On 09/14/2016 04:52 PM, Paolo Bonzini wrote:
On 14/09/2016 23:47, Brijesh Singh wrote:
On 09/14/2016 04:00 PM, Paolo Bonzini wrote:
On 14/09/2016 22:59, Brijesh Singh wrote:
I will look into hooking up the callback into ROM read/write ops. I was
thinking about adding a new argument in
cpu_physical_memory_write_rom_internal()
void cpu_physical_memory_write_rom(AddressSpace *as, hwaddr addr,
const uint8_t *buf, int len,
WriteCB *cb)
{
....
ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
if (cb)
cb(ptr, buf, len)
else
memcpy(ptr, buf, len)
....
}
In case of SEV, we pass a CB function pointer which calls SEV API's to
encrypt memory. Does this make sense?
I think a global as you have it in this series is just fine---just don't
hook it into address_space_read and address_space_write.
Actually in SEV RAM callback I check the Attrs, if attr.sev_debug flag
set then use SEV debug command otherwise default to memcpy so that DMA
and everything else works. I guest the main reason why i choose to hook
this up in address_space_read/write was that I found that
address_space_write and address_space_read is used in debug path. e.g
cpu_memory_rw_debug
address_space_rw
address_space_write/read
Right, but if you change this to a ROM hook only, cpu_memory_rw_debug
will go through cpu_physical_memory_write_rom instead. This will invoke
the hook properly, won't it? It will break -kernel unless fw_cfg DMA is
disabled, of course.
maybe I am missing something.
here is what I see:
int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
uint8_t *buf, int len, int is_write)
{
............
if (is_write)
cpu_physical_memory_write_rom_internal()
else
address_space_rw()
.....
}
So looking at code, i have impression that write will go through the
cpu_physical_memory_write_rom but the read will still go through
address_space_rw which will eventually invoke address_space_read.
Also when user tries to read or write to a physical address through qemu
monitor then it will invoke cpu_physical_memory_rw which will eventually
use address_space_write and address_space_read to read/write the guest
memory.
