Hi Stefano,
Sorry for the late answer.
On 13/05/2021 23:44, Stefano Stabellini wrote:
On Wed, 12 May 2021, Julien Grall wrote:
Hi Stefano,
On 12/05/2021 22:30, Stefano Stabellini wrote:
On Wed, 12 May 2021, Julien Grall wrote:
+#define LPAE_SHIFT LPAE_SHIFT_GS(PAGE_SHIFT)
+#define LPAE_ENTRIES LPAE_ENTRIES_GS(PAGE_SHIFT)
+#define LPAE_ENTRY_MASK LPAE_ENTRY_MASK_GS(PAGE_SHIFT)
+#define LEVEL_SHIFT(lvl) LEVEL_SHIFT_GS(PAGE_SHIFT, lvl)
+#define LEVEL_ORDER(lvl) LEVEL_ORDER_GS(PAGE_SHIFT, lvl)
+#define LEVEL_SIZE(lvl) LEVEL_SIZE_GS(PAGE_SHIFT, lvl)
+#define LEVEL_MASK(lvl) (~(LEVEL_SIZE(lvl) - 1))
I would avoid adding these 4 macros. It would be OK if they were just
used within this file but lpae.h is a header: they could end up be used
anywhere in the xen/ code and they have a very generic name. My
suggestion would be to skip them and just do:
Those macros will be used in follow-up patches. They are pretty useful to
avoid introduce static array with the different information for each
level.
Would prefix them with XEN_ be better?
Maybe. The concern I have is that there are multiple page granularities
(4kb, 16kb, etc) and multiple page sizes (4kb, 2mb, etc). If I just see
LEVEL_ORDER it is not immediately obvious what granularity and what size
we are talking about.
I am a bit puzzled with your answer. AFAIU, you are happy with the existing
macros (THIRD_*, SECOND_*) but not with the new macros.
In reality, there is no difference because THIRD_* doesn't tell you the exact
size but only "this is a level 3 mapping".
So can you clarify what you are after? IOW is it reworking the current naming
scheme?
You are right -- there is no real difference between THIRD_*, SECOND_*
and LEVEL_*.
The original reason for my comments is that I hadn't read the following
patches, and the definition of LEVEL_* macros is simple, they could be
open coded. It looked like they were only going to be used to make the
definition of THIRD_*, SECOND_* a bit easier. So, at first, I was
wondering if they were needed at all.
Secondly, I realized that they were going to be used in *.c files by
other patches. That's why they are there. But I started thinking whether
we should find a way to make it a bit clearer that they are for Xen
pages, currently at 4KB granularity. THIRD_*, SECOND_*, etc. are already
generic names which don't convey the granularity or whether they are Xen
pages at all. But LEVEL_* seem even more generic.
As I mentioned, I don't have any good suggestions for changes to make
here, so unless you can come up with a good idea let's keep it as is.
I am thinking to use the following naming (diff on top of this patch):
-#define LPAE_SHIFT LPAE_SHIFT_GS(PAGE_SHIFT)
-#define LPAE_ENTRIES LPAE_ENTRIES_GS(PAGE_SHIFT)
-#define LPAE_ENTRY_MASK LPAE_ENTRY_MASK_GS(PAGE_SHIFT)
+#define XEN_PT_SHIFT LPAE_SHIFT_GS(PAGE_SHIFT)
+#define XEN_PT_ENTRIES LPAE_ENTRIES_GS(PAGE_SHIFT)
+#define XEN_PT_ENTRY_MASK LPAE_ENTRY_MASK_GS(PAGE_SHIFT)
-#define LEVEL_SHIFT(lvl) LEVEL_SHIFT_GS(PAGE_SHIFT, lvl)
-#define LEVEL_ORDER(lvl) LEVEL_ORDER_GS(PAGE_SHIFT, lvl)
-#define LEVEL_SIZE(lvl) LEVEL_SIZE_GS(PAGE_SHIFT, lvl)
-#define LEVEL_MASK(lvl) (~(LEVEL_SIZE(lvl) - 1))
+#define XEN_PT_LEVEL_SHIFT(lvl) LEVEL_SHIFT_GS(PAGE_SHIFT, lvl)
+#define XEN_PT_LEVEL_ORDER(lvl) LEVEL_ORDER_GS(PAGE_SHIFT, lvl)
+#define XEN_PT_LEVEL_SIZE(lvl) LEVEL_SIZE_GS(PAGE_SHIFT, lvl)
+#define XEN_PT_LEVEL_MASK(lvl) (~(LEVEL_SIZE(lvl) - 1))
/* Convenience aliases */
-#define THIRD_SHIFT LEVEL_SHIFT(3)
-#define THIRD_ORDER LEVEL_ORDER(3)
-#define THIRD_SIZE LEVEL_SIZE(3)
-#define THIRD_MASK LEVEL_MASK(3)
-
-#define SECOND_SHIFT LEVEL_SHIFT(2)
-#define SECOND_ORDER LEVEL_ORDER(2)
-#define SECOND_SIZE LEVEL_SIZE(2)
-#define SECOND_MASK LEVEL_MASK(2)
-
-#define FIRST_SHIFT LEVEL_SHIFT(1)
-#define FIRST_ORDER LEVEL_ORDER(1)
-#define FIRST_SIZE LEVEL_SIZE(1)
-#define FIRST_MASK LEVEL_MASK(1)
-
-#define ZEROETH_SHIFT LEVEL_SHIFT(0)
-#define ZEROETH_ORDER LEVEL_ORDER(0)
-#define ZEROETH_SIZE LEVEL_SIZE(0)
-#define ZEROETH_MASK LEVEL_MASK(0)
+#define THIRD_SHIFT XEN_PT_LEVEL_SHIFT(3)
+#define THIRD_ORDER XEN_PT_LEVEL_ORDER(3)
+#define THIRD_SIZE XEN_PT_LEVEL_SIZE(3)
+#define THIRD_MASK XEN_PT_LEVEL_MASK(3)
+
+#define SECOND_SHIFT XEN_PT_LEVEL_SHIFT(2)
+#define SECOND_ORDER XEN_PT_LEVEL_ORDER(2)
+#define SECOND_SIZE XEN_PT_LEVEL_SIZE(2)
+#define SECOND_MASK XEN_PT_LEVEL_MASK(2)
+
+#define FIRST_SHIFT XEN_PT_LEVEL_SHIFT(1)
+#define FIRST_ORDER XEN_PT_LEVEL_ORDER(1)
+#define FIRST_SIZE XEN_PT_LEVEL_SIZE(1)
+#define FIRST_MASK XEN_PT_LEVEL_MASK(1)
+
+#define ZEROETH_SHIFT XEN_PT_LEVEL_SHIFT(0)
+#define ZEROETH_ORDER XEN_PT_LEVEL_ORDER(0)
+#define ZEROETH_SIZE XEN_PT_LEVEL_SIZE(0)
+#define ZEROETH_MASK XEN_PT_LEVEL_MASK(0)
I don't plan to modify the nameing for ZEROETH*, FIRST*, SECOND*, THIRD*.
Let me know if you prefer it over the currrent naming.
Cheers,
--
Julien Grall
