Re: Question about CPUTLBEntry

[Richard Henderson]

On 11/30/22 14:50, Nada Lachtar wrote:
> Hello,
>
>
> I’m trying to understand the structure of TLB in QEMU/tcg, in order to extract 
> the physical address from the CPUTLBEntry. Would this be possible without 
> having the virtual address and use tlb_lookup? For example, I would like to 
> read all the physical addresses that are recorded in the TLB table without the 
> need for a virtual address to translate the entry.
>
> I would appreciate your help in directing me to what functions/structures to 
> use to achieve this.

The virtual address of the CPUTLBEntry is recorded as the page-address bits in each of the 
three comparators: addr_read, addr_write, addr_code.  This is documented in the comment 
right there with CPUTLBEntry (TARGET_LONG_BITS to TARGET_PAGE_BITS).

Bits below TARGET_PAGE_BITS are TLB flags, e.g. TLB_MMIO.

If TLB_INVALID_MASK is set in addr_{read,write,code}, the entry is not 
readable/writable/executable.  If TLB_INVALID_MASK is set in all three, the entry is unused.

If CPUTLBEntry is valid, there is also a CPUTLBEntryFull structure in parallel, which 
contains (among other things), CPUTLBEntryFull.phys_addr, containing the cpu-side physical 
address for the address space given by CPUTLBEntryFull.attrs.


r~