Re: [Qemu-devel] [qemu-s390x] [PATCH 15/15] s390-bios: Support booting from real dasd device

["Jason J. Herne" <jjherne@linux.ibm.com>]

On 2/20/19 9:52 PM, Eric Farman wrote:
> 
> 
> On 01/29/2019 08:29 AM, Jason J. Herne wrote:
>> Allows guest to boot from a vfio configured real dasd device.
>>
>> Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
>> ---
>>   docs/devel/s390-dasd-ipl.txt | 132 +++++++++++++++++++++++
>>   pc-bios/s390-ccw/Makefile    |   2 +-
>>   pc-bios/s390-ccw/dasd-ipl.c  | 249 +++++++++++++++++++++++++++++++++++++++++++
>>   pc-bios/s390-ccw/dasd-ipl.h  |  16 +++
>>   pc-bios/s390-ccw/main.c      |   4 +
>>   pc-bios/s390-ccw/s390-arch.h |  13 +++
>>   6 files changed, 415 insertions(+), 1 deletion(-)
>>   create mode 100644 docs/devel/s390-dasd-ipl.txt
>>   create mode 100644 pc-bios/s390-ccw/dasd-ipl.c
>>   create mode 100644 pc-bios/s390-ccw/dasd-ipl.h
> 
> ...snip...
> 
>> diff --git a/pc-bios/s390-ccw/dasd-ipl.c b/pc-bios/s390-ccw/dasd-ipl.c
>> new file mode 100644
>> index 0000000..b7ce6d9
>> --- /dev/null
>> +++ b/pc-bios/s390-ccw/dasd-ipl.c
>> @@ -0,0 +1,249 @@
> 
> ...snip...
> 
>> +static void ipl1_fixup(void)
>> +{
>> +    Ccw0 *ccwSeek = (Ccw0 *) 0x08;
>> +    Ccw0 *ccwSearchID = (Ccw0 *) 0x10;
>> +    Ccw0 *ccwSearchTic = (Ccw0 *) 0x18;
>> +    Ccw0 *ccwRead = (Ccw0 *) 0x20;
>> +    CcwSeekData *seekData = (CcwSeekData *) 0x30;
>> +    CcwSearchIdData *searchData = (CcwSearchIdData *) 0x38;
>> +
>> +    /* move IPL1 CCWs to make room for CCWs needed to locate record 2 */
>> +    memcpy(ccwRead, (void *)0x08, 16);
>> +
>> +    /* Disable chaining so we don't TIC to IPL2 channel program */
>> +    ccwRead->chain = 0x00;
>> +
>> +    ccwSeek->cmd_code = CCW_CMD_DASD_SEEK;
>> +    ccwSeek->cda = ptr2u32(seekData);
>> +    ccwSeek->chain = 1;
>> +    ccwSeek->count = sizeof(seekData);
> 
> This needs to be sizeof(*seekData)
> 

Good catch! Thanks. C can be such a pain sometimes. It should do what I WANT... not what I 
SAY :-).

>> +    seekData->reserved = 0x00;
>> +    seekData->cyl = 0x00;
>> +    seekData->head = 0x00;
>> +
>> +    ccwSearchID->cmd_code = CCW_CMD_DASD_SEARCH_ID_EQ;
>> +    ccwSearchID->cda = ptr2u32(searchData);
>> +    ccwSearchID->chain = 1;
>> +    ccwSearchID->count = sizeof(searchData);
> 
> sizeof(*searchData)
> 
> I notice that vfio sees the count for each of these as 8 bytes despite them being packed 
> structs of 6 or 5 bytes.
> 
>> +    searchData->cyl = 0;
>> +    searchData->head = 0;
>> +    searchData->record = 2;
>> +
>> +    /* Go back to Search CCW if correct record not yet found */
>> +    ccwSearchTic->cmd_code = CCW_CMD_TIC;
>> +    ccwSearchTic->cda = ptr2u32(ccwSearchID);
>> +}
>> +
>> +static void run_ipl1(SubChannelId schid)
>> + {
>> +    uint32_t startAddr = 0x08;
>> +
>> +    if (do_cio(schid, startAddr, CCW_FMT0)) {
>> +        panic("dasd-ipl: Failed to run IPL1 channel program");
>> +    }
>> +}
>> +
>> +static void run_ipl2(SubChannelId schid, uint32_t addr)
>> +{
>> +
>> +    if (run_dynamic_ccw_program(schid, addr)) {
>> +        panic("dasd-ipl: Failed to run IPL2 channel program");
>> +    }
>> +}
>> +
>> +static void lpsw(void *psw_addr)
>> +{
>> +    PSWLegacy *pswl = (PSWLegacy *) psw_addr;
>> +
>> +    pswl->mask |= PSW_MASK_EAMODE;   /* Force z-mode */
>> +    pswl->addr |= PSW_MASK_BAMODE;
>> +    asm volatile("  llgtr 0,0\n llgtr 1,1\n"     /* Some OS's expect to be */
>> +                 "  llgtr 2,2\n llgtr 3,3\n"     /* in 32-bit mode. Clear  */
>> +                 "  llgtr 4,4\n llgtr 5,5\n"     /* high part of regs to   */
>> +                 "  llgtr 6,6\n llgtr 7,7\n"     /* avoid messing up       */
>> +                 "  llgtr 8,8\n llgtr 9,9\n"     /* instructions that work */
>> +                 "  llgtr 10,10\n llgtr 11,11\n" /* in both addressing     */
>> +                 "  llgtr 12,12\n llgtr 13,13\n" /* modes, like servc.     */
>> +                 "  llgtr 14,14\n llgtr 15,15\n"
>> +                 "  lpsw %0\n"
>> +                 : : "Q" (*pswl) : "cc");
>> +}
>> +
>> +/*
>> + * Limitations in QEMU's CCW support complicate the IPL process. Details can
>> + * be found in docs/devel/s390-dasd-ipl.txt
>> + */
>> +void dasd_ipl(SubChannelId schid)
>> +{
>> +    uint32_t ipl2_addr;
>> +
>> +    /* Construct Read IPL CCW and run it to read IPL1 from boot disk */
>> +    make_readipl();
>> +    run_readipl(schid);
>> +    ipl2_addr = read_ipl2_addr();
>> +    check_ipl1();
>> +
>> +    /*
>> +     * Fixup IPL1 channel program to account for QEMU limitations, then run it
>> +     * to read IPL2 channel program from boot disk.
>> +     */
>> +    ipl1_fixup();
>> +    run_ipl1(schid);
>> +    check_ipl2(ipl2_addr);
>> +
>> +    /*
>> +     * Run IPL2 channel program to read operating system code from boot disk
>> +     * then transfer control to the guest operating system
>> +     */
>> +    run_ipl2(schid, ipl2_addr);
>> +    lpsw(0);
>> +}
>> diff --git a/pc-bios/s390-ccw/dasd-ipl.h b/pc-bios/s390-ccw/dasd-ipl.h
>> new file mode 100644
>> index 0000000..56bba82
>> --- /dev/null
>> +++ b/pc-bios/s390-ccw/dasd-ipl.h
>> @@ -0,0 +1,16 @@
>> +/*
>> + * S390 IPL (boot) from a real DASD device via vfio framework.
>> + *
>> + * Copyright (c) 2018 Jason J. Herne <jjherne@us.ibm.com>
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or (at
>> + * your option) any later version. See the COPYING file in the top-level
>> + * directory.
>> + */
>> +
>> +#ifndef DASD_IPL_H
>> +#define DASD_IPL_H
>> +
>> +void dasd_ipl(SubChannelId schid);
>> +
>> +#endif /* DASD_IPL_H */
>> diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
>> index 5ee02c3..0a46339 100644
>> --- a/pc-bios/s390-ccw/main.c
>> +++ b/pc-bios/s390-ccw/main.c
>> @@ -13,6 +13,7 @@
>>   #include "s390-ccw.h"
>>   #include "cio.h"
>>   #include "virtio.h"
>> +#include "dasd-ipl.h"
>>   char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
>>   static SubChannelId blk_schid = { .one = 1 };
>> @@ -210,6 +211,9 @@ int main(void)
>>       cutype = cu_type(blk_schid) ;
>>       switch (cutype) {
>> +    case CU_TYPE_DASD_3990:
>> +        dasd_ipl(blk_schid); /* no return */
>> +        break;
>>       case CU_TYPE_VIRTIO:
>>           virtio_setup();
>>           zipl_load(); /* no return */
>> diff --git a/pc-bios/s390-ccw/s390-arch.h b/pc-bios/s390-ccw/s390-arch.h
>> index 47eaa04..0438d42 100644
>> --- a/pc-bios/s390-ccw/s390-arch.h
>> +++ b/pc-bios/s390-ccw/s390-arch.h
>> @@ -97,4 +97,17 @@ typedef struct LowCore {
>>   extern const LowCore *lowcore;
>> +static inline void set_prefix(uint32_t address)
>> +{
>> +    asm volatile("spx %0" : : "m" (address) : "memory");
>> +}
>> +
>> +static inline uint32_t store_prefix(void)
>> +{
>> +    uint32_t address;
>> +
>> +    asm volatile("stpx %0" : "=m" (address));
>> +    return address;
>> +}
>> +
>>   #endif
>>
> 


-- 
-- Jason J. Herne (jjherne@linux.ibm.com)