2022-12-19 22:05:24

by Elliott, Robert (Servers)

Subject: [PATCH 07/13] 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 <[email protected]>
Signed-off-by: Robert Elliott <[email protected]>
---
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 beac4b2eddf6..1bfde099de0f 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
+++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
@@ -80,7 +80,6 @@ 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);
@@ -91,10 +90,14 @@ 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();

--
2.38.1

2022-12-30 09:06:40

by Herbert Xu

Subject: Re: [PATCH 07/13] crypto: x86/ghash - restructure FPU context saving

On Mon, Dec 19, 2022 at 04:02:17PM -0600, Robert Elliott wrote:
> 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 <[email protected]>
> Signed-off-by: Robert Elliott <[email protected]>
> ---
> 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 beac4b2eddf6..1bfde099de0f 100644
> --- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
> +++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
> @@ -80,7 +80,6 @@ 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);
> @@ -91,10 +90,14 @@ 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();

Why is this necessary? Couldn't you just add the kernel_fpu_yield
calls even without this patch?

This just seems to be adding some unnecessary begin/end calls.

Cheers,
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt