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qemu-linux-user
0098-s390-bios-Support-booting-from-real.patch
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File 0098-s390-bios-Support-booting-from-real.patch of Package qemu-linux-user
From: "Jason J. Herne" <jjherne@linux.ibm.com> Date: Thu, 4 Apr 2019 10:34:34 -0400 Subject: s390-bios: Support booting from real dasd device 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> Message-Id: <1554388475-18329-16-git-send-email-jjherne@linux.ibm.com> Signed-off-by: Thomas Huth <thuth@redhat.com> (cherry picked from commit efa47d36da89f4b23c315a7cc085fab0d15eb47c) [LY: BSC#1145379 JIRA-SLE-6132] Signed-off-by: Liang Yan <lyan@suse.com> --- MAINTAINERS | 1 + docs/devel/s390-dasd-ipl.txt | 133 ++++++++++++++++++++ pc-bios/s390-ccw/Makefile | 2 +- pc-bios/s390-ccw/dasd-ipl.c | 235 +++++++++++++++++++++++++++++++++++ pc-bios/s390-ccw/dasd-ipl.h | 16 +++ pc-bios/s390-ccw/main.c | 5 + pc-bios/s390-ccw/s390-arch.h | 13 ++ 7 files changed, 404 insertions(+), 1 deletion(-) diff --git a/MAINTAINERS b/MAINTAINERS index 8dd0929d7c1765ae8b0ec98dd9e0..4715b2186781eedd179bf08afcc8 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1077,6 +1077,7 @@ 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 0000000000000000000000000000000000000000..9107e048e4e6a0695f02529ce325f3e2dd689e8a --- /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 (Transfer 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 +transfers 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. Normally 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 12ad9c1d5813d74a545cebf71537..a048b6b077a94a41f9fa41e3860b 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 0000000000000000000000000000000000000000..0fc879bb8e8faac7e56c41c37dcf330f09e4bbbc --- /dev/null +++ b/pc-bios/s390-ccw/dasd-ipl.c @@ -0,0 +1,235 @@ +/* + * 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, lowcore, 4096); + set_prefix(ptr2u32(&prefix_page)); +} + +static void disable_prefixing(void) +{ + set_prefix(0); + /* Copy io interrupt info back to low core */ + memcpy((void *)&lowcore->subchannel_id, 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"); + } +} + +/* + * 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) +{ + PSWLegacy *pswl = (PSWLegacy *) 0x00; + 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 + */ + run_ipl2(schid, cutype, ipl2_addr); + + /* Transfer control to the guest operating system */ + pswl->mask |= PSW_MASK_EAMODE; /* Force z-mode */ + pswl->addr |= PSW_MASK_BAMODE; /* ... */ + jump_to_low_kernel(); +} diff --git a/pc-bios/s390-ccw/dasd-ipl.h b/pc-bios/s390-ccw/dasd-ipl.h new file mode 100644 index 0000000000000000000000000000000000000000..c3948289062cd46da280a6e6a41dd9fa3c51790a --- /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 57a10138c65dd87b5f585912145b..3c449ad49688d7cd05b84076b0ae 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 5e92c7a27d53d6a0cfeee9510a41..504fc7c2f09878cb6b37e307bb20 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
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