From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration 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 Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- drivers/char/tpm/tpm-dev-common.c | 290 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 290 insertions(+) create mode 100644 drivers/char/tpm/tpm-dev-common.c (limited to 'drivers/char/tpm/tpm-dev-common.c') diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c new file mode 100644 index 000000000..f942c0c8e --- /dev/null +++ b/drivers/char/tpm/tpm-dev-common.c @@ -0,0 +1,290 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2004 IBM Corporation + * Authors: + * Leendert van Doorn + * Dave Safford + * Reiner Sailer + * Kylene Hall + * + * Copyright (C) 2013 Obsidian Research Corp + * Jason Gunthorpe + * + * Device file system interface to the TPM + */ +#include +#include +#include +#include +#include "tpm.h" +#include "tpm-dev.h" + +static struct workqueue_struct *tpm_dev_wq; + +static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space, + u8 *buf, size_t bufsiz) +{ + struct tpm_header *header = (void *)buf; + ssize_t ret, len; + + if (chip->flags & TPM_CHIP_FLAG_TPM2) + tpm2_end_auth_session(chip); + + ret = tpm2_prepare_space(chip, space, buf, bufsiz); + /* If the command is not implemented by the TPM, synthesize a + * response with a TPM2_RC_COMMAND_CODE return for user-space. + */ + if (ret == -EOPNOTSUPP) { + header->length = cpu_to_be32(sizeof(*header)); + header->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS); + header->return_code = cpu_to_be32(TPM2_RC_COMMAND_CODE | + TSS2_RESMGR_TPM_RC_LAYER); + ret = sizeof(*header); + } + if (ret) + goto out_rc; + + len = tpm_transmit(chip, buf, bufsiz); + if (len < 0) + ret = len; + + if (!ret) + ret = tpm2_commit_space(chip, space, buf, &len); + else + tpm2_flush_space(chip); + +out_rc: + return ret ? ret : len; +} + +static void tpm_dev_async_work(struct work_struct *work) +{ + struct file_priv *priv = + container_of(work, struct file_priv, async_work); + ssize_t ret; + + mutex_lock(&priv->buffer_mutex); + priv->command_enqueued = false; + ret = tpm_try_get_ops(priv->chip); + if (ret) { + priv->response_length = ret; + goto out; + } + + ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer, + sizeof(priv->data_buffer)); + tpm_put_ops(priv->chip); + + /* + * If ret is > 0 then tpm_dev_transmit returned the size of the + * response. If ret is < 0 then tpm_dev_transmit failed and + * returned an error code. + */ + if (ret != 0) { + priv->response_length = ret; + mod_timer(&priv->user_read_timer, jiffies + (120 * HZ)); + } +out: + mutex_unlock(&priv->buffer_mutex); + wake_up_interruptible(&priv->async_wait); +} + +static void user_reader_timeout(struct timer_list *t) +{ + struct file_priv *priv = timer_container_of(priv, t, user_read_timer); + + pr_warn("TPM user space timeout is deprecated (pid=%d)\n", + task_tgid_nr(current)); + + schedule_work(&priv->timeout_work); +} + +static void tpm_timeout_work(struct work_struct *work) +{ + struct file_priv *priv = container_of(work, struct file_priv, + timeout_work); + + mutex_lock(&priv->buffer_mutex); + priv->response_read = true; + priv->response_length = 0; + memset(priv->data_buffer, 0, sizeof(priv->data_buffer)); + mutex_unlock(&priv->buffer_mutex); + wake_up_interruptible(&priv->async_wait); +} + +void tpm_common_open(struct file *file, struct tpm_chip *chip, + struct file_priv *priv, struct tpm_space *space) +{ + priv->chip = chip; + priv->space = space; + priv->response_read = true; + + mutex_init(&priv->buffer_mutex); + timer_setup(&priv->user_read_timer, user_reader_timeout, 0); + INIT_WORK(&priv->timeout_work, tpm_timeout_work); + INIT_WORK(&priv->async_work, tpm_dev_async_work); + init_waitqueue_head(&priv->async_wait); + file->private_data = priv; +} + +ssize_t tpm_common_read(struct file *file, char __user *buf, + size_t size, loff_t *off) +{ + struct file_priv *priv = file->private_data; + ssize_t ret_size = 0; + int rc; + + mutex_lock(&priv->buffer_mutex); + + if (priv->response_length) { + priv->response_read = true; + + ret_size = min_t(ssize_t, size, priv->response_length); + if (ret_size <= 0) { + priv->response_length = 0; + goto out; + } + + rc = copy_to_user(buf, priv->data_buffer + *off, ret_size); + if (rc) { + memset(priv->data_buffer, 0, TPM_BUFSIZE); + priv->response_length = 0; + ret_size = -EFAULT; + } else { + memset(priv->data_buffer + *off, 0, ret_size); + priv->response_length -= ret_size; + *off += ret_size; + } + } + +out: + if (!priv->response_length) { + *off = 0; + timer_delete_sync(&priv->user_read_timer); + flush_work(&priv->timeout_work); + } + mutex_unlock(&priv->buffer_mutex); + return ret_size; +} + +ssize_t tpm_common_write(struct file *file, const char __user *buf, + size_t size, loff_t *off) +{ + struct file_priv *priv = file->private_data; + int ret = 0; + + if (size > TPM_BUFSIZE) + return -E2BIG; + + mutex_lock(&priv->buffer_mutex); + + /* Cannot perform a write until the read has cleared either via + * tpm_read or a user_read_timer timeout. This also prevents split + * buffered writes from blocking here. + */ + if ((!priv->response_read && priv->response_length) || + priv->command_enqueued) { + ret = -EBUSY; + goto out; + } + + if (copy_from_user(priv->data_buffer, buf, size)) { + ret = -EFAULT; + goto out; + } + + if (size < 6 || + size < be32_to_cpu(*((__be32 *)(priv->data_buffer + 2)))) { + ret = -EINVAL; + goto out; + } + + priv->response_length = 0; + priv->response_read = false; + *off = 0; + + /* + * If in nonblocking mode schedule an async job to send + * the command return the size. + * In case of error the err code will be returned in + * the subsequent read call. + */ + if (file->f_flags & O_NONBLOCK) { + priv->command_enqueued = true; + queue_work(tpm_dev_wq, &priv->async_work); + mutex_unlock(&priv->buffer_mutex); + return size; + } + + /* atomic tpm command send and result receive. We only hold the ops + * lock during this period so that the tpm can be unregistered even if + * the char dev is held open. + */ + if (tpm_try_get_ops(priv->chip)) { + ret = -EPIPE; + goto out; + } + + ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer, + sizeof(priv->data_buffer)); + tpm_put_ops(priv->chip); + + if (ret > 0) { + priv->response_length = ret; + mod_timer(&priv->user_read_timer, jiffies + (120 * HZ)); + ret = size; + } +out: + mutex_unlock(&priv->buffer_mutex); + return ret; +} + +__poll_t tpm_common_poll(struct file *file, poll_table *wait) +{ + struct file_priv *priv = file->private_data; + __poll_t mask = 0; + + poll_wait(file, &priv->async_wait, wait); + mutex_lock(&priv->buffer_mutex); + + /* + * The response_length indicates if there is still response + * (or part of it) to be consumed. Partial reads decrease it + * by the number of bytes read, and write resets it the zero. + */ + if (priv->response_length) + mask = EPOLLIN | EPOLLRDNORM; + else + mask = EPOLLOUT | EPOLLWRNORM; + + mutex_unlock(&priv->buffer_mutex); + return mask; +} + +/* + * Called on file close + */ +void tpm_common_release(struct file *file, struct file_priv *priv) +{ + flush_work(&priv->async_work); + timer_delete_sync(&priv->user_read_timer); + flush_work(&priv->timeout_work); + file->private_data = NULL; + priv->response_length = 0; +} + +int __init tpm_dev_common_init(void) +{ + tpm_dev_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM | WQ_PERCPU, + 0); + + return !tpm_dev_wq ? -ENOMEM : 0; +} + +void __exit tpm_dev_common_exit(void) +{ + if (tpm_dev_wq) { + destroy_workqueue(tpm_dev_wq); + tpm_dev_wq = NULL; + } +} -- cgit v1.3.1