| Message ID | 1552494682-16788-16-git-send-email-jjherne@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | s390: vfio-ccw dasd ipl support | expand |
On 13/03/2019 17.31, 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> > Reviewed-by: Cornelia Huck <cohuck@redhat.com> > --- [...] > diff --git a/docs/devel/s390-dasd-ipl.txt b/docs/devel/s390-dasd-ipl.txt > new file mode 100644 > index 0000000..236428a > --- /dev/null > +++ b/docs/devel/s390-dasd-ipl.txt > @@ -0,0 +1,133 @@ > +***************************** > +***** s390 hardware IPL ***** > +***************************** > + > +The s390 hardware IPL process consists of the following steps. > + > +1. A READ IPL ccw is constructed in memory location 0x0. > + This ccw, by definition, reads the IPL1 record which is located on the disk > + at cylinder 0 track 0 record 1. Note that the chain flag is on in this ccw > + so when it is complete another ccw will be fetched and executed from memory > + location 0x08. > + > +2. Execute the Read IPL ccw at 0x00, thereby reading IPL1 data into 0x00. > + IPL1 data is 24 bytes in length and consists of the following pieces of > + information: [psw][read ccw][tic ccw]. When the machine executes the Read > + IPL ccw it read the 24-bytes of IPL1 to be read into memory starting at > + location 0x0. Then the ccw program at 0x08 which consists of a read > + ccw and a tic ccw is automatically executed because of the chain flag from > + the original READ IPL ccw. The read ccw will read the IPL2 data into memory > + and the TIC (Tranfer In Channel) will transfer control to the channel s/Tranfer/Transfer/ ? [...] > +********************************************************** > +***** How this all pertains to QEMU (and the kernel) ***** > +********************************************************** > + > +In theory we should merely have to do the following to IPL/boot a guest > +operating system from a DASD device: > + > +1. Place a "Read IPL" ccw into memory location 0x0 with chaining bit on. > +2. Execute channel program at 0x0. > +3. LPSW 0x0. > + > +However, our emulation of the machine's channel program logic within the kernel > +is missing one key feature that is required for this process to work: > +non-prefetch of ccw data. > + > +When we start a channel program we pass the channel subsystem parameters via an > +ORB (Operation Request Block). One of those parameters is a prefetch bit. If the > +bit is on then the vfio-ccw kernel driver is allowed to read the entire channel > +program from guest memory before it starts executing it. This means that any > +channel commands that read additional channel commands will not work as expected > +because the newly read commands will only exist in guest memory and NOT within > +the kernel's channel subsystem memory. The kernel vfio-ccw driver currently > +requires this bit to be on for all channel programs. This is a problem because > +the IPL process consists of transferring control from the "Read IPL" ccw > +immediately to the IPL1 channel program that was read by "Read IPL". > + > +Not being able to turn off prefetch will also prevent the TIC at the end of the > +IPL1 channel program from transferring control to the IPL2 channel program. > + > +Lastly, in some cases (the zipl bootloader for example) the IPL2 program also > +tansfers control to another channel program segment immediately after reading it s/tansfers/transfers/ > +from the disk. So we need to be able to handle this case. > + > +************************** > +***** What QEMU does ***** > +************************** > + > +Since we are forced to live with prefetch we cannot use the very simple IPL > +procedure we defined in the preceding section. So we compensate by doing the > +following. > + > +1. Place "Read IPL" ccw into memory location 0x0, but turn off chaining bit. > +2. Execute "Read IPL" at 0x0. > + > + So now IPL1's psw is at 0x0 and IPL1's channel program is at 0x08. > + > +4. Write a custom channel program that will seek to the IPL2 record and then > + execute the READ and TIC ccws from IPL1. Normamly the seek is not required s/Normamly/Normally/ [...] > diff --git a/pc-bios/s390-ccw/dasd-ipl.c b/pc-bios/s390-ccw/dasd-ipl.c > new file mode 100644 > index 0000000..1a44469 > --- /dev/null > +++ b/pc-bios/s390-ccw/dasd-ipl.c > @@ -0,0 +1,249 @@ > +/* > + * S390 IPL (boot) from a real DASD device via vfio framework. > + * > + * Copyright (c) 2019 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. > + */ > + > +#include "libc.h" > +#include "s390-ccw.h" > +#include "s390-arch.h" > +#include "dasd-ipl.h" > +#include "helper.h" > + > +static char prefix_page[PAGE_SIZE * 2] > + __attribute__((__aligned__(PAGE_SIZE * 2))); > + > +static void enable_prefixing(void) > +{ > + memcpy(&prefix_page, (void *)0, 4096); You could use the "lowcore" variable from s390-arch.h here instead of "(void *)0", I guess. > + set_prefix(ptr2u32(&prefix_page)); > +} > + > +static void disable_prefixing(void) > +{ > + set_prefix(0); > + /* Copy io interrupt info back to low core */ > + memcpy((void *)0xB8, prefix_page + 0xB8, 12); Maybe use &lowcore->subchannel_id instead of 0xB8 ? ... not sure whether that's nicer here, though... > +} > + > +static bool is_read_tic_ccw_chain(Ccw0 *ccw) > +{ > + Ccw0 *next_ccw = ccw + 1; > + > + return ((ccw->cmd_code == CCW_CMD_DASD_READ || > + ccw->cmd_code == CCW_CMD_DASD_READ_MT) && > + ccw->chain && next_ccw->cmd_code == CCW_CMD_TIC); > +} > + > +static bool dynamic_cp_fixup(uint32_t ccw_addr, uint32_t *next_cpa) > +{ > + Ccw0 *cur_ccw = (Ccw0 *)(uint64_t)ccw_addr; > + Ccw0 *tic_ccw; > + > + while (true) { > + /* Skip over inline TIC (it might not have the chain bit on) */ > + if (cur_ccw->cmd_code == CCW_CMD_TIC && > + cur_ccw->cda == ptr2u32(cur_ccw) - 8) { > + cur_ccw += 1; > + continue; > + } > + > + if (!cur_ccw->chain) { > + break; > + } > + if (is_read_tic_ccw_chain(cur_ccw)) { > + /* > + * Breaking a chain of CCWs may alter the semantics or even the > + * validity of a channel program. The heuristic implemented below > + * seems to work well in practice for the channel programs > + * generated by zipl. > + */ > + tic_ccw = cur_ccw + 1; > + *next_cpa = tic_ccw->cda; > + cur_ccw->chain = 0; > + return true; > + } > + cur_ccw += 1; > + } > + return false; > +} > + > +static int run_dynamic_ccw_program(SubChannelId schid, uint16_t cutype, > + uint32_t cpa) > +{ > + bool has_next; > + uint32_t next_cpa = 0; > + int rc; > + > + do { > + has_next = dynamic_cp_fixup(cpa, &next_cpa); > + > + print_int("executing ccw chain at ", cpa); > + enable_prefixing(); > + rc = do_cio(schid, cutype, cpa, CCW_FMT0); > + disable_prefixing(); > + > + if (rc) { > + break; > + } > + cpa = next_cpa; > + } while (has_next); > + > + return rc; > +} > + > +static void make_readipl(void) > +{ > + Ccw0 *ccwIplRead = (Ccw0 *)0x00; > + > + /* Create Read IPL ccw at address 0 */ > + ccwIplRead->cmd_code = CCW_CMD_READ_IPL; > + ccwIplRead->cda = 0x00; /* Read into address 0x00 in main memory */ > + ccwIplRead->chain = 0; /* Chain flag */ > + ccwIplRead->count = 0x18; /* Read 0x18 bytes of data */ > +} > + > +static void run_readipl(SubChannelId schid, uint16_t cutype) > +{ > + if (do_cio(schid, cutype, 0x00, CCW_FMT0)) { > + panic("dasd-ipl: Failed to run Read IPL channel program\n"); > + } > +} > + > +/* > + * The architecture states that IPL1 data should consist of a psw followed by > + * format-0 READ and TIC CCWs. Let's sanity check. > + */ > +static void check_ipl1(void) > +{ > + Ccw0 *ccwread = (Ccw0 *)0x08; > + Ccw0 *ccwtic = (Ccw0 *)0x10; > + > + if (ccwread->cmd_code != CCW_CMD_DASD_READ || > + ccwtic->cmd_code != CCW_CMD_TIC) { > + panic("dasd-ipl: IPL1 data invalid. Is this disk really bootable?\n"); > + } > +} > + > +static void check_ipl2(uint32_t ipl2_addr) > +{ > + Ccw0 *ccw = u32toptr(ipl2_addr); > + > + if (ipl2_addr == 0x00) { > + panic("IPL2 address invalid. Is this disk really bootable?\n"); > + } > + if (ccw->cmd_code == 0x00) { > + panic("IPL2 ccw data invalid. Is this disk really bootable?\n"); > + } > +} > + > +static uint32_t read_ipl2_addr(void) > +{ > + Ccw0 *ccwtic = (Ccw0 *)0x10; > + > + return ccwtic->cda; > +} > + > +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); lowcore->ccw1 ? > + /* 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); > + 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); > + 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, uint16_t cutype) > + { > + uint32_t startAddr = 0x08; > + > + if (do_cio(schid, cutype, startAddr, CCW_FMT0)) { > + panic("dasd-ipl: Failed to run IPL1 channel program\n"); > + } > +} > + > +static void run_ipl2(SubChannelId schid, uint16_t cutype, uint32_t addr) > +{ > + if (run_dynamic_ccw_program(schid, cutype, addr)) { > + panic("dasd-ipl: Failed to run IPL2 channel program\n"); > + } > +} > + > +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"); > +} Have you tried to use jump_to_low_kernel() already? ... it might be cleaner to do the diag 0x308 reset here, too, to avoid that some part of the machine is in an unexpected state... Thomas
On 3/29/19 4:33 AM, Thomas Huth wrote: > On 13/03/2019 17.31, Jason J. Herne wrote: > > s/tansfers/transfers/ > Will fix this, and the other typos you've pointed out. ... >> +static char prefix_page[PAGE_SIZE * 2] >> + __attribute__((__aligned__(PAGE_SIZE * 2))); >> + >> +static void enable_prefixing(void) >> +{ >> + memcpy(&prefix_page, (void *)0, 4096); > > You could use the "lowcore" variable from s390-arch.h here instead of > "(void *)0", I guess. > Agreed. >> + set_prefix(ptr2u32(&prefix_page)); >> +} >> + >> +static void disable_prefixing(void) >> +{ >> + set_prefix(0); >> + /* Copy io interrupt info back to low core */ >> + memcpy((void *)0xB8, prefix_page + 0xB8, 12); > > Maybe use &lowcore->subchannel_id instead of 0xB8 ? ... not sure whether > that's nicer here, though... > I think it is nicer using the named field. I Will make that change. Note: We need to keep the (void*) cast to prevent a compiler warning about discarding const qualifier. >> +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); > > lowcore->ccw1 ? > All the other CCWs in this section still need to use the numeric memory references. I think it makes it slightly more confusing to switch just the one to using the struct. For this reason I prefer it the way it is, if you're okay with that. ... >> +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"); >> +} > > Have you tried to use jump_to_low_kernel() already? ... it might be > cleaner to do the diag 0x308 reset here, too, to avoid that some part of > the machine is in an unexpected state... > > Thomas I had not tried jump_to_low_kernel() until just now. It *does* seem to work... and eliminates the need for the manual register clearing. I assume the diag 308 reset baked into the jump_to_low_kernel() is responsible for that? I guess switching to jump_to_low_kernel() would be a good thing ... I'll admit I'm slightly uneasy about it since I've been testing my way for so long :) But jump_to_low_kernel() works for all of my manual test cases.
On 01/04/2019 17.35, Jason J. Herne wrote: > On 3/29/19 4:33 AM, Thomas Huth wrote: >> On 13/03/2019 17.31, Jason J. Herne wrote: [...] >>> +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); >> >> lowcore->ccw1 ? >> > > All the other CCWs in this section still need to use the numeric memory > references. I think it makes it slightly more confusing to switch just > the one to using the struct. For this reason I prefer it the way it is, > if you're okay with that. Fine for me. > ... >>> +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"); >>> +} >> >> Have you tried to use jump_to_low_kernel() already? ... it might be >> cleaner to do the diag 0x308 reset here, too, to avoid that some part of >> the machine is in an unexpected state... > > I had not tried jump_to_low_kernel() until just now. It *does* seem to > work... and eliminates the need for the manual register clearing. I > assume the diag 308 reset baked into the jump_to_low_kernel() is > responsible for that? I guess switching to jump_to_low_kernel() would be > a good thing ... I'll admit I'm slightly uneasy about it since I've been > testing my way for so long :) But jump_to_low_kernel() works for all of > my manual test cases. I originally used lpsw in the netboot code, too, but there was the risk that some device activity in the background could confuse the OS kernel later ... so Christian pointed me to the diag diag 308 reset code, which is certainly the better way to hand over the control to the OS. Thus if it passes your test cases, I'd say let's try to do it the better way here right from the start and switch to jump_to_low_kernel() instead. Thomas
diff --git a/MAINTAINERS b/MAINTAINERS index 4801a48..03152b1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1166,6 +1166,7 @@ S: Supported F: hw/s390x/ipl.* F: pc-bios/s390-ccw/ F: pc-bios/s390-ccw.img +F: docs/devel/s390-dasd-ipl.txt T: git https://github.com/borntraeger/qemu.git s390-next L: qemu-s390x@nongnu.org diff --git a/docs/devel/s390-dasd-ipl.txt b/docs/devel/s390-dasd-ipl.txt new file mode 100644 index 0000000..236428a --- /dev/null +++ b/docs/devel/s390-dasd-ipl.txt @@ -0,0 +1,133 @@ +***************************** +***** s390 hardware IPL ***** +***************************** + +The s390 hardware IPL process consists of the following steps. + +1. A READ IPL ccw is constructed in memory location 0x0. + This ccw, by definition, reads the IPL1 record which is located on the disk + at cylinder 0 track 0 record 1. Note that the chain flag is on in this ccw + so when it is complete another ccw will be fetched and executed from memory + location 0x08. + +2. Execute the Read IPL ccw at 0x00, thereby reading IPL1 data into 0x00. + IPL1 data is 24 bytes in length and consists of the following pieces of + information: [psw][read ccw][tic ccw]. When the machine executes the Read + IPL ccw it read the 24-bytes of IPL1 to be read into memory starting at + location 0x0. Then the ccw program at 0x08 which consists of a read + ccw and a tic ccw is automatically executed because of the chain flag from + the original READ IPL ccw. The read ccw will read the IPL2 data into memory + and the TIC (Tranfer In Channel) will transfer control to the channel + program contained in the IPL2 data. The TIC channel command is the + equivalent of a branch/jump/goto instruction for channel programs. + NOTE: The ccws in IPL1 are defined by the architecture to be format 0. + +3. Execute IPL2. + The TIC ccw instruction at the end of the IPL1 channel program will begin + the execution of the IPL2 channel program. IPL2 is stage-2 of the boot + process and will contain a larger channel program than IPL1. The point of + IPL2 is to find and load either the operating system or a small program that + loads the operating system from disk. At the end of this step all or some of + the real operating system is loaded into memory and we are ready to hand + control over to the guest operating system. At this point the guest + operating system is entirely responsible for loading any more data it might + need to function. NOTE: The IPL2 channel program might read data into memory + location 0 thereby overwriting the IPL1 psw and channel program. This is ok + as long as the data placed in location 0 contains a psw whose instruction + address points to the guest operating system code to execute at the end of + the IPL/boot process. + NOTE: The ccws in IPL2 are defined by the architecture to be format 0. + +4. Start executing the guest operating system. + The psw that was loaded into memory location 0 as part of the ipl process + should contain the needed flags for the operating system we have loaded. The + psw's instruction address will point to the location in memory where we want + to start executing the operating system. This psw is loaded (via LPSW + instruction) causing control to be passed to the operating system code. + +In a non-virtualized environment this process, handled entirely by the hardware, +is kicked off by the user initiating a "Load" procedure from the hardware +management console. This "Load" procedure crafts a special "Read IPL" ccw in +memory location 0x0 that reads IPL1. It then executes this ccw thereby kicking +off the reading of IPL1 data. Since the channel program from IPL1 will be +written immediately after the special "Read IPL" ccw, the IPL1 channel program +will be executed immediately (the special read ccw has the chaining bit turned +on). The TIC at the end of the IPL1 channel program will cause the IPL2 channel +program to be executed automatically. After this sequence completes the "Load" +procedure then loads the psw from 0x0. + +********************************************************** +***** How this all pertains to QEMU (and the kernel) ***** +********************************************************** + +In theory we should merely have to do the following to IPL/boot a guest +operating system from a DASD device: + +1. Place a "Read IPL" ccw into memory location 0x0 with chaining bit on. +2. Execute channel program at 0x0. +3. LPSW 0x0. + +However, our emulation of the machine's channel program logic within the kernel +is missing one key feature that is required for this process to work: +non-prefetch of ccw data. + +When we start a channel program we pass the channel subsystem parameters via an +ORB (Operation Request Block). One of those parameters is a prefetch bit. If the +bit is on then the vfio-ccw kernel driver is allowed to read the entire channel +program from guest memory before it starts executing it. This means that any +channel commands that read additional channel commands will not work as expected +because the newly read commands will only exist in guest memory and NOT within +the kernel's channel subsystem memory. The kernel vfio-ccw driver currently +requires this bit to be on for all channel programs. This is a problem because +the IPL process consists of transferring control from the "Read IPL" ccw +immediately to the IPL1 channel program that was read by "Read IPL". + +Not being able to turn off prefetch will also prevent the TIC at the end of the +IPL1 channel program from transferring control to the IPL2 channel program. + +Lastly, in some cases (the zipl bootloader for example) the IPL2 program also +tansfers control to another channel program segment immediately after reading it +from the disk. So we need to be able to handle this case. + +************************** +***** What QEMU does ***** +************************** + +Since we are forced to live with prefetch we cannot use the very simple IPL +procedure we defined in the preceding section. So we compensate by doing the +following. + +1. Place "Read IPL" ccw into memory location 0x0, but turn off chaining bit. +2. Execute "Read IPL" at 0x0. + + So now IPL1's psw is at 0x0 and IPL1's channel program is at 0x08. + +4. Write a custom channel program that will seek to the IPL2 record and then + execute the READ and TIC ccws from IPL1. Normamly the seek is not required + because after reading the IPL1 record the disk is automatically positioned + to read the very next record which will be IPL2. But since we are not reading + both IPL1 and IPL2 as part of the same channel program we must manually set + the position. + +5. Grab the target address of the TIC instruction from the IPL1 channel program. + This address is where the IPL2 channel program starts. + + Now IPL2 is loaded into memory somewhere, and we know the address. + +6. Execute the IPL2 channel program at the address obtained in step #5. + + Because this channel program can be dynamic, we must use a special algorithm + that detects a READ immediately followed by a TIC and breaks the ccw chain + by turning off the chain bit in the READ ccw. When control is returned from + the kernel/hardware to the QEMU bios code we immediately issue another start + subchannel to execute the remaining TIC instruction. This causes the entire + channel program (starting from the TIC) and all needed data to be refetched + thereby stepping around the limitation that would otherwise prevent this + channel program from executing properly. + + Now the operating system code is loaded somewhere in guest memory and the psw + in memory location 0x0 will point to entry code for the guest operating + system. + +7. LPSW 0x0. + LPSW transfers control to the guest operating system and we're done. diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile index 12ad9c1..a048b6b 100644 --- a/pc-bios/s390-ccw/Makefile +++ b/pc-bios/s390-ccw/Makefile @@ -10,7 +10,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw) .PHONY : all clean build-all OBJECTS = start.o main.o bootmap.o jump2ipl.o sclp.o menu.o \ - virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o + virtio.o virtio-scsi.o virtio-blkdev.o libc.o cio.o dasd-ipl.o QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS)) QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float diff --git a/pc-bios/s390-ccw/dasd-ipl.c b/pc-bios/s390-ccw/dasd-ipl.c new file mode 100644 index 0000000..1a44469 --- /dev/null +++ b/pc-bios/s390-ccw/dasd-ipl.c @@ -0,0 +1,249 @@ +/* + * S390 IPL (boot) from a real DASD device via vfio framework. + * + * Copyright (c) 2019 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. + */ + +#include "libc.h" +#include "s390-ccw.h" +#include "s390-arch.h" +#include "dasd-ipl.h" +#include "helper.h" + +static char prefix_page[PAGE_SIZE * 2] + __attribute__((__aligned__(PAGE_SIZE * 2))); + +static void enable_prefixing(void) +{ + memcpy(&prefix_page, (void *)0, 4096); + set_prefix(ptr2u32(&prefix_page)); +} + +static void disable_prefixing(void) +{ + set_prefix(0); + /* Copy io interrupt info back to low core */ + memcpy((void *)0xB8, prefix_page + 0xB8, 12); +} + +static bool is_read_tic_ccw_chain(Ccw0 *ccw) +{ + Ccw0 *next_ccw = ccw + 1; + + return ((ccw->cmd_code == CCW_CMD_DASD_READ || + ccw->cmd_code == CCW_CMD_DASD_READ_MT) && + ccw->chain && next_ccw->cmd_code == CCW_CMD_TIC); +} + +static bool dynamic_cp_fixup(uint32_t ccw_addr, uint32_t *next_cpa) +{ + Ccw0 *cur_ccw = (Ccw0 *)(uint64_t)ccw_addr; + Ccw0 *tic_ccw; + + while (true) { + /* Skip over inline TIC (it might not have the chain bit on) */ + if (cur_ccw->cmd_code == CCW_CMD_TIC && + cur_ccw->cda == ptr2u32(cur_ccw) - 8) { + cur_ccw += 1; + continue; + } + + if (!cur_ccw->chain) { + break; + } + if (is_read_tic_ccw_chain(cur_ccw)) { + /* + * Breaking a chain of CCWs may alter the semantics or even the + * validity of a channel program. The heuristic implemented below + * seems to work well in practice for the channel programs + * generated by zipl. + */ + tic_ccw = cur_ccw + 1; + *next_cpa = tic_ccw->cda; + cur_ccw->chain = 0; + return true; + } + cur_ccw += 1; + } + return false; +} + +static int run_dynamic_ccw_program(SubChannelId schid, uint16_t cutype, + uint32_t cpa) +{ + bool has_next; + uint32_t next_cpa = 0; + int rc; + + do { + has_next = dynamic_cp_fixup(cpa, &next_cpa); + + print_int("executing ccw chain at ", cpa); + enable_prefixing(); + rc = do_cio(schid, cutype, cpa, CCW_FMT0); + disable_prefixing(); + + if (rc) { + break; + } + cpa = next_cpa; + } while (has_next); + + return rc; +} + +static void make_readipl(void) +{ + Ccw0 *ccwIplRead = (Ccw0 *)0x00; + + /* Create Read IPL ccw at address 0 */ + ccwIplRead->cmd_code = CCW_CMD_READ_IPL; + ccwIplRead->cda = 0x00; /* Read into address 0x00 in main memory */ + ccwIplRead->chain = 0; /* Chain flag */ + ccwIplRead->count = 0x18; /* Read 0x18 bytes of data */ +} + +static void run_readipl(SubChannelId schid, uint16_t cutype) +{ + if (do_cio(schid, cutype, 0x00, CCW_FMT0)) { + panic("dasd-ipl: Failed to run Read IPL channel program\n"); + } +} + +/* + * The architecture states that IPL1 data should consist of a psw followed by + * format-0 READ and TIC CCWs. Let's sanity check. + */ +static void check_ipl1(void) +{ + Ccw0 *ccwread = (Ccw0 *)0x08; + Ccw0 *ccwtic = (Ccw0 *)0x10; + + if (ccwread->cmd_code != CCW_CMD_DASD_READ || + ccwtic->cmd_code != CCW_CMD_TIC) { + panic("dasd-ipl: IPL1 data invalid. Is this disk really bootable?\n"); + } +} + +static void check_ipl2(uint32_t ipl2_addr) +{ + Ccw0 *ccw = u32toptr(ipl2_addr); + + if (ipl2_addr == 0x00) { + panic("IPL2 address invalid. Is this disk really bootable?\n"); + } + if (ccw->cmd_code == 0x00) { + panic("IPL2 ccw data invalid. Is this disk really bootable?\n"); + } +} + +static uint32_t read_ipl2_addr(void) +{ + Ccw0 *ccwtic = (Ccw0 *)0x10; + + return ccwtic->cda; +} + +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); + 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); + 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, uint16_t cutype) + { + uint32_t startAddr = 0x08; + + if (do_cio(schid, cutype, startAddr, CCW_FMT0)) { + panic("dasd-ipl: Failed to run IPL1 channel program\n"); + } +} + +static void run_ipl2(SubChannelId schid, uint16_t cutype, uint32_t addr) +{ + if (run_dynamic_ccw_program(schid, cutype, addr)) { + panic("dasd-ipl: Failed to run IPL2 channel program\n"); + } +} + +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 vfio-ccw support complicate the IPL process. Details can + * be found in docs/devel/s390-dasd-ipl.txt + */ +void dasd_ipl(SubChannelId schid, uint16_t cutype) +{ + uint32_t ipl2_addr; + + /* Construct Read IPL CCW and run it to read IPL1 from boot disk */ + make_readipl(); + run_readipl(schid, cutype); + ipl2_addr = read_ipl2_addr(); + check_ipl1(); + + /* + * Fixup IPL1 channel program to account for vfio-ccw limitations, then run + * it to read IPL2 channel program from boot disk. + */ + ipl1_fixup(); + run_ipl1(schid, cutype); + 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, cutype, 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..c394828 --- /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) 2019 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, uint16_t cutype); + +#endif /* DASD_IPL_H */ diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c index 57a1013..3c449ad 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 }; @@ -209,6 +210,10 @@ int main(void) cutype = cu_type(blk_schid); switch (cutype) { + case CU_TYPE_DASD_3990: + case CU_TYPE_DASD_2107: + dasd_ipl(blk_schid, cutype); /* 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 5e92c7a..504fc7c 100644 --- a/pc-bios/s390-ccw/s390-arch.h +++ b/pc-bios/s390-ccw/s390-arch.h @@ -87,4 +87,17 @@ typedef struct LowCore { extern LowCore const *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