Re: [Qemu-devel] [qemu-s390x] [PATCH v8 05/13] s390-ccw: move auxiliary IPL data to separate location

[Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>]

On 22.02.2018 05:40, Thomas Huth wrote:
> On 21.02.2018 20:35, Collin L. Walling wrote:
>> The s390-ccw firmware needs some information in support of the
>> boot process which is not available on the native machine.
>> Examples are the netboot firmware load address and now the
>> boot menu parameters.
>>
>> While storing that data in unused fields of the IPL parameter block
>> works, that approach could create problems if the parameter block
>> definition should change in the future. Because then a guest could
>> overwrite these fields using the set IPLB diagnose.
>>
>> In fact the data in question is of more global nature and not really
>> tied to an IPL device, so separating it is rather logical.
>>
>> This commit introduces a new structure to hold firmware relevant
>> IPL parameters set by QEMU. The data is stored at location 204 (dec)
>> and can contain up to 7 32-bit words. This area is available to
>> programming in the z/Architecture Principles of Operation and
>> can thus safely be used by the firmware until the IPL has completed.
>>
>> Signed-off-by: Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>
>> Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com>
>> ---
>>  hw/s390x/ipl.c          | 18 +++++++++++++++++-
>>  hw/s390x/ipl.h          | 25 +++++++++++++++++++++++--
>>  pc-bios/s390-ccw/iplb.h | 18 ++++++++++++++++--
>>  pc-bios/s390-ccw/main.c |  6 +++++-
>>  4 files changed, 61 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
>> index 0d06fc1..79f5a58 100644
>> --- a/hw/s390x/ipl.c
>> +++ b/hw/s390x/ipl.c
>> @@ -399,6 +399,21 @@ void s390_reipl_request(void)
>>      qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
>>  }
>>  
>> +static void s390_ipl_prepare_qipl(S390CPU *cpu)
>> +{
>> +    S390IPLState *ipl = get_ipl_device();
>> +    uint8_t *addr;
>> +    uint64_t len = 4096;
>> +
>> +    addr = cpu_physical_memory_map(cpu->env.psa, &len, 1);
>> +    if (!addr || len < QIPL_ADDRESS + sizeof(QemuIplParameters)) {
>> +        error_report("Cannot set QEMU IPL parameters");
>> +        return;
>> +    }
>> +    memcpy(addr + QIPL_ADDRESS, &ipl->qipl, sizeof(QemuIplParameters));
>> +    cpu_physical_memory_unmap(addr, len, 1, len);
>> +}
>> +
>>  void s390_ipl_prepare_cpu(S390CPU *cpu)
>>  {
>>      S390IPLState *ipl = get_ipl_device();
>> @@ -418,8 +433,9 @@ void s390_ipl_prepare_cpu(S390CPU *cpu)
>>              error_report_err(err);
>>              vm_stop(RUN_STATE_INTERNAL_ERROR);
>>          }
>> -        ipl->iplb.ccw.netboot_start_addr = cpu_to_be64(ipl->start_addr);
>> +        ipl->qipl.netboot_start_addr = cpu_to_be64(ipl->start_addr);
>>      }
>> +    s390_ipl_prepare_qipl(cpu);
>>  }
>>  
>>  static void s390_ipl_reset(DeviceState *dev)
>> diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
>> index 8a705e0..08926a3 100644
>> --- a/hw/s390x/ipl.h
>> +++ b/hw/s390x/ipl.h
>> @@ -16,8 +16,7 @@
>>  #include "cpu.h"
>>  
>>  struct IplBlockCcw {
>> -    uint64_t netboot_start_addr;
>> -    uint8_t  reserved0[77];
>> +    uint8_t  reserved0[85];
>>      uint8_t  ssid;
>>      uint16_t devno;
>>      uint8_t  vm_flags;
>> @@ -90,6 +89,27 @@ void s390_ipl_prepare_cpu(S390CPU *cpu);
>>  IplParameterBlock *s390_ipl_get_iplb(void);
>>  void s390_reipl_request(void);
>>  
>> +#define QIPL_ADDRESS  0xcc
>> +
>> +/*
>> + * The QEMU IPL Parameters will be stored at absolute address
>> + * 204 (0xcc) which means it is 32-bit word aligned but not
>> + * double-word aligned.
>> + * Placement of data fields in this area must account for
>> + * their alignment needs. E.g., netboot_start_address must
>> + * have an offset of n * 8 bytes within the struct in order
>> + * to keep it double-word aligned.
> 
> Should that rather be "4 + n * 8" instead of "n * 8" ?
I wonder if I ever get that comment right. You're correct of course.
> 
> Apart from that, patch looks good to me now, so once you've fixed the
> comment (if necessary):
> 
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> 


-- 
Regards,
 Viktor Mihajlovski