Re: [Qemu-devel] [PATCH v10 3/6] tpm: allocate/map buffer for TPM Physical Presence interface

[Juan Quintela]

Marc-André Lureau <address@hidden> wrote:
> Hi
>
> On Fri, Aug 31, 2018 at 7:32 PM Marc-André Lureau
> <address@hidden> wrote:
>>
>> From: Stefan Berger <address@hidden>
>>
>> Implement a virtual memory device for the TPM Physical Presence interface.
>> The memory is located at 0xFED45000 and used by ACPI to send messages to the
>> firmware (BIOS) and by the firmware to provide parameters for each one of
>> the supported codes.
>>
>> This interface should be used by all TPM devices on x86 and can be
>> added by calling tpm_ppi_init_io().
>>
>> Note: bios_linker cannot be used to allocate the PPI memory region,
>> since the reserved memory should stay stable across reboots, and might
>> be needed before the ACPI tables are installed.
>>
>> Signed-off-by: Stefan Berger <address@hidden>
>> Signed-off-by: Marc-André Lureau <address@hidden>
>> Reviewed-by: Igor Mammedov <address@hidden>


....

>> + */
>> +#define TPM_PPI_ADDR_SIZE           0x400
>> +#define TPM_PPI_ADDR_BASE           0xFED45000

> There is a (new) issue with the PPI ram region:
>
> READ of size 32 at 0x61d000090480 thread T6
>     #0 0x5622bd8de0f4 in buffer_zero_avx2
> /home/elmarco/src/qq/util/bufferiszero.c:169
>     #1 0x5622bd8de899 in select_accel_fn
> /home/elmarco/src/qq/util/bufferiszero.c:282
>     #2 0x5622bd8de8f1 in buffer_is_zero
> /home/elmarco/src/qq/util/bufferiszero.c:309
>     #3 0x5622bc209f94 in is_zero_range /home/elmarco/src/qq/migration/ram.c:82
>     #4 0x5622bc21938d in save_zero_page_to_file
> /home/elmarco/src/qq/migration/ram.c:1694
>     #5 0x5622bc219452 in save_zero_page
> /home/elmarco/src/qq/migration/ram.c:1713
>     #6 0x5622bc21db67 in ram_save_target_page
> /home/elmarco/src/qq/migration/ram.c:2289
>     #7 0x5622bc21e13e in ram_save_host_page
> /home/elmarco/src/qq/migration/ram.c:2351
>     #8 0x5622bc21ea3a in ram_find_and_save_block
> /home/elmarco/src/qq/migration/ram.c:2413
>     #9 0x5622bc223b5d in ram_save_iterate
> /home/elmarco/src/qq/migration/ram.c:3193
>     #10 0x5622bd16f544 in qemu_savevm_state_iterate
> /home/elmarco/src/qq/migration/savevm.c:1103
>     #11 0x5622bd157e75 in migration_iteration_run
> /home/elmarco/src/qq/migration/migration.c:2897
>     #12 0x5622bd15892e in migration_thread
> /home/elmarco/src/qq/migration/migration.c:3018
>     #13 0x5622bd902f31 in qemu_thread_start
> /home/elmarco/src/qq/util/qemu-thread-posix.c:504
>     #14 0x7f42f0ef4593 in start_thread (/lib64/libpthread.so.0+0x7593)
>     #15 0x7f42f0c280de in clone (/lib64/libc.so.6+0xfa0de)
> 0x61d000090490 is located 0 bytes to the right of 2064-byte region
> [0x61d00008fc80,0x61d000090490)
>
> migration code is assuming RAM is multiple of TARGET_PAGE_SIZE.

Physical RAM is multiple of TARGET_PAGE_SIZE O:-)
That assumtion is held in too many places, if you can change the size to
be multiple of page size, that would be greate.

> Should the migration code be fixed, or should the TPM code allocate
> ram differently?

Migration people (i.e. me) would preffer that you fix the TPM
allocation.  Or you can decide that this is *not* RAM.  The unit of
transfer for migrate ram is ram pages, a.k.a. TARGET_PAGE_SIZE.

> In all case, I think the migration code should either be fixed or have
> an assert.

An assert for sure.

Fixed .... Do we have real devices that put ram regions that are smaller
than page size?

Later, Juan.