[PATCH v2 1/6] riscv: hwprobe: Report FP extensions only when available

[Radim Krčmář]

User-mode use of floating-point extensions requires non-Off sstatus.FS,
which we set only when has_fpu() (CONFIG_FPU and D on all harts).
The vector floating-point extensions require non-Off sstatus.FS too, but
hwprobe gates them only on has_vector() (CONFIG_ISA_V and Zve32x on all
harts).

CONFIG_ISA_V depends on CONFIG_FPU, because V extension implies Zve64d,
but has_vector() only requires Zve32x, so has_vector() doesn't imply
has_fpu(), hence we can boot on a machine where all harts have Zve32x,
but not all harts have D.

hwprobe currently reports the extensions from the per-hart ISA bitmaps
alone, so it can advertise extensions that are always disabled in
user-mode.  Report correct environment to user-mode.

Fixes: 2e2cf5581fcc ("riscv: cpufeature: add validation for zfa, zfh and zfhmin")
Fixes: de8f8282a969 ("riscv: hwprobe: add zve Vector subextensions into hwprobe interface")
Fixes: 5dadda5e6a59 ("riscv: hwprobe: export Zvfh[min] ISA extensions")
Fixes: a4863e002cf0 ("riscv: hwprobe: export bfloat16 ISA extension")
Reviewed-by: Andy Chiu <tchiu at tenstorrent.com>
Signed-off-by: Radim Krčmář <radim.krcmar at oss.qualcomm.com>
---
v2:
* added one more "Fixes:" for bfloat
* hopefully clarified the commit message around CONFIGs
* added r-b
---
 arch/riscv/kernel/sys_hwprobe.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index cd7cf272e6e1..feae40466e2b 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -146,15 +146,8 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 		if (has_vector()) {
 			EXT_KEY(isainfo->isa, ZVBB, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVBC, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVE32F, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVE32X, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVE64D, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVE64F, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVE64X, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVFBFMIN, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVFBFWMA, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVFH, pair->value, missing);
-			EXT_KEY(isainfo->isa, ZVFHMIN, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVKB, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVKG, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVKNED, pair->value, missing);
@@ -163,14 +156,26 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 			EXT_KEY(isainfo->isa, ZVKSED, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVKSH, pair->value, missing);
 			EXT_KEY(isainfo->isa, ZVKT, pair->value, missing);
+
+			if (has_fpu()) {
+				EXT_KEY(isainfo->isa, ZVE32F, pair->value, missing);
+				EXT_KEY(isainfo->isa, ZVE64D, pair->value, missing);
+				EXT_KEY(isainfo->isa, ZVE64F, pair->value, missing);
+				EXT_KEY(isainfo->isa, ZVFBFMIN, pair->value, missing);
+				EXT_KEY(isainfo->isa, ZVFBFWMA, pair->value, missing);
+				EXT_KEY(isainfo->isa, ZVFH, pair->value, missing);
+				EXT_KEY(isainfo->isa, ZVFHMIN, pair->value, missing);
+			}
 		}
 
-		EXT_KEY(isainfo->isa, ZCD, pair->value, missing);
-		EXT_KEY(isainfo->isa, ZCF, pair->value, missing);
-		EXT_KEY(isainfo->isa, ZFA, pair->value, missing);
-		EXT_KEY(isainfo->isa, ZFBFMIN, pair->value, missing);
-		EXT_KEY(isainfo->isa, ZFH, pair->value, missing);
-		EXT_KEY(isainfo->isa, ZFHMIN, pair->value, missing);
+		if (has_fpu()) {
+			EXT_KEY(isainfo->isa, ZCD, pair->value, missing);
+			EXT_KEY(isainfo->isa, ZCF, pair->value, missing);
+			EXT_KEY(isainfo->isa, ZFA, pair->value, missing);
+			EXT_KEY(isainfo->isa, ZFBFMIN, pair->value, missing);
+			EXT_KEY(isainfo->isa, ZFH, pair->value, missing);
+			EXT_KEY(isainfo->isa, ZFHMIN, pair->value, missing);
+		}
 
 		if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM))
 			EXT_KEY(isainfo->isa, SUPM, pair->value, missing);
-- 
2.55.0