ivshmem: Implement shm=... with a memory backend
ivshmem has its very own code to create and map shared memory. Replace that with an implicitly created memory backend. Reduces the number of ways we create BAR 2 from three to two. The memory-backend-file is currently available only with CONFIG_LINUX, so this adds a second Linuxism to ivshmem (the other one is eventfd). Should we ever need to make it portable to systems where memory-backend-file can't be made to serve, we could create a memory-backend-shmem that allocates memory with shm_open(). Bonus fix: shared memory files are now created with permissions 0655 instead of 0777. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1458066895-20632-32-git-send-email-armbru@redhat.com>
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@ -26,6 +26,7 @@
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#include "migration/migration.h"
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#include "qemu/error-report.h"
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#include "qemu/event_notifier.h"
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#include "qom/object_interfaces.h"
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#include "sysemu/char.h"
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#include "sysemu/hostmem.h"
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#include "qapi/visitor.h"
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@ -369,31 +370,6 @@ static int check_shm_size(IVShmemState *s, int fd, Error **errp)
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}
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}
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/* create the shared memory BAR when we are not using the server, so we can
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* create the BAR and map the memory immediately */
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static int create_shared_memory_BAR(IVShmemState *s, int fd, uint8_t attr,
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Error **errp)
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{
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void * ptr;
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ptr = mmap(0, s->ivshmem_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
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if (ptr == MAP_FAILED) {
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error_setg_errno(errp, errno, "Failed to mmap shared memory");
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return -1;
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}
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memory_region_init_ram_ptr(&s->ivshmem, OBJECT(s), "ivshmem.bar2",
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s->ivshmem_size, ptr);
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qemu_set_ram_fd(memory_region_get_ram_addr(&s->ivshmem), fd);
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vmstate_register_ram(&s->ivshmem, DEVICE(s));
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memory_region_add_subregion(&s->bar, 0, &s->ivshmem);
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/* region for shared memory */
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pci_register_bar(PCI_DEVICE(s), 2, attr, &s->bar);
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return 0;
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}
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static void ivshmem_add_eventfd(IVShmemState *s, int posn, int i)
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{
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memory_region_add_eventfd(&s->ivshmem_mmio,
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@ -837,6 +813,23 @@ static void ivshmem_write_config(PCIDevice *pdev, uint32_t address,
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}
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}
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static void desugar_shm(IVShmemState *s)
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{
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Object *obj;
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char *path;
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obj = object_new("memory-backend-file");
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path = g_strdup_printf("/dev/shm/%s", s->shmobj);
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object_property_set_str(obj, path, "mem-path", &error_abort);
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g_free(path);
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object_property_set_int(obj, s->ivshmem_size, "size", &error_abort);
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object_property_set_bool(obj, true, "share", &error_abort);
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object_property_add_child(OBJECT(s), "internal-shm-backend", obj,
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&error_abort);
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user_creatable_complete(obj, &error_abort);
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s->hostmem = MEMORY_BACKEND(obj);
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}
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static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
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{
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IVShmemState *s = IVSHMEM(dev);
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@ -915,6 +908,10 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
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attr |= PCI_BASE_ADDRESS_MEM_TYPE_64;
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}
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if (s->shmobj) {
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desugar_shm(s);
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}
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if (s->hostmem != NULL) {
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MemoryRegion *mr;
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@ -925,7 +922,7 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
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vmstate_register_ram(mr, DEVICE(s));
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memory_region_add_subregion(&s->bar, 0, mr);
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pci_register_bar(PCI_DEVICE(s), 2, attr, &s->bar);
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} else if (s->server_chr != NULL) {
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} else {
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IVSHMEM_DPRINTF("using shared memory server (socket = %s)\n",
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s->server_chr->filename);
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@ -952,36 +949,6 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
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error_setg(errp, "failed to initialize interrupts");
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return;
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}
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} else {
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/* just map the file immediately, we're not using a server */
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int fd;
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IVSHMEM_DPRINTF("using shm_open (shm object = %s)\n", s->shmobj);
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/* try opening with O_EXCL and if it succeeds zero the memory
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* by truncating to 0 */
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if ((fd = shm_open(s->shmobj, O_CREAT|O_RDWR|O_EXCL,
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S_IRWXU|S_IRWXG|S_IRWXO)) > 0) {
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/* truncate file to length PCI device's memory */
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if (ftruncate(fd, s->ivshmem_size) != 0) {
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error_report("could not truncate shared file");
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}
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} else if ((fd = shm_open(s->shmobj, O_CREAT|O_RDWR,
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S_IRWXU|S_IRWXG|S_IRWXO)) < 0) {
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error_setg(errp, "could not open shared file");
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return;
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}
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if (check_shm_size(s, fd, errp) == -1) {
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return;
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}
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create_shared_memory_BAR(s, fd, attr, &err);
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if (err) {
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error_propagate(errp, err);
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return;
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}
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}
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if (s->role_val == IVSHMEM_PEER) {
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