sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 264 insertions, 0 deletions

diff --git a/crypto/simd.c b/crypto/simd.c
new file mode 100644
index 000000000..4e29f7977
--- /dev/null
+++ b/crypto/simd.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Shared crypto simd helpers
+ *
+ * Copyright (c) 2012 Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
+ * Copyright (c) 2016 Herbert Xu <herbert@gondor.apana.org.au>
+ * Copyright (c) 2019 Google LLC
+ *
+ * Based on aesni-intel_glue.c by:
+ *  Copyright (C) 2008, Intel Corp.
+ *    Author: Huang Ying <ying.huang@intel.com>
+ */
+
+/*
+ * Shared crypto SIMD helpers.  These functions dynamically create and register
+ * an AEAD algorithm that wraps another, internal algorithm.  The wrapper
+ * ensures that the internal algorithm is only executed in a context where SIMD
+ * instructions are usable, i.e. where may_use_simd() returns true.  If SIMD is
+ * already usable, the wrapper directly calls the internal algorithm.  Otherwise
+ * it defers execution to a workqueue via cryptd.
+ *
+ * This is an alternative to the internal algorithm implementing a fallback for
+ * the !may_use_simd() case itself.
+ *
+ * Note that the wrapper algorithm is asynchronous, i.e. it has the
+ * CRYPTO_ALG_ASYNC flag set.  Therefore it won't be found by users who
+ * explicitly allocate a synchronous algorithm.
+ */
+
+#include <crypto/cryptd.h>
+#include <crypto/internal/aead.h>
+#include <crypto/internal/simd.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/preempt.h>
+#include <asm/simd.h>
+
+struct simd_aead_alg {
+	const char *ialg_name;
+	struct aead_alg alg;
+};
+
+struct simd_aead_ctx {
+	struct cryptd_aead *cryptd_tfm;
+};
+
+static int simd_aead_setkey(struct crypto_aead *tfm, const u8 *key,
+				unsigned int key_len)
+{
+	struct simd_aead_ctx *ctx = crypto_aead_ctx(tfm);
+	struct crypto_aead *child = &ctx->cryptd_tfm->base;
+
+	crypto_aead_clear_flags(child, CRYPTO_TFM_REQ_MASK);
+	crypto_aead_set_flags(child, crypto_aead_get_flags(tfm) &
+				     CRYPTO_TFM_REQ_MASK);
+	return crypto_aead_setkey(child, key, key_len);
+}
+
+static int simd_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
+{
+	struct simd_aead_ctx *ctx = crypto_aead_ctx(tfm);
+	struct crypto_aead *child = &ctx->cryptd_tfm->base;
+
+	return crypto_aead_setauthsize(child, authsize);
+}
+
+static int simd_aead_encrypt(struct aead_request *req)
+{
+	struct crypto_aead *tfm = crypto_aead_reqtfm(req);
+	struct simd_aead_ctx *ctx = crypto_aead_ctx(tfm);
+	struct aead_request *subreq;
+	struct crypto_aead *child;
+
+	subreq = aead_request_ctx(req);
+	*subreq = *req;
+
+	if (!crypto_simd_usable() ||
+	    (in_atomic() && cryptd_aead_queued(ctx->cryptd_tfm)))
+		child = &ctx->cryptd_tfm->base;
+	else
+		child = cryptd_aead_child(ctx->cryptd_tfm);
+
+	aead_request_set_tfm(subreq, child);
+
+	return crypto_aead_encrypt(subreq);
+}
+
+static int simd_aead_decrypt(struct aead_request *req)
+{
+	struct crypto_aead *tfm = crypto_aead_reqtfm(req);
+	struct simd_aead_ctx *ctx = crypto_aead_ctx(tfm);
+	struct aead_request *subreq;
+	struct crypto_aead *child;
+
+	subreq = aead_request_ctx(req);
+	*subreq = *req;
+
+	if (!crypto_simd_usable() ||
+	    (in_atomic() && cryptd_aead_queued(ctx->cryptd_tfm)))
+		child = &ctx->cryptd_tfm->base;
+	else
+		child = cryptd_aead_child(ctx->cryptd_tfm);
+
+	aead_request_set_tfm(subreq, child);
+
+	return crypto_aead_decrypt(subreq);
+}
+
+static void simd_aead_exit(struct crypto_aead *tfm)
+{
+	struct simd_aead_ctx *ctx = crypto_aead_ctx(tfm);
+
+	cryptd_free_aead(ctx->cryptd_tfm);
+}
+
+static int simd_aead_init(struct crypto_aead *tfm)
+{
+	struct simd_aead_ctx *ctx = crypto_aead_ctx(tfm);
+	struct cryptd_aead *cryptd_tfm;
+	struct simd_aead_alg *salg;
+	struct aead_alg *alg;
+	unsigned reqsize;
+
+	alg = crypto_aead_alg(tfm);
+	salg = container_of(alg, struct simd_aead_alg, alg);
+
+	cryptd_tfm = cryptd_alloc_aead(salg->ialg_name, CRYPTO_ALG_INTERNAL,
+				       CRYPTO_ALG_INTERNAL);
+	if (IS_ERR(cryptd_tfm))
+		return PTR_ERR(cryptd_tfm);
+
+	ctx->cryptd_tfm = cryptd_tfm;
+
+	reqsize = max(crypto_aead_reqsize(cryptd_aead_child(cryptd_tfm)),
+		      crypto_aead_reqsize(&cryptd_tfm->base));
+	reqsize += sizeof(struct aead_request);
+
+	crypto_aead_set_reqsize(tfm, reqsize);
+
+	return 0;
+}
+
+static struct simd_aead_alg *simd_aead_create_compat(struct aead_alg *ialg,
+						     const char *algname,
+						     const char *drvname,
+						     const char *basename)
+{
+	struct simd_aead_alg *salg;
+	struct aead_alg *alg;
+	int err;
+
+	salg = kzalloc_obj(*salg);
+	if (!salg) {
+		salg = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	salg->ialg_name = basename;
+	alg = &salg->alg;
+
+	err = -ENAMETOOLONG;
+	if (snprintf(alg->base.cra_name, CRYPTO_MAX_ALG_NAME, "%s", algname) >=
+	    CRYPTO_MAX_ALG_NAME)
+		goto out_free_salg;
+
+	if (snprintf(alg->base.cra_driver_name, CRYPTO_MAX_ALG_NAME, "%s",
+		     drvname) >= CRYPTO_MAX_ALG_NAME)
+		goto out_free_salg;
+
+	alg->base.cra_flags = CRYPTO_ALG_ASYNC |
+		(ialg->base.cra_flags & CRYPTO_ALG_INHERITED_FLAGS);
+	alg->base.cra_priority = ialg->base.cra_priority;
+	alg->base.cra_blocksize = ialg->base.cra_blocksize;
+	alg->base.cra_alignmask = ialg->base.cra_alignmask;
+	alg->base.cra_module = ialg->base.cra_module;
+	alg->base.cra_ctxsize = sizeof(struct simd_aead_ctx);
+
+	alg->ivsize = ialg->ivsize;
+	alg->maxauthsize = ialg->maxauthsize;
+	alg->chunksize = ialg->chunksize;
+
+	alg->init = simd_aead_init;
+	alg->exit = simd_aead_exit;
+
+	alg->setkey = simd_aead_setkey;
+	alg->setauthsize = simd_aead_setauthsize;
+	alg->encrypt = simd_aead_encrypt;
+	alg->decrypt = simd_aead_decrypt;
+
+	err = crypto_register_aead(alg);
+	if (err)
+		goto out_free_salg;
+
+out:
+	return salg;
+
+out_free_salg:
+	kfree(salg);
+	salg = ERR_PTR(err);
+	goto out;
+}
+
+static void simd_aead_free(struct simd_aead_alg *salg)
+{
+	crypto_unregister_aead(&salg->alg);
+	kfree(salg);
+}
+
+int simd_register_aeads_compat(struct aead_alg *algs, int count,
+			       struct simd_aead_alg **simd_algs)
+{
+	int err;
+	int i;
+	const char *algname;
+	const char *drvname;
+	const char *basename;
+	struct simd_aead_alg *simd;
+
+	for (i = 0; i < count; i++) {
+		if (WARN_ON(strncmp(algs[i].base.cra_name, "__", 2) ||
+			    strncmp(algs[i].base.cra_driver_name, "__", 2)))
+			return -EINVAL;
+	}
+
+	err = crypto_register_aeads(algs, count);
+	if (err)
+		return err;
+
+	for (i = 0; i < count; i++) {
+		algname = algs[i].base.cra_name + 2;
+		drvname = algs[i].base.cra_driver_name + 2;
+		basename = algs[i].base.cra_driver_name;
+		simd = simd_aead_create_compat(algs + i, algname, drvname, basename);
+		err = PTR_ERR(simd);
+		if (IS_ERR(simd))
+			goto err_unregister;
+		simd_algs[i] = simd;
+	}
+	return 0;
+
+err_unregister:
+	simd_unregister_aeads(algs, count, simd_algs);
+	return err;
+}
+EXPORT_SYMBOL_GPL(simd_register_aeads_compat);
+
+void simd_unregister_aeads(struct aead_alg *algs, int count,
+			   struct simd_aead_alg **simd_algs)
+{
+	int i;
+
+	crypto_unregister_aeads(algs, count);
+
+	for (i = 0; i < count; i++) {
+		if (simd_algs[i]) {
+			simd_aead_free(simd_algs[i]);
+			simd_algs[i] = NULL;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(simd_unregister_aeads);
+
+MODULE_DESCRIPTION("Shared crypto SIMD helpers");
+MODULE_LICENSE("GPL");