Re: [Qemu-devel] [PATCH v5 10/12] hw/mips: malta: Add KVM support

[Aurelien Jarno <aurelien@aurel32.net>]

On Tue, Jun 17, 2014 at 11:10:35PM +0100, James Hogan wrote:
> In KVM mode the bootrom is loaded and executed from the last 1MB of
> DRAM.

What is the reason for that? I am not opposed to that, but if it is
really needed, it means that loading a bootloader into the flash area
(for example YAMON) won't work and that this should be forbidden to the
user.

> Based on "[PATCH 12/12] KVM/MIPS: General KVM support and support for
> SMP Guests" by Sanjay Lal <sanjayl@kymasys.com>.
> 
> Signed-off-by: James Hogan <james.hogan@imgtec.com>
> Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: Sanjay Lal <sanjayl@kymasys.com>
> ---
> Changes in v5:
>  - Kseg0 doesn't actually change size, so use cpu_mips_kseg0_to_phys()
>    rather than having the KVM specific cpu_mips_kvm_um_kseg0_to_phys().
> 
> Changes in v3:
>  - Remove unnecessary includes, especially linux/kvm.h which isn't a
>    good idea on non-Linux (Peter Maydell).
> 
> Changes in v2:
>  - Removal of cps / GIC / SMP support
>  - Minimal bootloader modified to execute safely from RAM
>  - Remove "Writing bootloader to final 1MB of RAM" printf
> ---
>  hw/mips/mips_malta.c | 73 ++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 53 insertions(+), 20 deletions(-)
> 
> diff --git a/hw/mips/mips_malta.c b/hw/mips/mips_malta.c
> index f4a7d4712952..8bc5392b4223 100644
> --- a/hw/mips/mips_malta.c
> +++ b/hw/mips/mips_malta.c
> @@ -51,6 +51,7 @@
>  #include "sysemu/qtest.h"
>  #include "qemu/error-report.h"
>  #include "hw/empty_slot.h"
> +#include "sysemu/kvm.h"
>  
>  //#define DEBUG_BOARD_INIT
>  
> @@ -603,29 +604,31 @@ static void network_init(PCIBus *pci_bus)
>  */
>  
>  static void write_bootloader (CPUMIPSState *env, uint8_t *base,
> -                              int64_t kernel_entry)
> +                              int64_t run_addr, int64_t kernel_entry)
>  {
>      uint32_t *p;
>  
>      /* Small bootloader */
>      p = (uint32_t *)base;
> -    stl_p(p++, 0x0bf00160);                                      /* j 0x1fc00580 */
> +
> +    stl_p(p++, 0x08000000 |                                      /* j 0x1fc00580 */
> +                 ((run_addr + 0x580) & 0x0fffffff) >> 2);
>      stl_p(p++, 0x00000000);                                      /* nop */
>  
>      /* YAMON service vector */
> -    stl_p(base + 0x500, 0xbfc00580);      /* start: */
> -    stl_p(base + 0x504, 0xbfc0083c);      /* print_count: */
> -    stl_p(base + 0x520, 0xbfc00580);      /* start: */
> -    stl_p(base + 0x52c, 0xbfc00800);      /* flush_cache: */
> -    stl_p(base + 0x534, 0xbfc00808);      /* print: */
> -    stl_p(base + 0x538, 0xbfc00800);      /* reg_cpu_isr: */
> -    stl_p(base + 0x53c, 0xbfc00800);      /* unred_cpu_isr: */
> -    stl_p(base + 0x540, 0xbfc00800);      /* reg_ic_isr: */
> -    stl_p(base + 0x544, 0xbfc00800);      /* unred_ic_isr: */
> -    stl_p(base + 0x548, 0xbfc00800);      /* reg_esr: */
> -    stl_p(base + 0x54c, 0xbfc00800);      /* unreg_esr: */
> -    stl_p(base + 0x550, 0xbfc00800);      /* getchar: */
> -    stl_p(base + 0x554, 0xbfc00800);      /* syscon_read: */
> +    stl_p(base + 0x500, run_addr + 0x0580);      /* start: */
> +    stl_p(base + 0x504, run_addr + 0x083c);      /* print_count: */
> +    stl_p(base + 0x520, run_addr + 0x0580);      /* start: */
> +    stl_p(base + 0x52c, run_addr + 0x0800);      /* flush_cache: */
> +    stl_p(base + 0x534, run_addr + 0x0808);      /* print: */
> +    stl_p(base + 0x538, run_addr + 0x0800);      /* reg_cpu_isr: */
> +    stl_p(base + 0x53c, run_addr + 0x0800);      /* unred_cpu_isr: */
> +    stl_p(base + 0x540, run_addr + 0x0800);      /* reg_ic_isr: */
> +    stl_p(base + 0x544, run_addr + 0x0800);      /* unred_ic_isr: */
> +    stl_p(base + 0x548, run_addr + 0x0800);      /* reg_esr: */
> +    stl_p(base + 0x54c, run_addr + 0x0800);      /* unreg_esr: */
> +    stl_p(base + 0x550, run_addr + 0x0800);      /* getchar: */
> +    stl_p(base + 0x554, run_addr + 0x0800);      /* syscon_read: */
>  
>  
>      /* Second part of the bootloader */
> @@ -701,7 +704,7 @@ static void write_bootloader (CPUMIPSState *env, uint8_t *base,
>      p = (uint32_t *) (base + 0x800);
>      stl_p(p++, 0x03e00008);                                     /* jr ra */
>      stl_p(p++, 0x24020000);                                     /* li v0,0 */
> -   /* 808 YAMON print */
> +    /* 808 YAMON print */
>      stl_p(p++, 0x03e06821);                                     /* move t5,ra */
>      stl_p(p++, 0x00805821);                                     /* move t3,a0 */
>      stl_p(p++, 0x00a05021);                                     /* move t2,a1 */
> @@ -774,6 +777,7 @@ static int64_t load_kernel (void)
>      uint32_t *prom_buf;
>      long prom_size;
>      int prom_index = 0;
> +    uint64_t (*xlate_to_kseg0) (void *opaque, uint64_t addr);
>  
>  #ifdef TARGET_WORDS_BIGENDIAN
>      big_endian = 1;
> @@ -788,6 +792,11 @@ static int64_t load_kernel (void)
>                  loaderparams.kernel_filename);
>          exit(1);
>      }
> +    if (kvm_enabled()) {
> +        xlate_to_kseg0 = cpu_mips_kvm_um_phys_to_kseg0;
> +    } else {
> +        xlate_to_kseg0 = cpu_mips_phys_to_kseg0;
> +    }
>  
>      /* load initrd */
>      initrd_size = 0;
> @@ -820,7 +829,7 @@ static int64_t load_kernel (void)
>      prom_set(prom_buf, prom_index++, "%s", loaderparams.kernel_filename);
>      if (initrd_size > 0) {
>          prom_set(prom_buf, prom_index++, "rd_start=0x%" PRIx64 " rd_size=%li %s",
> -                 cpu_mips_phys_to_kseg0(NULL, initrd_offset), initrd_size,
> +                 xlate_to_kseg0(NULL, initrd_offset), initrd_size,
>                   loaderparams.kernel_cmdline);
>      } else {
>          prom_set(prom_buf, prom_index++, "%s", loaderparams.kernel_cmdline);
> @@ -829,6 +838,7 @@ static int64_t load_kernel (void)
>      prom_set(prom_buf, prom_index++, "memsize");
>      prom_set(prom_buf, prom_index++, "%i",
>               MIN(loaderparams.ram_size, 256 << 20));
> +
>      prom_set(prom_buf, prom_index++, "modetty0");
>      prom_set(prom_buf, prom_index++, "38400n8r");
>      prom_set(prom_buf, prom_index++, NULL);
> @@ -863,6 +873,11 @@ static void main_cpu_reset(void *opaque)
>      }
>  
>      malta_mips_config(cpu);
> +
> +    if (kvm_enabled()) {
> +        /* Start running from the bootloader we wrote to end of RAM */
> +        env->active_tc.PC = 0x40000000 + loaderparams.ram_size;
> +    }
>  }
>  
>  static void cpu_request_exit(void *opaque, int irq, int level)
> @@ -878,6 +893,7 @@ static
>  void mips_malta_init(MachineState *machine)
>  {
>      ram_addr_t ram_size = machine->ram_size;
> +    ram_addr_t ram_low_size;
>      const char *cpu_model = machine->cpu_model;
>      const char *kernel_filename = machine->kernel_filename;
>      const char *kernel_cmdline = machine->kernel_cmdline;
> @@ -892,7 +908,7 @@ void mips_malta_init(MachineState *machine)
>      target_long bios_size = FLASH_SIZE;
>      const size_t smbus_eeprom_size = 8 * 256;
>      uint8_t *smbus_eeprom_buf = g_malloc0(smbus_eeprom_size);
> -    int64_t kernel_entry;
> +    int64_t kernel_entry, bootloader_run_addr;
>      PCIBus *pci_bus;
>      ISABus *isa_bus;
>      MIPSCPU *cpu;
> @@ -1011,13 +1027,30 @@ void mips_malta_init(MachineState *machine)
>      bios = pflash_cfi01_get_memory(fl);
>      fl_idx++;
>      if (kernel_filename) {
> +        ram_low_size = MIN(ram_size, 256 << 20);
> +        /* For KVM T&E we reserve 1MB of RAM for running bootloader */
> +        if (kvm_enabled()) {
> +            ram_low_size -= 0x100000;
> +            bootloader_run_addr = 0x40000000 + ram_low_size;
> +        } else {
> +            bootloader_run_addr = 0xbfc00000;
> +        }
> +
>          /* Write a small bootloader to the flash location. */
> -        loaderparams.ram_size = MIN(ram_size, 256 << 20);
> +        loaderparams.ram_size = ram_low_size;
>          loaderparams.kernel_filename = kernel_filename;
>          loaderparams.kernel_cmdline = kernel_cmdline;
>          loaderparams.initrd_filename = initrd_filename;
>          kernel_entry = load_kernel();
> -        write_bootloader(env, memory_region_get_ram_ptr(bios), kernel_entry);
> +
> +        write_bootloader(env, memory_region_get_ram_ptr(bios),
> +                         bootloader_run_addr, kernel_entry);
> +        if (kvm_enabled()) {
> +            /* Write the bootloader code @ the end of RAM, 1MB reserved */
> +            write_bootloader(env, memory_region_get_ram_ptr(ram_low_preio) +
> +                                    ram_low_size,
> +                             bootloader_run_addr, kernel_entry);
> +        }
>      } else {
>          /* Load firmware from flash. */
>          if (!dinfo) {
> -- 
> 1.9.3
> 
> 
> 

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net