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 --- io_uring/query.c | 155 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 155 insertions(+) create mode 100644 io_uring/query.c (limited to 'io_uring/query.c') diff --git a/io_uring/query.c b/io_uring/query.c new file mode 100644 index 000000000..7bce2ec16 --- /dev/null +++ b/io_uring/query.c @@ -0,0 +1,155 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "linux/io_uring/query.h" + +#include "query.h" +#include "io_uring.h" +#include "zcrx.h" + +union io_query_data { + struct io_uring_query_opcode opcodes; + struct io_uring_query_zcrx zcrx; + struct io_uring_query_zcrx_event zcrx_notif; + struct io_uring_query_scq scq; +}; + +#define IO_MAX_QUERY_SIZE sizeof(union io_query_data) +#define IO_MAX_QUERY_ENTRIES 1000 + +static ssize_t io_query_ops(union io_query_data *data) +{ + struct io_uring_query_opcode *e = &data->opcodes; + + e->nr_request_opcodes = IORING_OP_LAST; + e->nr_register_opcodes = IORING_REGISTER_LAST; + e->feature_flags = IORING_FEAT_FLAGS; + e->ring_setup_flags = IORING_SETUP_FLAGS; + e->enter_flags = IORING_ENTER_FLAGS; + e->sqe_flags = SQE_VALID_FLAGS; + e->nr_query_opcodes = __IO_URING_QUERY_MAX; + e->__pad = 0; + return sizeof(*e); +} + +static ssize_t io_query_zcrx(union io_query_data *data) +{ + struct io_uring_query_zcrx *e = &data->zcrx; + + e->register_flags = ZCRX_SUPPORTED_REG_FLAGS; + e->area_flags = IORING_ZCRX_AREA_DMABUF; + e->nr_ctrl_opcodes = __ZCRX_CTRL_LAST; + e->rq_hdr_size = sizeof(struct zcrx_rq_hdr); + e->rq_hdr_alignment = L1_CACHE_BYTES; + e->features = ZCRX_FEATURES; + e->__resv2 = 0; + return sizeof(*e); +} + +static ssize_t io_query_zcrx_notif(union io_query_data *data) +{ + struct io_uring_query_zcrx_event *e = &data->zcrx_notif; + + e->event_flags = ZCRX_EVENT_TYPE_MASK; + e->stats_size = sizeof(struct zcrx_stats); + e->stats_off_alignment = __alignof__(struct zcrx_stats); + e->__resv1 = 0; + memset(&e->__resv2, 0, sizeof(e->__resv2)); + return sizeof(*e); +} + +static ssize_t io_query_scq(union io_query_data *data) +{ + struct io_uring_query_scq *e = &data->scq; + + e->hdr_size = sizeof(struct io_rings); + e->hdr_alignment = SMP_CACHE_BYTES; + return sizeof(*e); +} + +static int io_handle_query_entry(union io_query_data *data, void __user *uhdr, + u64 *next_entry) +{ + struct io_uring_query_hdr hdr; + size_t usize, res_size = 0; + ssize_t ret = -EINVAL; + void __user *udata; + + if (copy_from_user(&hdr, uhdr, sizeof(hdr))) + return -EFAULT; + /* copy_struct_to_user() zeros up to usize bytes */ + if (hdr.size > PAGE_SIZE) + return -E2BIG; + usize = hdr.size; + hdr.size = min(hdr.size, IO_MAX_QUERY_SIZE); + udata = u64_to_user_ptr(hdr.query_data); + + if (hdr.query_op >= __IO_URING_QUERY_MAX) { + ret = -EOPNOTSUPP; + goto out; + } + if (!mem_is_zero(hdr.__resv, sizeof(hdr.__resv)) || hdr.result || !hdr.size) + goto out; + if (copy_from_user(data, udata, hdr.size)) + return -EFAULT; + + switch (hdr.query_op) { + case IO_URING_QUERY_OPCODES: + ret = io_query_ops(data); + break; + case IO_URING_QUERY_ZCRX: + ret = io_query_zcrx(data); + break; + case IO_URING_QUERY_ZCRX_EVENT: + ret = io_query_zcrx_notif(data); + break; + case IO_URING_QUERY_SCQ: + ret = io_query_scq(data); + break; + } + + if (ret >= 0) { + if (WARN_ON_ONCE(ret > IO_MAX_QUERY_SIZE)) + return -EFAULT; + res_size = ret; + ret = 0; + } +out: + hdr.result = ret; + hdr.size = min_t(size_t, usize, res_size); + + if (copy_struct_to_user(udata, usize, data, hdr.size, NULL)) + return -EFAULT; + if (copy_to_user(uhdr, &hdr, sizeof(hdr))) + return -EFAULT; + *next_entry = hdr.next_entry; + return 0; +} + +int io_query(void __user *arg, unsigned nr_args) +{ + union io_query_data entry_buffer; + void __user *uhdr = arg; + int ret, nr = 0; + + memset(&entry_buffer, 0, sizeof(entry_buffer)); + + if (nr_args) + return -EINVAL; + + while (uhdr) { + u64 next_hdr; + + ret = io_handle_query_entry(&entry_buffer, uhdr, &next_hdr); + if (ret) + return ret; + uhdr = u64_to_user_ptr(next_hdr); + + /* Have some limit to avoid a potential cycle */ + if (++nr >= IO_MAX_QUERY_ENTRIES) + return -ERANGE; + if (fatal_signal_pending(current)) + return -EINTR; + cond_resched(); + } + return 0; +} -- cgit v1.3.1