KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 434 insertions, 0 deletions

diff --git a/drivers/crypto/qce/skcipher.c b/drivers/crypto/qce/skcipher.c
new file mode 100644
index 000000000..4931b064f
--- /dev/null
+++ b/drivers/crypto/qce/skcipher.c
@@ -0,0 +1,434 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2010-2014, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
+#include <linux/moduleparam.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <crypto/aes.h>
+#include <crypto/internal/skcipher.h>
+
+#include "cipher.h"
+
+static unsigned int aes_sw_max_len = CONFIG_CRYPTO_DEV_QCE_SW_MAX_LEN;
+module_param(aes_sw_max_len, uint, 0644);
+MODULE_PARM_DESC(aes_sw_max_len,
+		 "Only use hardware for AES requests larger than this "
+		 "[0=always use hardware; anything <16 breaks AES-GCM; default="
+		 __stringify(CONFIG_CRYPTO_DEV_QCE_SW_MAX_LEN)"]");
+
+static LIST_HEAD(skcipher_algs);
+
+static void qce_skcipher_done(void *data)
+{
+	struct crypto_async_request *async_req = data;
+	struct skcipher_request *req = skcipher_request_cast(async_req);
+	struct qce_cipher_reqctx *rctx = skcipher_request_ctx(req);
+	struct qce_alg_template *tmpl = to_cipher_tmpl(crypto_skcipher_reqtfm(req));
+	struct qce_device *qce = tmpl->qce;
+	struct qce_result_dump *result_buf = qce->dma.result_buf;
+	enum dma_data_direction dir_src, dir_dst;
+	u32 status;
+	int error;
+	bool diff_dst;
+
+	diff_dst = (req->src != req->dst) ? true : false;
+	dir_src = diff_dst ? DMA_TO_DEVICE : DMA_BIDIRECTIONAL;
+	dir_dst = diff_dst ? DMA_FROM_DEVICE : DMA_BIDIRECTIONAL;
+
+	error = qce_dma_terminate_all(&qce->dma);
+	if (error)
+		dev_dbg(qce->dev, "skcipher dma termination error (%d)\n",
+			error);
+
+	if (diff_dst)
+		dma_unmap_sg(qce->dev, rctx->src_sg, rctx->src_nents, dir_src);
+	dma_unmap_sg(qce->dev, rctx->dst_sg, rctx->dst_nents, dir_dst);
+
+	sg_free_table(&rctx->dst_tbl);
+
+	error = qce_check_status(qce, &status);
+	if (error < 0)
+		dev_dbg(qce->dev, "skcipher operation error (%x)\n", status);
+
+	memcpy(rctx->iv, result_buf->encr_cntr_iv, rctx->ivsize);
+	qce->async_req_done(tmpl->qce, error);
+}
+
+static int
+qce_skcipher_async_req_handle(struct crypto_async_request *async_req)
+{
+	struct skcipher_request *req = skcipher_request_cast(async_req);
+	struct qce_cipher_reqctx *rctx = skcipher_request_ctx(req);
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct qce_alg_template *tmpl = to_cipher_tmpl(crypto_skcipher_reqtfm(req));
+	struct qce_device *qce = tmpl->qce;
+	enum dma_data_direction dir_src, dir_dst;
+	struct scatterlist *sg;
+	bool diff_dst;
+	gfp_t gfp;
+	int dst_nents, src_nents, ret;
+
+	rctx->iv = req->iv;
+	rctx->ivsize = crypto_skcipher_ivsize(skcipher);
+	rctx->cryptlen = req->cryptlen;
+
+	diff_dst = (req->src != req->dst) ? true : false;
+	dir_src = diff_dst ? DMA_TO_DEVICE : DMA_BIDIRECTIONAL;
+	dir_dst = diff_dst ? DMA_FROM_DEVICE : DMA_BIDIRECTIONAL;
+
+	rctx->src_nents = sg_nents_for_len(req->src, req->cryptlen);
+	if (diff_dst)
+		rctx->dst_nents = sg_nents_for_len(req->dst, req->cryptlen);
+	else
+		rctx->dst_nents = rctx->src_nents;
+	if (rctx->src_nents < 0) {
+		dev_err(qce->dev, "Invalid numbers of src SG.\n");
+		return rctx->src_nents;
+	}
+	if (rctx->dst_nents < 0) {
+		dev_err(qce->dev, "Invalid numbers of dst SG.\n");
+		return -rctx->dst_nents;
+	}
+
+	rctx->dst_nents += 1;
+
+	gfp = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ?
+						GFP_KERNEL : GFP_ATOMIC;
+
+	ret = sg_alloc_table(&rctx->dst_tbl, rctx->dst_nents, gfp);
+	if (ret)
+		return ret;
+
+	sg_init_one(&rctx->result_sg, qce->dma.result_buf, QCE_RESULT_BUF_SZ);
+
+	sg = qce_sgtable_add(&rctx->dst_tbl, req->dst, req->cryptlen);
+	if (IS_ERR(sg)) {
+		ret = PTR_ERR(sg);
+		goto error_free;
+	}
+
+	sg = qce_sgtable_add(&rctx->dst_tbl, &rctx->result_sg,
+			     QCE_RESULT_BUF_SZ);
+	if (IS_ERR(sg)) {
+		ret = PTR_ERR(sg);
+		goto error_free;
+	}
+
+	sg_mark_end(sg);
+	rctx->dst_sg = rctx->dst_tbl.sgl;
+
+	dst_nents = dma_map_sg(qce->dev, rctx->dst_sg, rctx->dst_nents, dir_dst);
+	if (!dst_nents) {
+		ret = -EIO;
+		goto error_free;
+	}
+
+	if (diff_dst) {
+		src_nents = dma_map_sg(qce->dev, req->src, rctx->src_nents, dir_src);
+		if (!src_nents) {
+			ret = -EIO;
+			goto error_unmap_dst;
+		}
+		rctx->src_sg = req->src;
+	} else {
+		rctx->src_sg = rctx->dst_sg;
+		src_nents = dst_nents - 1;
+	}
+
+	ret = qce_dma_prep_sgs(&qce->dma, rctx->src_sg, src_nents,
+			       rctx->dst_sg, dst_nents,
+			       qce_skcipher_done, async_req);
+	if (ret)
+		goto error_unmap_src;
+
+	qce_dma_issue_pending(&qce->dma);
+
+	ret = qce_start(async_req, tmpl->crypto_alg_type);
+	if (ret)
+		goto error_terminate;
+
+	return 0;
+
+error_terminate:
+	qce_dma_terminate_all(&qce->dma);
+error_unmap_src:
+	if (diff_dst)
+		dma_unmap_sg(qce->dev, req->src, rctx->src_nents, dir_src);
+error_unmap_dst:
+	dma_unmap_sg(qce->dev, rctx->dst_sg, rctx->dst_nents, dir_dst);
+error_free:
+	sg_free_table(&rctx->dst_tbl);
+	return ret;
+}
+
+static int qce_skcipher_setkey(struct crypto_skcipher *ablk, const u8 *key,
+				 unsigned int keylen)
+{
+	struct crypto_tfm *tfm = crypto_skcipher_tfm(ablk);
+	struct qce_cipher_ctx *ctx = crypto_tfm_ctx(tfm);
+	unsigned long flags = to_cipher_tmpl(ablk)->alg_flags;
+	unsigned int __keylen;
+	int ret;
+
+	if (!key || !keylen)
+		return -EINVAL;
+
+	/*
+	 * AES XTS key1 = key2 not supported by crypto engine.
+	 * Revisit to request a fallback cipher in this case.
+	 */
+	if (IS_XTS(flags)) {
+		__keylen = keylen >> 1;
+		if (!memcmp(key, key + __keylen, __keylen))
+			return -ENOKEY;
+	} else {
+		__keylen = keylen;
+	}
+
+	switch (__keylen) {
+	case AES_KEYSIZE_128:
+	case AES_KEYSIZE_256:
+		memcpy(ctx->enc_key, key, keylen);
+		break;
+	case AES_KEYSIZE_192:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	ret = crypto_skcipher_setkey(ctx->fallback, key, keylen);
+	if (!ret)
+		ctx->enc_keylen = keylen;
+	return ret;
+}
+
+static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct qce_cipher_ctx *ctx = crypto_skcipher_ctx(tfm);
+	struct qce_cipher_reqctx *rctx = skcipher_request_ctx(req);
+	struct qce_alg_template *tmpl = to_cipher_tmpl(tfm);
+	unsigned int blocksize = crypto_skcipher_blocksize(tfm);
+	int keylen;
+
+	rctx->flags = tmpl->alg_flags;
+	rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
+	keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
+
+	/* CE does not handle 0 length messages */
+	if (!req->cryptlen)
+		return 0;
+
+	/*
+	 * ECB and CBC algorithms require message lengths to be
+	 * multiples of block size.
+	 */
+	if (IS_CBC(rctx->flags))
+		if (!IS_ALIGNED(req->cryptlen, blocksize))
+			return -EINVAL;
+
+	/*
+	 * Conditions for requesting a fallback cipher
+	 * AES-192 (not supported by crypto engine (CE))
+	 * AES-XTS request with len <= 512 byte (not recommended to use CE)
+	 * AES-XTS request with len > QCE_SECTOR_SIZE and
+	 * is not a multiple of it.(Revisit this condition to check if it is
+	 * needed in all versions of CE)
+	 */
+	if (IS_AES(rctx->flags) &&
+	    ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
+	    (IS_XTS(rctx->flags) && ((req->cryptlen <= aes_sw_max_len) ||
+	    (req->cryptlen > QCE_SECTOR_SIZE &&
+	    req->cryptlen % QCE_SECTOR_SIZE))))) {
+		skcipher_request_set_tfm(&rctx->fallback_req, ctx->fallback);
+		skcipher_request_set_callback(&rctx->fallback_req,
+					      req->base.flags,
+					      req->base.complete,
+					      req->base.data);
+		skcipher_request_set_crypt(&rctx->fallback_req, req->src,
+					   req->dst, req->cryptlen, req->iv);
+		return encrypt ? crypto_skcipher_encrypt(&rctx->fallback_req) :
+				 crypto_skcipher_decrypt(&rctx->fallback_req);
+	}
+
+	return tmpl->qce->async_req_enqueue(tmpl->qce, &req->base);
+}
+
+static int qce_skcipher_encrypt(struct skcipher_request *req)
+{
+	return qce_skcipher_crypt(req, 1);
+}
+
+static int qce_skcipher_decrypt(struct skcipher_request *req)
+{
+	return qce_skcipher_crypt(req, 0);
+}
+
+static int qce_skcipher_init(struct crypto_skcipher *tfm)
+{
+	/* take the size without the fallback skcipher_request at the end */
+	crypto_skcipher_set_reqsize(tfm, offsetof(struct qce_cipher_reqctx,
+						  fallback_req));
+	return 0;
+}
+
+static int qce_skcipher_init_fallback(struct crypto_skcipher *tfm)
+{
+	struct qce_cipher_ctx *ctx = crypto_skcipher_ctx(tfm);
+
+	ctx->fallback = crypto_alloc_skcipher(crypto_tfm_alg_name(&tfm->base),
+					      0, CRYPTO_ALG_NEED_FALLBACK);
+	if (IS_ERR(ctx->fallback))
+		return PTR_ERR(ctx->fallback);
+
+	crypto_skcipher_set_reqsize(tfm, sizeof(struct qce_cipher_reqctx) +
+					 crypto_skcipher_reqsize(ctx->fallback));
+	return 0;
+}
+
+static void qce_skcipher_exit(struct crypto_skcipher *tfm)
+{
+	struct qce_cipher_ctx *ctx = crypto_skcipher_ctx(tfm);
+
+	crypto_free_skcipher(ctx->fallback);
+}
+
+struct qce_skcipher_def {
+	unsigned long flags;
+	const char *name;
+	const char *drv_name;
+	unsigned int blocksize;
+	unsigned int chunksize;
+	unsigned int ivsize;
+	unsigned int min_keysize;
+	unsigned int max_keysize;
+};
+
+static const struct qce_skcipher_def skcipher_def[] = {
+	{
+		.flags		= QCE_ALG_AES | QCE_MODE_CBC,
+		.name		= "cbc(aes)",
+		.drv_name	= "cbc-aes-qce",
+		.blocksize	= AES_BLOCK_SIZE,
+		.ivsize		= AES_BLOCK_SIZE,
+		.min_keysize	= AES_MIN_KEY_SIZE,
+		.max_keysize	= AES_MAX_KEY_SIZE,
+	},
+	{
+		.flags		= QCE_ALG_AES | QCE_MODE_CTR,
+		.name		= "ctr(aes)",
+		.drv_name	= "ctr-aes-qce",
+		.blocksize	= 1,
+		.chunksize	= AES_BLOCK_SIZE,
+		.ivsize		= AES_BLOCK_SIZE,
+		.min_keysize	= AES_MIN_KEY_SIZE,
+		.max_keysize	= AES_MAX_KEY_SIZE,
+	},
+	{
+		.flags		= QCE_ALG_AES | QCE_MODE_XTS,
+		.name		= "xts(aes)",
+		.drv_name	= "xts-aes-qce",
+		.blocksize	= AES_BLOCK_SIZE,
+		.ivsize		= AES_BLOCK_SIZE,
+		.min_keysize	= AES_MIN_KEY_SIZE * 2,
+		.max_keysize	= AES_MAX_KEY_SIZE * 2,
+	},
+};
+
+static int qce_skcipher_register_one(const struct qce_skcipher_def *def,
+				       struct qce_device *qce)
+{
+	struct qce_alg_template *tmpl;
+	struct skcipher_alg *alg;
+	int ret;
+
+	tmpl = kzalloc_obj(*tmpl);
+	if (!tmpl)
+		return -ENOMEM;
+
+	alg = &tmpl->alg.skcipher;
+
+	strscpy(alg->base.cra_name, def->name);
+	strscpy(alg->base.cra_driver_name, def->drv_name);
+
+	alg->base.cra_blocksize		= def->blocksize;
+	alg->chunksize			= def->chunksize;
+	alg->ivsize			= def->ivsize;
+	alg->min_keysize		= def->min_keysize;
+	alg->max_keysize		= def->max_keysize;
+	alg->setkey			= qce_skcipher_setkey;
+	alg->encrypt			= qce_skcipher_encrypt;
+	alg->decrypt			= qce_skcipher_decrypt;
+
+	alg->base.cra_priority		= 275;
+	alg->base.cra_flags		= CRYPTO_ALG_ASYNC |
+					  CRYPTO_ALG_ALLOCATES_MEMORY |
+					  CRYPTO_ALG_KERN_DRIVER_ONLY;
+	alg->base.cra_ctxsize		= sizeof(struct qce_cipher_ctx);
+	alg->base.cra_alignmask		= 0;
+	alg->base.cra_module		= THIS_MODULE;
+
+	if (IS_AES(def->flags)) {
+		alg->base.cra_flags    |= CRYPTO_ALG_NEED_FALLBACK;
+		alg->init		= qce_skcipher_init_fallback;
+		alg->exit		= qce_skcipher_exit;
+	} else {
+		alg->init		= qce_skcipher_init;
+	}
+
+	INIT_LIST_HEAD(&tmpl->entry);
+	tmpl->crypto_alg_type = CRYPTO_ALG_TYPE_SKCIPHER;
+	tmpl->alg_flags = def->flags;
+	tmpl->qce = qce;
+
+	ret = crypto_register_skcipher(alg);
+	if (ret) {
+		dev_err(qce->dev, "%s registration failed\n", alg->base.cra_name);
+		kfree(tmpl);
+		return ret;
+	}
+
+	list_add_tail(&tmpl->entry, &skcipher_algs);
+	dev_dbg(qce->dev, "%s is registered\n", alg->base.cra_name);
+	return 0;
+}
+
+static void qce_skcipher_unregister(struct qce_device *qce)
+{
+	struct qce_alg_template *tmpl, *n;
+
+	list_for_each_entry_safe(tmpl, n, &skcipher_algs, entry) {
+		crypto_unregister_skcipher(&tmpl->alg.skcipher);
+		list_del(&tmpl->entry);
+		kfree(tmpl);
+	}
+}
+
+static int qce_skcipher_register(struct qce_device *qce)
+{
+	int ret, i;
+
+	for (i = 0; i < ARRAY_SIZE(skcipher_def); i++) {
+		ret = qce_skcipher_register_one(&skcipher_def[i], qce);
+		if (ret)
+			goto err;
+	}
+
+	return 0;
+err:
+	qce_skcipher_unregister(qce);
+	return ret;
+}
+
+const struct qce_algo_ops skcipher_ops = {
+	.type = CRYPTO_ALG_TYPE_SKCIPHER,
+	.register_algs = qce_skcipher_register,
+	.unregister_algs = qce_skcipher_unregister,
+	.async_req_handle = qce_skcipher_async_req_handle,
+};