> TARGET_PAGE_BITS);
>>> + address_space_section_lookup_ref(as, page >> TARGET_PAGE_BITS,
>>> &mr_obj);
>>> + section = &mr_obj;
>>>
>>> if (!(memory_region_is_ram(section->mr) && !section->readonly)) {
>>> if (todo || bounce.buffer) {
>>> @@ -3579,6 +3697,7 @@ void *address_space_map(AddressSpace *as,
>>> }
>>>
>>> *plen = l;
>>> + memory_region_section_unref(&mr_obj);
>>> return bounce.buffer;
>>> }
>>> if (!todo) {
>>> @@ -3589,6 +3708,7 @@ void *address_space_map(AddressSpace *as,
>>> len -= l;
>>> addr += l;
>>> todo += l;
>>> + memory_region_section_unref(&mr_obj);
>>> }
>>> rlen = todo;
>>> ret = qemu_ram_ptr_length(raddr, &rlen);
>>
>> I think this unref is wrong. You need to delay it to the
>> address_space_unmap, and this in turns requires changing the signature
>> of address_space_map.
>
> Can't RAMBlock hold a reference to the associated region? Then this
> could be retrieved on unmap without bothering the caller.
Right you are. :) In fact, RAMBlock already does have block->mr.
Paolo