Svpbmt arch review

* Restore Svpbmt mode names
* Add note about Zicbom

1 files changed, 16 insertions, 12 deletions

diff --git a/src/supervisor.tex b/src/supervisor.tex
index 93c833c..4150084 100644
--- a/src/supervisor.tex
+++ b/src/supervisor.tex
@@ -2273,14 +2273,14 @@ pages.  The encoding for the PBMT bits is captured in Table~\ref{pbmt}.
 
 \begin{table*}[h!]
 \begin{center}
-\begin{tabular}{|r|l|}
+\begin{tabular}{|c|c|l|}
 \hline
-Value  & Requested Memory Attributes \\
+Mode & Value  & Requested Memory Attributes \\
 \hline
-0      & None \\
-1      & Non-cacheable, idempotent, weakly-ordered (RVWMO or RVTSO), main memory \\
-2      & Non-cacheable, non-idempotent, strongly-ordered (I/O ordering), I/O \\
-3      & {\em Reserved for future standard use} \\
+PMA  & 0      & None \\
+NC   & 1      & Non-cacheable, idempotent, weakly-ordered (RVWMO or RVTSO), main memory \\
+IO   & 2      & Non-cacheable, non-idempotent, strongly-ordered (I/O ordering), I/O \\
+$-$  & 3      & {\em Reserved for future standard use} \\
 \hline
 \end{tabular}
 \end{center}
@@ -2298,20 +2298,20 @@ For non-leaf PTEs, bits 62--61 are reserved for future standard use and must be
 cleared by software for forward compatibility.
 
 If the underlying physical memory attribute for a page is main memory and
-the page has PBMT=0 or PBMT=1, or if the underlying physical memory attribute
-for a page is I/O and the page has PBMT=0 or PBMT=2, then accesses to that page
+the page has PBMT=PMA or PBMT=NC, or if the underlying physical memory attribute
+for a page is I/O and the page has PBMT=PMA or PBMT=IO, then accesses to that page
 obey the same memory ordering rules normally applied to accesses to that
 physical page.
 
 If the underlying physical memory attribute for a page is I/O, and the page has
-PBMT=1, then then accesses to that page obey RVWMO.  Accesses to such pages are
+PBMT=NC, then then accesses to that page obey RVWMO.  Accesses to such pages are
 considered main memory rather than I/O for the purposes of FENCE, {\em.aq}, and
 {\em.rl}.
 
 If the underlying physical memory attribute for a page is main memory, and the
-page has PBMT=2, then accesses to that page obey strong channel 0 I/O ordering
+page has PBMT=IO, then accesses to that page obey strong channel 0 I/O ordering
 rules with respect to other accesses to physical main memory and to other
-accesses to pages with PBMT=2.  Furthermore, accesses to such pages are
+accesses to pages with PBMT=IO.  Furthermore, accesses to such pages are
 considered I/O rather than main memory for the purposes of FENCE, {\em.aq}, and
 {\em.rl}.
 
@@ -2333,6 +2333,10 @@ be evicted from the cache by the latter.  If on the other hand the cacheable
 access appears after the non-cacheable access, then the former may remain
 cached as it normally would.
 
+The forthcoming Zicbom extension and the FENCE instruction will collectively
+form a standard mechanism for restoring coherence in scenarios with
+mismatched page attributes.
+
 Likewise, accesses performed under memory indicating the non-idempotent
 attribute must not be merged with idempotent accesses to the same region
 in flight at the same time, as the non-idempotency of the former must
@@ -2350,7 +2354,7 @@ A device driver written to rely on I/O strong ordering rules will not
 operate correctly if the address range is mapped as main memory by the
 page-based memory types.  As such, this configuration is discouraged.
 
-It will often still be useful to map physical I/O regions using PBMT=1 so that
+It will often still be useful to map physical I/O regions using PBMT=NC so that
 write combining and speculative accesses can be performed.  Such optimizations
 will likely improve performance when applied with adequate care.
 \end{commentary}