git: 9d18bf1daff5 - stable/12 - x86: add a comment providing source for numbers in legacy XSAVE area layout

The branch stable/12 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=9d18bf1daff5b0feb64411494ce5ceadf3d70b1b

commit 9d18bf1daff5b0feb64411494ce5ceadf3d70b1b
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-12-13 23:25:36 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2021-12-15 01:56:32 +0000

    x86: add a comment providing source for numbers in legacy XSAVE area layout
    
    (cherry picked from commit 0e6b06d5c8719597b2ec59e6856b5decbd9e65f6)
---
 sys/amd64/amd64/fpu.c | 3 ++-
 sys/i386/i386/npx.c   | 5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/sys/amd64/amd64/fpu.c b/sys/amd64/amd64/fpu.c
index d17241bf2523..91df1259be46 100644
--- a/sys/amd64/amd64/fpu.c
+++ b/sys/amd64/amd64/fpu.c
@@ -465,7 +465,8 @@ fpuinitstate(void *arg __unused)
 
 	/*
 	 * Create a table describing the layout of the CPU Extended
-	 * Save Area.
+	 * Save Area.  See Intel SDM rev. 075 Vol. 1 13.4.1 "Legacy
+	 * Region of an XSAVE Area" for the source of offsets/sizes.
 	 */
 	if (use_xsave) {
 		xstate_bv = (uint64_t *)((char *)(fpu_initialstate + 1) +
diff --git a/sys/i386/i386/npx.c b/sys/i386/i386/npx.c
index c64ef4ca895f..abf3ab5bd6df 100644
--- a/sys/i386/i386/npx.c
+++ b/sys/i386/i386/npx.c
@@ -515,7 +515,10 @@ npxinitstate(void *arg __unused)
 
 	/*
 	 * Create a table describing the layout of the CPU Extended
-	 * Save Area.
+	 * Save Area.  See Intel SDM rev. 075 Vol. 1 13.4.1 "Legacy
+	 * Region of an XSAVE Area" for the source of offsets/sizes.
+	 * Note that 32bit XSAVE does not use %xmm8-%xmm15, see
+	 * 10.5.1.2 and 13.5.2 "SSE State".
 	 */
 	if (use_xsave) {
 		xstate_bv = (uint64_t *)((char *)(npx_initialstate + 1) +