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, 306 insertions, 0 deletions

diff --git a/io_uring/fs.c b/io_uring/fs.c
new file mode 100644
index 000000000..26ea841a2
--- /dev/null
+++ b/io_uring/fs.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "../fs/internal.h"
+
+#include "io_uring.h"
+#include "fs.h"
+
+struct io_rename {
+	struct file			*file;
+	int				old_dfd;
+	int				new_dfd;
+	struct delayed_filename		oldpath;
+	struct delayed_filename		newpath;
+	int				flags;
+};
+
+struct io_unlink {
+	struct file			*file;
+	int				dfd;
+	int				flags;
+	struct delayed_filename		filename;
+};
+
+struct io_mkdir {
+	struct file			*file;
+	int				dfd;
+	umode_t				mode;
+	struct delayed_filename		filename;
+};
+
+struct io_link {
+	struct file			*file;
+	int				old_dfd;
+	int				new_dfd;
+	struct delayed_filename		oldpath;
+	struct delayed_filename		newpath;
+	int				flags;
+};
+
+int io_renameat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+	const char __user *oldf, *newf;
+	int err;
+
+	if (sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	ren->old_dfd = READ_ONCE(sqe->fd);
+	oldf = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	newf = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	ren->new_dfd = READ_ONCE(sqe->len);
+	ren->flags = READ_ONCE(sqe->rename_flags);
+
+	err = delayed_getname(&ren->oldpath, oldf);
+	if (unlikely(err))
+		return err;
+
+	err = delayed_getname(&ren->newpath, newf);
+	if (unlikely(err)) {
+		dismiss_delayed_filename(&ren->oldpath);
+		return err;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_renameat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+	CLASS(filename_complete_delayed, old)(&ren->oldpath);
+	CLASS(filename_complete_delayed, new)(&ren->newpath);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_renameat2(ren->old_dfd, old,
+				 ren->new_dfd, new, ren->flags);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_renameat_cleanup(struct io_kiocb *req)
+{
+	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename);
+
+	dismiss_delayed_filename(&ren->oldpath);
+	dismiss_delayed_filename(&ren->newpath);
+}
+
+int io_unlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink);
+	const char __user *fname;
+	int err;
+
+	if (sqe->off || sqe->len || sqe->buf_index || sqe->splice_fd_in ||
+	    sqe->addr3 || sqe->__pad2[0])
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	un->dfd = READ_ONCE(sqe->fd);
+
+	un->flags = READ_ONCE(sqe->unlink_flags);
+	if (un->flags & ~AT_REMOVEDIR)
+		return -EINVAL;
+
+	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	err = delayed_getname(&un->filename, fname);
+	if (unlikely(err))
+		return err;
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_unlinkat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink);
+	CLASS(filename_complete_delayed, name)(&un->filename);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	if (un->flags & AT_REMOVEDIR)
+		ret = filename_rmdir(un->dfd, name);
+	else
+		ret = filename_unlinkat(un->dfd, name);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_unlinkat_cleanup(struct io_kiocb *req)
+{
+	struct io_unlink *ul = io_kiocb_to_cmd(req, struct io_unlink);
+
+	dismiss_delayed_filename(&ul->filename);
+}
+
+int io_mkdirat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir);
+	const char __user *fname;
+	int err;
+
+	if (sqe->off || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	mkd->dfd = READ_ONCE(sqe->fd);
+	mkd->mode = READ_ONCE(sqe->len);
+
+	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	err = delayed_getname(&mkd->filename, fname);
+	if (unlikely(err))
+		return err;
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_mkdirat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir);
+	CLASS(filename_complete_delayed, name)(&mkd->filename);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_mkdirat(mkd->dfd, name, mkd->mode);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_mkdirat_cleanup(struct io_kiocb *req)
+{
+	struct io_mkdir *md = io_kiocb_to_cmd(req, struct io_mkdir);
+
+	dismiss_delayed_filename(&md->filename);
+}
+
+int io_symlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
+	const char __user *oldpath, *newpath;
+	int err;
+
+	if (sqe->len || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	sl->new_dfd = READ_ONCE(sqe->fd);
+	oldpath = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	newpath = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+
+	err = delayed_getname(&sl->oldpath, oldpath);
+	if (unlikely(err))
+		return err;
+
+	err = delayed_getname(&sl->newpath, newpath);
+	if (unlikely(err)) {
+		dismiss_delayed_filename(&sl->oldpath);
+		return err;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_symlinkat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
+	CLASS(filename_complete_delayed, old)(&sl->oldpath);
+	CLASS(filename_complete_delayed, new)(&sl->newpath);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_symlinkat(old, sl->new_dfd, new);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_linkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link);
+	const char __user *oldf, *newf;
+	int err;
+
+	if (sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	lnk->old_dfd = READ_ONCE(sqe->fd);
+	lnk->new_dfd = READ_ONCE(sqe->len);
+	oldf = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	newf = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	lnk->flags = READ_ONCE(sqe->hardlink_flags);
+
+	err = delayed_getname_uflags(&lnk->oldpath, oldf, lnk->flags);
+	if (unlikely(err))
+		return err;
+
+	err = delayed_getname(&lnk->newpath, newf);
+	if (unlikely(err)) {
+		dismiss_delayed_filename(&lnk->oldpath);
+		return err;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_linkat(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link);
+	CLASS(filename_complete_delayed, old)(&lnk->oldpath);
+	CLASS(filename_complete_delayed, new)(&lnk->newpath);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_linkat(lnk->old_dfd, old, lnk->new_dfd, new, lnk->flags);
+
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_link_cleanup(struct io_kiocb *req)
+{
+	struct io_link *sl = io_kiocb_to_cmd(req, struct io_link);
+
+	dismiss_delayed_filename(&sl->oldpath);
+	dismiss_delayed_filename(&sl->newpath);
+}