On Tue, Apr 25, 2023 at 01:56:03PM +0300, Vladimir Sementsov-Ogievskiy wrote: > On incoming migration we have the following sequence to load option > ROM: > > 1. On device realize we do normal load ROM from the file > > 2. Than, on incoming migration we rewrite ROM from the incoming RAM > block. If sizes mismatch we fail. > > This is not ideal when we migrate to updated distribution: we have to > keep old ROM files in new distribution and be careful around romfile > property to load correct ROM file. Which is loaded actually just to > allocate the ROM with correct length. > > Note, that romsize property doesn't really help: if we try to specify > it when default romfile is larger, it fails with something like: > > romfile "efi-virtio.rom" (160768 bytes) is too large for ROM size 65536 > > This commit brings new behavior for romfile="",romsize=SIZE combination > of options. Current behavior is just ignore romsize and not load or > create any ROM. > > Let's instead preallocate ROM, not loading any file. This way we can > migrate old vm to new environment not thinking about ROM files on > destination host: > > 1. specify romfile="",romsize=SIZE on target, with correct SIZE > (actually, size of romfile on source aligned up to power of two, or > just original romsize option on source) > > 2. On device realize we just preallocate ROM, and not load any file > > 3. On incoming migration ROM is filled from the migration stream > > As a bonus we avoid extra reading from ROM file on target. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
why is this a bad idea: - on source presumably user overrides romfile - we have a general rule that source and destination flags must match I propose instead to ignore romfile if qemu is incoming migration and romsize has been specified. > --- > hw/pci/pci.c | 76 +++++++++++++++++++++++++++++----------------------- > 1 file changed, 43 insertions(+), 33 deletions(-) > > diff --git a/hw/pci/pci.c b/hw/pci/pci.c > index a442f8fce1..039e762b66 100644 > --- a/hw/pci/pci.c > +++ b/hw/pci/pci.c > @@ -2293,17 +2293,21 @@ static void pci_add_option_rom(PCIDevice *pdev, bool > is_default_rom, > { > int64_t size; > g_autofree char *path = NULL; > - void *ptr; > char name[32]; > const VMStateDescription *vmsd; > + bool load_file; > > if (!pdev->romfile) { > return; > } > - if (strlen(pdev->romfile) == 0) { > + > + load_file = strlen(pdev->romfile) > 0; > + if (!load_file && pdev->romsize == -1) { > return; > } > > + assert(load_file || !is_default_rom); > + > if (!pdev->rom_bar) { > /* > * Load rom via fw_cfg instead of creating a rom bar, > @@ -2329,32 +2333,35 @@ static void pci_add_option_rom(PCIDevice *pdev, bool > is_default_rom, > return; > } > > - path = qemu_find_file(QEMU_FILE_TYPE_BIOS, pdev->romfile); > - if (path == NULL) { > - path = g_strdup(pdev->romfile); > - } > + if (load_file) { > + path = qemu_find_file(QEMU_FILE_TYPE_BIOS, pdev->romfile); > + if (path == NULL) { > + path = g_strdup(pdev->romfile); > + } > > - size = get_image_size(path); > - if (size < 0) { > - error_setg(errp, "failed to find romfile \"%s\"", pdev->romfile); > - return; > - } else if (size == 0) { > - error_setg(errp, "romfile \"%s\" is empty", pdev->romfile); > - return; > - } else if (size > 2 * GiB) { > - error_setg(errp, "romfile \"%s\" too large (size cannot exceed 2 > GiB)", > - pdev->romfile); > - return; > - } > - if (pdev->romsize != -1) { > - if (size > pdev->romsize) { > - error_setg(errp, "romfile \"%s\" (%u bytes) " > - "is too large for ROM size %u", > - pdev->romfile, (uint32_t)size, pdev->romsize); > + size = get_image_size(path); > + if (size < 0) { > + error_setg(errp, "failed to find romfile \"%s\"", pdev->romfile); > + return; > + } else if (size == 0) { > + error_setg(errp, "romfile \"%s\" is empty", pdev->romfile); > + return; > + } else if (size > 2 * GiB) { > + error_setg(errp, > + "romfile \"%s\" too large (size cannot exceed 2 GiB)", > + pdev->romfile); > return; > } > - } else { > - pdev->romsize = pow2ceil(size); > + if (pdev->romsize != -1) { > + if (size > pdev->romsize) { > + error_setg(errp, "romfile \"%s\" (%u bytes) " > + "is too large for ROM size %u", > + pdev->romfile, (uint32_t)size, pdev->romsize); > + return; > + } > + } else { > + pdev->romsize = pow2ceil(size); > + } > } > > vmsd = qdev_get_vmsd(DEVICE(pdev)); > @@ -2365,15 +2372,18 @@ static void pci_add_option_rom(PCIDevice *pdev, bool > is_default_rom, > memory_region_init_rom(&pdev->rom, OBJECT(pdev), name, pdev->romsize, > &error_fatal); > > - ptr = memory_region_get_ram_ptr(&pdev->rom); > - if (load_image_size(path, ptr, size) < 0) { > - error_setg(errp, "failed to load romfile \"%s\"", pdev->romfile); > - return; > - } > + if (load_file) { > + void *ptr = memory_region_get_ram_ptr(&pdev->rom); > > - if (is_default_rom) { > - /* Only the default rom images will be patched (if needed). */ > - pci_patch_ids(pdev, ptr, size); > + if (load_image_size(path, ptr, size) < 0) { > + error_setg(errp, "failed to load romfile \"%s\"", pdev->romfile); > + return; > + } > + > + if (is_default_rom) { > + /* Only the default rom images will be patched (if needed). */ > + pci_patch_ids(pdev, ptr, size); > + } > } > > pci_register_bar(pdev, PCI_ROM_SLOT, 0, &pdev->rom); > -- > 2.34.1