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crypto: riscv - parallelize AES-CBC decryption

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Since CBC decryption is parallelizable, make the RISC-V implementation
of AES-CBC decryption process multiple blocks at a time, instead of
processing the blocks one by one.  This should improve performance.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240208060851.154129-1-ebiggers@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Eric Biggers 2024-02-07 22:08:51 -08:00 committed by Palmer Dabbelt
parent 028d1aee1f
commit da215b089b
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GPG Key ID: 2E1319F35FBB1889
1 changed files with 15 additions and 9 deletions
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24
arch/riscv/crypto/aes-riscv64-zvkned.S
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@ -139,19 +139,25 @@ SYM_FUNC_END(aes_ecb_decrypt_zvkned)
.endm
.macro aes_cbc_decrypt keylen
srli LEN, LEN, 2 // Convert LEN from bytes to words
vle32.v v16, (IVP) // Load IV
1:
vle32.v v17, (INP) // Load ciphertext block
vmv.v.v v18, v17 // Save ciphertext block
aes_decrypt v17, \keylen // Decrypt
vxor.vv v17, v17, v16 // XOR with IV or prev ciphertext block
vse32.v v17, (OUTP) // Store plaintext block
vmv.v.v v16, v18 // Next "IV" is prev ciphertext block
addi INP, INP, 16
addi OUTP, OUTP, 16
addi LEN, LEN, -16
vsetvli t0, LEN, e32, m4, ta, ma
vle32.v v20, (INP) // Load ciphertext blocks
vslideup.vi v16, v20, 4 // Setup prev ciphertext blocks
addi t1, t0, -4
vslidedown.vx v24, v20, t1 // Save last ciphertext block
aes_decrypt v20, \keylen // Decrypt the blocks
vxor.vv v20, v20, v16 // XOR with prev ciphertext blocks
vse32.v v20, (OUTP) // Store plaintext blocks
vmv.v.v v16, v24 // Next "IV" is last ciphertext block
slli t1, t0, 2 // Words to bytes
add INP, INP, t1
add OUTP, OUTP, t1
sub LEN, LEN, t0
bnez LEN, 1b
vsetivli zero, 4, e32, m1, ta, ma
vse32.v v16, (IVP) // Store next IV
ret
.endm