git: ac7f6d240079 - stable/13 - x86: add a comment providing source for numbers in legacy XSAVE area layout

The branch stable/13 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=ac7f6d24007949fb8ac951a7ff86d9da388004bb

commit ac7f6d24007949fb8ac951a7ff86d9da388004bb
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2021-12-13 23:25:36 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2021-12-15 01:41:29 +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 daf079b7d2cc..9b23cc5773a3 100644
--- a/sys/amd64/amd64/fpu.c
+++ b/sys/amd64/amd64/fpu.c
@@ -472,7 +472,8 @@ 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 4767d8896de9..dc04d84b0eb5 100644
--- a/sys/i386/i386/npx.c
+++ b/sys/i386/i386/npx.c
@@ -527,7 +527,10 @@ 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) +