Hi,
I found that, in version qemu-0.9.1 QEMU using original way
to calculate guest physical address
First qemu needs to translate the guest virtual address to guest physical
address.
Then qemu needs to find the PhysPageDesc entry in table l1_phys_map and
get the phys_offset.
At last qemu should add phys_offset to phys_ram_base to get the host
virtual address.
-----------------------------------------------------------------------
softmmu_template.h
DATA_TYPE REGPARM(1) glue(glue(__ld, SUFFIX), MMUSUFFIX)(target_ulong
addr,
int mmu_idx)
{
DATA_TYPE res;
int index;
target_ulong tlb_addr;
target_phys_addr_t physaddr;
void *retaddr;
/* test if there is match for unaligned or IO access */
/* XXX: could done more in memory macro in a non portable way */
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
redo:
tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
if ((addr & TARGET_PAGE_MASK) == (tlb_addr & (TARGET_PAGE_MASK |
TLB_INVALID_MASK))) {
physaddr = addr + env->tlb_table[mmu_idx][index].addend;
if (tlb_addr & ~TARGET_PAGE_MASK) {
/* IO access */
if ((addr & (DATA_SIZE - 1)) != 0)
goto do_unaligned_access;
res = glue(io_read, SUFFIX)(physaddr, tlb_addr);
} else if (((addr & ~TARGET_PAGE_MASK) + DATA_SIZE - 1) >=
TARGET_PAGE_SIZE) {
/* slow unaligned access (it spans two pages or IO) */
do_unaligned_access:
retaddr = GETPC();
#ifdef ALIGNED_ONLY
do_unaligned_access(addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
#endif
res = glue(glue(slow_ld, SUFFIX), MMUSUFFIX)(addr,
mmu_idx,
retaddr);
} else {
/* unaligned/aligned access in the same page */
#ifdef ALIGNED_ONLY
if ((addr & (DATA_SIZE - 1)) != 0) {
retaddr = GETPC();
do_unaligned_access(addr, READ_ACCESS_TYPE, mmu_idx,
retaddr);
}
#endif
res = glue(glue(ld, USUFFIX), _raw)((uint8_t
*)(long)physaddr);
}
} else {
/* the page is not in the TLB : fill it */
retaddr = GETPC();
#ifdef ALIGNED_ONLY
if ((addr & (DATA_SIZE - 1)) != 0)
do_unaligned_access(addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
#endif
tlb_fill(addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
goto redo;
}
return res;
}
-----------------------------------------------------------------------------------
---> quest_physical_addr = addr + env->tlb_table[mmu_idx][index].addend;
But from qemu-0.10.0 Qemu uses a softmmu model to speed up this process.
Its main idea is storing the offset of guest virtual address to host
virtual address in a TLB table.
When translating the guest virtual address to host virtual address,
it will search this TLB table firstly. If there is an entry in the table,
then qemu can add this offset to guest virtual address to get the host
virtual address directly.
Otherwise, it needs to search the l1_phys_map table and then fill the
corresponding entry to the TLB table.
The index of this TLB table is bits [19:12] of guest virtual address and
there is no asid field in tlb entry.
This means the TLB table needs to be flushed in process switch!
----------------------------------------------------
softmmu_template.h
DATA_TYPE REGPARM glue(glue(__ld, SUFFIX), MMUSUFFIX)(target_ulong addr,
int mmu_idx)
{
DATA_TYPE res;
int index;
target_ulong tlb_addr;
target_phys_addr_t addend;
void *retaddr;
/* test if there is match for unaligned or IO access */
/* XXX: could done more in memory macro in a non portable way */
index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
redo:
tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
if ((addr & TARGET_PAGE_MASK) == (tlb_addr & (TARGET_PAGE_MASK |
TLB_INVALID_MASK))) {
if (tlb_addr & ~TARGET_PAGE_MASK) {
/* IO access */
if ((addr & (DATA_SIZE - 1)) != 0)
goto do_unaligned_access;
retaddr = GETPC();
addend = env->iotlb[mmu_idx][index];
res = glue(io_read, SUFFIX)(addend, addr, retaddr);
} else if (((addr & ~TARGET_PAGE_MASK) + DATA_SIZE - 1) >=
TARGET_PAGE_SIZE) {
/* slow unaligned access (it spans two pages or IO) */
do_unaligned_access:
retaddr = GETPC();
#ifdef ALIGNED_ONLY
do_unaligned_access(addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
#endif
res = glue(glue(slow_ld, SUFFIX), MMUSUFFIX)(addr,
mmu_idx,
retaddr);
} else {
/* unaligned/aligned access in the same page */
#ifdef ALIGNED_ONLY
if ((addr & (DATA_SIZE - 1)) != 0) {
retaddr = GETPC();
do_unaligned_access(addr, READ_ACCESS_TYPE, mmu_idx,
retaddr);
}
#endif
addend = env->tlb_table[mmu_idx][index].addend;
res = glue(glue(ld, USUFFIX), _raw)((uint8_t
*)(long)(addr+addend));
}
} else {
/* the page is not in the TLB : fill it */
retaddr = GETPC();
#ifdef ALIGNED_ONLY
if ((addr & (DATA_SIZE - 1)) != 0)
do_unaligned_access(addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
#endif
tlb_fill(addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
goto redo;
}
return res;
}
-----------------------------------------------------------
----> host_virtual_address = addr + env->tlb_table[mmu_idx][index].addend;
So , guest physical address equal host virtual address
I dont think so..
Anybody explain it for me? Which is right or wrong?
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