linux-kernel - [RFC PATCH 5/7] crypto: x86/ghash - restructure FPU context saving

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Date:   Thu,  6 Oct 2022 17:31:49 -0500
From:   Robert Elliott <elliott@....com>
To:     herbert@...dor.apana.org.au, davem@...emloft.net,
        tim.c.chen@...ux.intel.com, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Robert Elliott <elliott@....com>
Subject: [RFC PATCH 5/7] crypto: x86/ghash - restructure FPU context saving

Wrap each of the calls to clmul_hash_update and clmul_ghash__mul
in its own set of kernel_fpu_begin and kernel_fpu_end calls, preparing
to limit the amount of data processed by each _update call to avoid
RCU stalls.

This is more like how polyval-clmulni_glue is structured.

Fixes: 0e1227d356e9 ("crypto: ghash - Add PCLMULQDQ accelerated implementation")
Suggested-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Robert Elliott <elliott@....com>
---
 arch/x86/crypto/ghash-clmulni-intel_glue.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/crypto/ghash-clmulni-intel_glue.c b/arch/x86/crypto/ghash-clmulni-intel_glue.c
index 3a96c167d78d..b25730c5b267 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
+++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
@@ -82,7 +82,6 @@ static int ghash_update(struct shash_desc *desc,
 	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
 	u8 *dst = dctx->buffer;
 
-	kernel_fpu_begin();
 	if (dctx->bytes) {
 		int n = min(srclen, dctx->bytes);
 		u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
@@ -93,10 +92,14 @@ static int ghash_update(struct shash_desc *desc,
 		while (n--)
 			*pos++ ^= *src++;
 
-		if (!dctx->bytes)
+		if (!dctx->bytes) {
+			kernel_fpu_begin();
 			clmul_ghash_mul(dst, &ctx->shash);
+			kernel_fpu_end();
+		}
 	}
 
+	kernel_fpu_begin();
 	clmul_ghash_update(dst, src, srclen, &ctx->shash);
 	kernel_fpu_end();
 
-- 
2.37.3