When convert-in-place=true, the guest_memfd instance created by memory-backend-memfd (when guest-memfd=on option is specified) should also be used internally for private memory.
Do this by dup()'ing the guest_memfd FD provided by the backend so the separate cleanup paths for shared vs. private FDs can be managed in the same way they are currently for convert-in-place=false (where shared memory must come from something other than guest_memfd). Introduce a new RAM_GUEST_MEMFD_SHARED flag that can be used to limit this dup()'ing to specific backend types like memory-backend-memfd. Signed-off-by: Michael Roth <[email protected]> --- backends/hostmem-memfd.c | 1 + include/system/memory.h | 3 +++ system/physmem.c | 48 +++++++++++++++++++++++++++++++++++++--- 3 files changed, 49 insertions(+), 3 deletions(-) diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c index 6576331441..a9759e682b 100644 --- a/backends/hostmem-memfd.c +++ b/backends/hostmem-memfd.c @@ -89,6 +89,7 @@ have_fd: backend->aligned = true; ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE; ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; + ram_flags |= RAM_GUEST_MEMFD_SHARED; ram_flags |= backend->guest_memfd_private ? RAM_GUEST_MEMFD_PRIVATE : 0; return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name, backend->size, ram_flags, fd, 0, errp); diff --git a/include/system/memory.h b/include/system/memory.h index 027ca81bd2..81616bfe39 100644 --- a/include/system/memory.h +++ b/include/system/memory.h @@ -274,6 +274,9 @@ typedef struct IOMMUTLBEvent { */ #define RAM_PRIVATE (1 << 13) +/* RAM can be shared that has kvm guest memfd backend */ +#define RAM_GUEST_MEMFD_SHARED (1 << 14) + static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, IOMMUNotifierFlag flags, hwaddr start, hwaddr end, diff --git a/system/physmem.c b/system/physmem.c index 991f7bb815..d77e6fccb5 100644 --- a/system/physmem.c +++ b/system/physmem.c @@ -59,6 +59,7 @@ #include "system/hostmem.h" #include "system/hw_accel.h" #include "system/xen-mapcache.h" +#include "system/confidential-guest-support.h" #include "trace.h" #ifdef CONFIG_FALLOCATE_PUNCH_HOLE @@ -2185,6 +2186,8 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) if (new_block->flags & RAM_GUEST_MEMFD_PRIVATE) { int ret; + assert(current_machine->cgs); + if (!kvm_enabled()) { error_setg(errp, "cannot set up private guest memory for %s: KVM required", object_get_typename(OBJECT(current_machine->cgs))); @@ -2208,10 +2211,43 @@ static void ram_block_add(RAMBlock *new_block, Error **errp) goto out_free; } - new_block->guest_memfd_private = - kvm_create_guest_memfd_private(new_block->max_length, errp); + /* + * If both shared/private memory are handled by guest_memfd, make sure + * to re-use the guest_memfd inode that should have already been created + * for handling shared memory. + */ + if (machine_require_guest_memfd_convert_in_place(current_machine)) { + if (!(new_block->flags & RAM_GUEST_MEMFD_SHARED)) { + error_setg(errp, "configured memory backend is not compatible" + " with in-place conversion"); + qemu_mutex_unlock_ramlist(); + goto out_free; + } + assert(new_block->fd >= 0); + + /* + * Current logic calculates guest_memfd_offset on the assumption + * that offset 0 corresponds to the first GPA that is backed by the + * RAM block/backend. For cases where the guest_memfd is only used + * for private memory and created internally as-needed this is + * always the case, but when re-using a guest_memfd that's also + * usable for shared memory (e.g. via memory-backend-guest-memfd) + * it's possible that guest_memfd might be mmap()'d starting at some + * non-zero offset. For now, this isn't a reachable condition, but + * assert this in case this ever changes and the logic needs to be + * updated to account for this. + */ + assert(new_block->fd_offset == 0); + + new_block->guest_memfd_private = qemu_dup(new_block->fd); + } else { + new_block->guest_memfd_private = + kvm_create_guest_memfd_private(new_block->max_length, errp); + } + if (new_block->guest_memfd_private < 0) { qemu_mutex_unlock_ramlist(); + error_setg(errp, "failed to create guest_memfd instance."); goto out_free; } @@ -2320,7 +2356,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, ram_addr_t max_size, assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE | RAM_PROTECTED | RAM_NAMED_FILE | RAM_READONLY | RAM_READONLY_FD | RAM_GUEST_MEMFD_PRIVATE | - RAM_RESIZEABLE)) == 0); + RAM_RESIZEABLE | RAM_GUEST_MEMFD_SHARED)) == 0); assert(max_size >= size); if (xen_enabled()) { @@ -2832,6 +2868,12 @@ int ram_block_rebind(Error **errp) { RAMBlock *block; + if (machine_require_guest_memfd_convert_in_place(current_machine)) { + error_setg(errp, + "rebind support is not yet enabled for in-place conversion"); + return -1; + } + qemu_mutex_lock_ramlist(); RAMBLOCK_FOREACH(block) { -- 2.43.0
