linux-kernel - [PATCH] x86/csum: fix compilation error for UM

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Date:   Thu, 18 Nov 2021 09:52:39 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Johannes Berg <johannes.berg@...el.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] x86/csum: fix compilation error for UM

From: Eric Dumazet <edumazet@...gle.com>

load_unaligned_zeropad() is not yet universal.

ARCH=um SUBARCH=x86_64 builds do not have it.

When CONFIG_DCACHE_WORD_ACCESS is not set, simply continue
the bisection with 4, 2 and 1 byte steps.

Fixes: df4554cebdaa ("x86/csum: Rewrite/optimize csum_partial()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Duyck <alexanderduyck@...com>
Cc: Johannes Berg <johannes.berg@...el.com>
Reported-by: kernel test robot <lkp@...el.com>
---
 arch/x86/lib/csum-partial_64.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index 5ec35626945b6db2f7f41c6d46d5e422810eac46..1eb8f2d11f7c785be624eba315fe9ca7989fd56d 100644
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -92,6 +92,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
 		buff += 8;
 	}
 	if (len & 7) {
+#ifdef CONFIG_DCACHE_WORD_ACCESS
 		unsigned int shift = (8 - (len & 7)) * 8;
 		unsigned long trail;
 
@@ -101,6 +102,31 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
 		    "adcq $0,%[res]"
 			: [res] "+r" (temp64)
 			: [trail] "r" (trail));
+#else
+		if (len & 4) {
+			asm("addq %[val],%[res]\n\t"
+			    "adcq $0,%[res]"
+				: [res] "+r" (temp64)
+				: [val] "r" ((u64)*(u32 *)buff)
+				: "memory");
+			buff += 4;
+		}
+		if (len & 2) {
+			asm("addq %[val],%[res]\n\t"
+			    "adcq $0,%[res]"
+				: [res] "+r" (temp64)
+				: [val] "r" ((u64)*(u16 *)buff)
+				: "memory");
+			buff += 2;
+		}
+		if (len & 1) {
+			asm("addq %[val],%[res]\n\t"
+			    "adcq $0,%[res]"
+				: [res] "+r" (temp64)
+				: [val] "r" ((u64)*(u8 *)buff)
+				: "memory");
+		}
+#endif
 	}
 	result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff);
 	if (unlikely(odd)) { 
-- 
2.34.0.rc1.387.gb447b232ab-goog