On Mon, Sep 15, 2025 at 12:51:52PM -0300, Jason Gunthorpe wrote:
On Tue, Sep 09, 2025 at 08:40:28PM -0700, Nicolin Chen wrote: How aboutL:
- level
Level 0 is always a table of only leaves with no futher table pointers.Increasing levels increase the size of the table items. The leastsignificant VA bits used to index page tables are used to index the Level0 table.
Yea, this is clearer.
- item
A single position in a table
- entry
A single logical element in a table. If contiguous pages are not
supported then item and entry are the same thing, otherwise entry refers
to the all the items that comprise a single contiguous translation.So, an "entry" is a group of "items" if contiguous pages (huge page?) are supported.
Yes
Then, the "entry" sounds like a physical (v.s. "logical") table entry, e.g. a PTE that we usually say?
I choose entry because it is related to PTE and in most cases you want to work on the entries. The replication of entry to item is somewhat hidden.
From a HW perspective the TLB should be loading entries.
In that case, "entry" should be a single "physical" element v.s. "logical", right? Because that's what HW/TLB physically loads.
+#if !IS_ENABLED(CONFIG_GENERIC_ATOMIC64) +static inline bool pt_table_install64(struct pt_state *pts, u64 table_entry) +{
- u64 *entryp = pt_cur_table(pts, u64) + pts->index;
- u64 old_entry = pts->entry;
- bool ret;
- /*
* Ensure the zero'd table content itself is visible before its PTE can* be. release is a NOP on !SMP, but the HW is still doing an acquire.*/- if (!IS_ENABLED(CONFIG_SMP))
dma_wmb();Mind elaborating why SMP doesn't need this?
The command says the "relase is a NOP" it means this:
ret = try_cmpxchg64_release(entryp, &old_entry, table_entry);
On SMP release does an actual release, on UP it doesn't have a barrier.
I see. I found that on !SMP, smp_mb() is barrier() v.s. mb(). I suppose that differs between a compiler one and hardware one.
Thanks Nicolin