[PATCH v3 05/17] crypto: x86/crc - limit FPU preemption

[Robert Elliott <elliott@hpe.com>]

Limit the number of bytes processed between kernel_fpu_begin() and
kernel_fpu_end() calls.

Those functions call preempt_disable() and preempt_enable(), so
the CPU core is unavailable for scheduling while running, leading to:
    rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: ...

Fixes: 78c37d191dd6 ("crypto: crc32 - add crc32 pclmulqdq implementation and wrappers for table implementation")
Fixes: 6a8ce1ef3940 ("crypto: crc32c - Optimize CRC32C calculation with PCLMULQDQ instruction")
Fixes: 0b95a7f85718 ("crypto: crct10dif - Glue code to cast accelerated CRCT10DIF assembly as a crypto transform")
Suggested-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Robert Elliott <elliott@hpe.com>

---
v3 use while loops and static int, simplify one of the loop structures,
add algorithm-specific limits, use local stack variable in crc32 finup
rather than the context pointer like update uses
---
 arch/x86/crypto/crc32-pclmul_asm.S      |  6 +--
 arch/x86/crypto/crc32-pclmul_glue.c     | 27 +++++++++----
 arch/x86/crypto/crc32c-intel_glue.c     | 52 ++++++++++++++++++-------
 arch/x86/crypto/crct10dif-pclmul_glue.c | 48 +++++++++++++++++------
 4 files changed, 99 insertions(+), 34 deletions(-)

diff --git a/arch/x86/crypto/crc32-pclmul_asm.S b/arch/x86/crypto/crc32-pclmul_asm.S
index ca53e96996ac..9abd861636c3 100644
--- a/arch/x86/crypto/crc32-pclmul_asm.S
+++ b/arch/x86/crypto/crc32-pclmul_asm.S
@@ -72,15 +72,15 @@
 .text
 /**
  *      Calculate crc32
- *      BUF - buffer (16 bytes aligned)
- *      LEN - sizeof buffer (16 bytes aligned), LEN should be grater than 63
+ *      BUF - buffer - must be 16 bytes aligned
+ *      LEN - sizeof buffer - must be multiple of 16 bytes and greater than 63
  *      CRC - initial crc32
  *      return %eax crc32
  *      uint crc32_pclmul_le_16(unsigned char const *buffer,
  *	                     size_t len, uint crc32)
  */
 
-SYM_FUNC_START(crc32_pclmul_le_16) /* buffer and buffer size are 16 bytes aligned */
+SYM_FUNC_START(crc32_pclmul_le_16)
 	movdqa  (BUF), %xmm1
 	movdqa  0x10(BUF), %xmm2
 	movdqa  0x20(BUF), %xmm3
diff --git a/arch/x86/crypto/crc32-pclmul_glue.c b/arch/x86/crypto/crc32-pclmul_glue.c
index 98cf3b4e4c9f..df3dbc754818 100644
--- a/arch/x86/crypto/crc32-pclmul_glue.c
+++ b/arch/x86/crypto/crc32-pclmul_glue.c
@@ -46,6 +46,9 @@
 #define SCALE_F			16L	/* size of xmm register */
 #define SCALE_F_MASK		(SCALE_F - 1)
 
+/* avoid kernel_fpu_begin/end scheduler/rcu stalls */
+static const unsigned int bytes_per_fpu = 655 * 1024;
+
 u32 crc32_pclmul_le_16(unsigned char const *buffer, size_t len, u32 crc32);
 
 static u32 __attribute__((pure))
@@ -55,6 +58,9 @@ static u32 __attribute__((pure))
 	unsigned int iremainder;
 	unsigned int prealign;
 
+	BUILD_BUG_ON(bytes_per_fpu < PCLMUL_MIN_LEN);
+	BUILD_BUG_ON(bytes_per_fpu & SCALE_F_MASK);
+
 	if (len < PCLMUL_MIN_LEN + SCALE_F_MASK || !crypto_simd_usable())
 		return crc32_le(crc, p, len);
 
@@ -70,12 +76,19 @@ static u32 __attribute__((pure))
 	iquotient = len & (~SCALE_F_MASK);
 	iremainder = len & SCALE_F_MASK;
 
-	kernel_fpu_begin();
-	crc = crc32_pclmul_le_16(p, iquotient, crc);
-	kernel_fpu_end();
+	while (iquotient >= PCLMUL_MIN_LEN) {
+		unsigned int chunk = min(iquotient, bytes_per_fpu);
+
+		kernel_fpu_begin();
+		crc = crc32_pclmul_le_16(p, chunk, crc);
+		kernel_fpu_end();
+
+		iquotient -= chunk;
+		p += chunk;
+	}
 
-	if (iremainder)
-		crc = crc32_le(crc, p + iquotient, iremainder);
+	if (iquotient || iremainder)
+		crc = crc32_le(crc, p, iquotient + iremainder);
 
 	return crc;
 }
@@ -120,8 +133,8 @@ static int crc32_pclmul_update(struct shash_desc *desc, const u8 *data,
 }
 
 /* No final XOR 0xFFFFFFFF, like crc32_le */
-static int __crc32_pclmul_finup(u32 *crcp, const u8 *data, unsigned int len,
-				u8 *out)
+static int __crc32_pclmul_finup(const u32 *crcp, const u8 *data,
+				unsigned int len, u8 *out)
 {
 	*(__le32 *)out = cpu_to_le32(crc32_pclmul_le(*crcp, data, len));
 	return 0;
diff --git a/arch/x86/crypto/crc32c-intel_glue.c b/arch/x86/crypto/crc32c-intel_glue.c
index feccb5254c7e..f08ed68ec93d 100644
--- a/arch/x86/crypto/crc32c-intel_glue.c
+++ b/arch/x86/crypto/crc32c-intel_glue.c
@@ -45,7 +45,10 @@ asmlinkage unsigned int crc_pcl(const u8 *buffer, int len,
 				unsigned int crc_init);
 #endif /* CONFIG_X86_64 */
 
-static u32 crc32c_intel_le_hw_byte(u32 crc, unsigned char const *data, size_t length)
+/* avoid kernel_fpu_begin/end scheduler/rcu stalls */
+static const unsigned int bytes_per_fpu = 868 * 1024;
+
+static u32 crc32c_intel_le_hw_byte(u32 crc, const unsigned char *data, size_t length)
 {
 	while (length--) {
 		asm("crc32b %1, %0"
@@ -56,7 +59,7 @@ static u32 crc32c_intel_le_hw_byte(u32 crc, unsigned char const *data, size_t le
 	return crc;
 }
 
-static u32 __pure crc32c_intel_le_hw(u32 crc, unsigned char const *p, size_t len)
+static u32 __pure crc32c_intel_le_hw(u32 crc, const unsigned char *p, size_t len)
 {
 	unsigned int iquotient = len / SCALE_F;
 	unsigned int iremainder = len % SCALE_F;
@@ -110,8 +113,8 @@ static int crc32c_intel_update(struct shash_desc *desc, const u8 *data,
 	return 0;
 }
 
-static int __crc32c_intel_finup(u32 *crcp, const u8 *data, unsigned int len,
-				u8 *out)
+static int __crc32c_intel_finup(const u32 *crcp, const u8 *data,
+				unsigned int len, u8 *out)
 {
 	*(__le32 *)out = ~cpu_to_le32(crc32c_intel_le_hw(*crcp, data, len));
 	return 0;
@@ -153,29 +156,52 @@ static int crc32c_pcl_intel_update(struct shash_desc *desc, const u8 *data,
 {
 	u32 *crcp = shash_desc_ctx(desc);
 
+	BUILD_BUG_ON(bytes_per_fpu < CRC32C_PCL_BREAKEVEN);
+	BUILD_BUG_ON(bytes_per_fpu % SCALE_F);
+
 	/*
 	 * use faster PCL version if datasize is large enough to
 	 * overcome kernel fpu state save/restore overhead
 	 */
 	if (len >= CRC32C_PCL_BREAKEVEN && crypto_simd_usable()) {
-		kernel_fpu_begin();
-		*crcp = crc_pcl(data, len, *crcp);
-		kernel_fpu_end();
+		while (len) {
+			unsigned int chunk = min(len, bytes_per_fpu);
+
+			kernel_fpu_begin();
+			*crcp = crc_pcl(data, chunk, *crcp);
+			kernel_fpu_end();
+
+			len -= chunk;
+			data += chunk;
+		}
 	} else
 		*crcp = crc32c_intel_le_hw(*crcp, data, len);
 	return 0;
 }
 
-static int __crc32c_pcl_intel_finup(u32 *crcp, const u8 *data, unsigned int len,
-				u8 *out)
+static int __crc32c_pcl_intel_finup(const u32 *crcp, const u8 *data,
+				    unsigned int len, u8 *out)
 {
+	u32 crc = *crcp;
+
+	BUILD_BUG_ON(bytes_per_fpu < CRC32C_PCL_BREAKEVEN);
+	BUILD_BUG_ON(bytes_per_fpu % SCALE_F);
+
 	if (len >= CRC32C_PCL_BREAKEVEN && crypto_simd_usable()) {
-		kernel_fpu_begin();
-		*(__le32 *)out = ~cpu_to_le32(crc_pcl(data, len, *crcp));
-		kernel_fpu_end();
+		while (len) {
+			unsigned int chunk = min(len, bytes_per_fpu);
+
+			kernel_fpu_begin();
+			crc = crc_pcl(data, chunk, crc);
+			kernel_fpu_end();
+
+			len -= chunk;
+			data += chunk;
+		}
+		*(__le32 *)out = ~cpu_to_le32(crc);
 	} else
 		*(__le32 *)out =
-			~cpu_to_le32(crc32c_intel_le_hw(*crcp, data, len));
+			~cpu_to_le32(crc32c_intel_le_hw(crc, data, len));
 	return 0;
 }
 
diff --git a/arch/x86/crypto/crct10dif-pclmul_glue.c b/arch/x86/crypto/crct10dif-pclmul_glue.c
index 71291d5af9f4..4f6b8c727d88 100644
--- a/arch/x86/crypto/crct10dif-pclmul_glue.c
+++ b/arch/x86/crypto/crct10dif-pclmul_glue.c
@@ -34,6 +34,11 @@
 #include <asm/cpu_device_id.h>
 #include <asm/simd.h>
 
+#define PCLMUL_MIN_LEN 16U /* minimum size of buffer for crc_t10dif_pcl */
+
+/* avoid kernel_fpu_begin/end scheduler/rcu stalls */
+static const unsigned int bytes_per_fpu = 614 * 1024;
+
 asmlinkage u16 crc_t10dif_pcl(u16 init_crc, const u8 *buf, size_t len);
 
 struct chksum_desc_ctx {
@@ -54,11 +59,21 @@ static int chksum_update(struct shash_desc *desc, const u8 *data,
 {
 	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 
-	if (length >= 16 && crypto_simd_usable()) {
-		kernel_fpu_begin();
-		ctx->crc = crc_t10dif_pcl(ctx->crc, data, length);
-		kernel_fpu_end();
-	} else
+	BUILD_BUG_ON(bytes_per_fpu < PCLMUL_MIN_LEN);
+
+	if (length >= PCLMUL_MIN_LEN && crypto_simd_usable()) {
+		while (length >= PCLMUL_MIN_LEN) {
+			unsigned int chunk = min(length, bytes_per_fpu);
+
+			kernel_fpu_begin();
+			ctx->crc = crc_t10dif_pcl(ctx->crc, data, chunk);
+			kernel_fpu_end();
+
+			length -= chunk;
+			data += chunk;
+		}
+	}
+	if (length)
 		ctx->crc = crc_t10dif_generic(ctx->crc, data, length);
 	return 0;
 }
@@ -73,12 +88,23 @@ static int chksum_final(struct shash_desc *desc, u8 *out)
 
 static int __chksum_finup(__u16 crc, const u8 *data, unsigned int len, u8 *out)
 {
-	if (len >= 16 && crypto_simd_usable()) {
-		kernel_fpu_begin();
-		*(__u16 *)out = crc_t10dif_pcl(crc, data, len);
-		kernel_fpu_end();
-	} else
-		*(__u16 *)out = crc_t10dif_generic(crc, data, len);
+	BUILD_BUG_ON(bytes_per_fpu < PCLMUL_MIN_LEN);
+
+	if (len >= PCLMUL_MIN_LEN && crypto_simd_usable()) {
+		while (len >= PCLMUL_MIN_LEN) {
+			unsigned int chunk = min(len, bytes_per_fpu);
+
+			kernel_fpu_begin();
+			crc = crc_t10dif_pcl(crc, data, chunk);
+			kernel_fpu_end();
+
+			len -= chunk;
+			data += chunk;
+		}
+	}
+	if (len)
+		crc = crc_t10dif_generic(crc, data, len);
+	*(__u16 *)out = crc;
 	return 0;
 }
 
-- 
2.37.3