@@ -127,6 +127,15 @@ QEMU_BUILD_BUG_ON(sizeof(CPUTLBEntry) != (1 << CPU_TLB_ENTRY_BITS));
* structs into one.)
*/
typedef struct CPUIOTLBEntry {
+ /*
+ * @addr contains:
+ * - in the lower TARGET_PAGE_BITS, a physical section number
+ * - with the lower TARGET_PAGE_BITS masked off, an offset which
+ * must be added to the virtual address to obtain:
+ * + the ramaddr_t of the target RAM (if the physical section
+ * number is PHYS_SECTION_NOTDIRTY or PHYS_SECTION_ROM)
+ * + the offset within the target MemoryRegion (otherwise)
+ */
hwaddr addr;
MemTxAttrs attrs;
} CPUIOTLBEntry;
@@ -664,6 +664,18 @@ void tlb_set_page_with_attrs(CPUState *cpu, target_ulong vaddr,
env->iotlb_v[mmu_idx][vidx] = env->iotlb[mmu_idx][index];
/* refill the tlb */
+ /*
+ * At this point iotlb contains a physical section number in the lower
+ * TARGET_PAGE_BITS, and either
+ * + the ramaddr_t of the page base of the target RAM (if NOTDIRTY or ROM)
+ * + the offset within section->mr of the page base (otherwise)
+ * We subtract the vaddr (which is page aligned and thus won't
+ * disturb the low bits) to give an offset which can be added to the
+ * (non-page-aligned) vaddr of the eventual memory access to get
+ * the MemoryRegion offset for the access. Note that the vaddr we
+ * subtract here is that of the page base, and not the same as the
+ * vaddr we add back in io_readx()/io_writex()/get_page_addr_code().
+ */
env->iotlb[mmu_idx][index].addr = iotlb - vaddr;
env->iotlb[mmu_idx][index].attrs = attrs;
The 'addr' field in the CPUIOTLBEntry struct has a rather non-obvious use; add a comment documenting it (reverse-engineered from what the code that sets it is doing). Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- include/exec/cpu-defs.h | 9 +++++++++ accel/tcg/cputlb.c | 12 ++++++++++++ 2 files changed, 21 insertions(+) -- 2.17.1