Re: [PATCH] acpi: Set maximum size to 64k for "etc/acpi/rsdp" blob

[Feng Sun]

Igor Mammedov <imammedo@redhat.com> 于2023年1月24日周二 18:30写道：
>
> On Tue, 17 Jan 2023 19:15:21 +0800
> Sun Feng <loyou85@gmail.com> wrote:
>
> > Migrate from aarch64 host with PAGE_SIZE 64k to 4k failed with following 
> > errors:
> >
> > qmp_cmd_name: migrate-incoming, arguments: {"uri": "tcp:[::]:49152"}
> > {"timestamp": {"seconds": 1673922775, "microseconds": 534702}, "event": 
> > "MIGRATION", "data": {"status": "setup"}}
> > {"timestamp": {"seconds": 1673922776, "microseconds": 53003}, "event": 
> > "MIGRATION", "data": {"status": "active"}}
> > 2023-01-17T02:32:56.058827Z qemu-system-aarch64: Length too large: 
> > /rom@etc/acpi/rsdp: 0x10000 > 0x1000: Invalid argument
>
> this should mention/explain why it's happening.
>
> i.e we now have 4k limit for RSDP, but then source somehow managed to start 
> with 64k
> allocated to for RSDP. It looks like limit isn't working as expected to me.

4k limit should be romsize limit. I can see Rom '/rom@etc/acpi/rsdp'
with romsize:4096, datasize:36.
RAMBlock's used_length is set with datasize aligned to PAGE_SIZE, so
it become 64k when PAGE_SIZE is 64k.
```
static
RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
                                  void (*resized)(const char*,
                                                  uint64_t length,
                                                  void *host),
                                  void *host, uint32_t ram_flags,
                                  MemoryRegion *mr, Error **errp)
{
    RAMBlock *new_block;
    Error *local_err = NULL;

    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
                          RAM_NORESERVE)) == 0);
    assert(!host ^ (ram_flags & RAM_PREALLOC));

    size = HOST_PAGE_ALIGN(size);
    max_size = HOST_PAGE_ALIGN(max_size);
    new_block = g_malloc0(sizeof(*new_block));
    new_block->mr = mr;
    new_block->resized = resized;
    new_block->used_length = size;
```
So when migrate to 4k PAGE_SIZE, it will report the errors.

ramblock information for PAGE_SIZE 64k and 4k.
```
# getconf PAGE_SIZE
65536
# virsh qemu-monitor-command testvm --hmp 'info ramblock'
              Block Name    PSize              Offset
Used              Total
           mach-virt.ram   64 KiB  0x0000000000000000
0x0000000040000000 0x0000000040000000
             virt.flash0   64 KiB  0x0000000040000000
0x0000000004000000 0x0000000004000000
             virt.flash1   64 KiB  0x0000000044000000
0x0000000004000000 0x0000000004000000
    /rom@etc/acpi/tables   64 KiB  0x0000000048040000
0x0000000000020000 0x0000000000200000
0000:00:01.2:00.0/virtio-net-pci.rom   64 KiB  0x0000000048000000
0x0000000000040000 0x0000000000040000
   /rom@etc/table-loader   64 KiB  0x0000000048240000
0x0000000000010000 0x0000000000010000
      /rom@etc/acpi/rsdp   64 KiB  0x0000000048280000
0x0000000000010000 0x0000000000010000

# getconf PAGE_SIZE
4096
# virsh qemu-monitor-command testvm --hmp 'info ramblock'
              Block Name    PSize              Offset
Used              Total
           mach-virt.ram    4 KiB  0x0000000000000000
0x0000000800000000 0x0000000800000000
             virt.flash0    4 KiB  0x0000000800000000
0x0000000004000000 0x0000000004000000
             virt.flash1    4 KiB  0x0000000804000000
0x0000000004000000 0x0000000004000000
    /rom@etc/acpi/tables    4 KiB  0x0000000808000000
0x0000000000020000 0x0000000000200000
   /rom@etc/table-loader    4 KiB  0x0000000808200000
0x0000000000001000 0x0000000000010000
      /rom@etc/acpi/rsdp    4 KiB  0x0000000808240000
0x0000000000001000 0x0000000000001000
```

-- 
Best wishes!