Re: [Qemu-devel] i386: pc: align gpa<->hpa on 1GB boundary (v4)

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 6 Nov 2013 19:31:19 -0200
Marcelo Tosatti <mtosatti@redhat.com> wrote:

> 
> v2: condition enablement of new mapping to new machine types (Paolo)
> v3: fix changelog
> v4: rebase
> 
> -----
> 
> 
> Align guest physical address and host physical address
> beyond guest 4GB on a 1GB boundary.
> 
> Otherwise 1GB TLBs cannot be cached for the range.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 12c436e..d29196d 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1156,7 +1156,7 @@ FWCfgState *pc_memory_init(MemoryRegion *system_memory,
>  {
>      int linux_boot, i;
>      MemoryRegion *ram, *option_rom_mr;
> -    MemoryRegion *ram_below_4g, *ram_above_4g;
> +    MemoryRegion *ram_below_4g, *ram_above_4g, *ram_above_4g_piecetwo;
>      FWCfgState *fw_cfg;
>  
>      linux_boot = (kernel_filename != NULL);
> @@ -1177,10 +1177,45 @@ FWCfgState *pc_memory_init(MemoryRegion *system_memory,
>      e820_add_entry(0, below_4g_mem_size, E820_RAM);
>      if (above_4g_mem_size > 0) {
>          ram_above_4g = g_malloc(sizeof(*ram_above_4g));
> -        memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> -                                 below_4g_mem_size, above_4g_mem_size);
> -        memory_region_add_subregion(system_memory, 0x100000000ULL,
> +        /*
> +         *
> +         * If 1GB hugepages are used to back guest RAM, map guest address
> +         * space in the range [ramsize,ramsize+holesize] to the ram block
> +         * range [holestart, 4GB]
> +         *
> +         *                      0      h     4G     [ramsize,ramsize+holesize]
> +         *
> +         * guest-addr-space     [      ]     [      ][xxx]
> +         *                                /----------/
> +         * contiguous-ram-block [      ][xxx][     ]
> +         *
> +         * So that memory beyond 4GB is aligned on a 1GB boundary,
> +         * at the host physical address space.
> +         *
> +         */
I did some corner cases testing and there is alias overlapping in case 
  -m 4096 -mem-path /var/lib/hugetlbfs/global/pagesize-1GB

  0000000100000000-000000011fffffff (prio 0, RW): alias ram-above-4g-piecetwo @pc.ram 00000000e0000000-00000000ffffffff
  0000000100000000-0000000100000000 (prio 0, RW): alias ram-above-4g @pc.ram 0000000100000000-0000000100000000

perhaps zero sized ram-above-4g shouldn't be created at all?

in addition ram-above-4g-piecetwo starts at half page offset 00000000e0000000 but guest sees it 4Gb offset,
wouldn't it cause the same issue patch tries to solve but only for ram-above-4g-piecetwo tail sync host/guest offsets
are not 1Gb aligned?

there is more misalignment with:
 -m 4097 -mem-path /var/lib/hugetlbfs/global/pagesize-1GB

  0000000100000000-00000001000fffff (prio 0, RW): alias ram-above-4g @pc.ram 0000000100000000-00000001000fffff
  0000000100100000-00000001200fffff (prio 0, RW): alias ram-above-4g-piecetwo @pc.ram 00000000e0000000-00000000ffffffff

where ram-above-4g-piecetwo is aligned with 1Gb+1Mb GPA offset, in addition to 500Mb offset of HPA.
which would cause the same issue as above prehaps?

> +        if (guest_info->gb_align) {
> +            unsigned long holesize = 0x100000000ULL - below_4g_mem_size;
> +
> +            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> +                                    0x100000000ULL,
> +                                    above_4g_mem_size - holesize);
> +            memory_region_add_subregion(system_memory, 0x100000000ULL,
>                                      ram_above_4g);
> +
> +            ram_above_4g_piecetwo = g_malloc(sizeof(*ram_above_4g_piecetwo));
> +            memory_region_init_alias(ram_above_4g_piecetwo, NULL,
> +                                     "ram-above-4g-piecetwo", ram,
> +                                     0x100000000ULL - holesize, holesize);
> +            memory_region_add_subregion(system_memory,
> +                                        0x100000000ULL +
> +                                        above_4g_mem_size - holesize,
> +                                        ram_above_4g_piecetwo);
> +        } else {
> +            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> +                                    below_4g_mem_size, above_4g_mem_size);
> +            memory_region_add_subregion(system_memory, 0x100000000ULL,
> +                                    ram_above_4g);
> +        }
>          e820_add_entry(0x100000000ULL, above_4g_mem_size, E820_RAM);
>      }
>  
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index 4fdb7b6..686736e 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -60,6 +60,7 @@ static const int ide_irq[MAX_IDE_BUS] = { 14, 15 };
>  static bool has_pvpanic;
>  static bool has_pci_info = true;
>  static bool has_acpi_build = true;
> +static bool gb_align = true;
>  
>  /* PC hardware initialisation */
>  static void pc_init1(QEMUMachineInitArgs *args,
> @@ -128,6 +129,7 @@ static void pc_init1(QEMUMachineInitArgs *args,
>  
>      guest_info->has_pci_info = has_pci_info;
>      guest_info->isapc_ram_fw = !pci_enabled;
> +    guest_info->gb_align = gb_align;
>  
>      /* allocate ram and load rom/bios */
>      if (!xen_enabled()) {
> @@ -240,8 +242,14 @@ static void pc_init_pci(QEMUMachineInitArgs *args)
>      pc_init1(args, 1, 1);
>  }
>  
> +static void pc_compat_1_7(QEMUMachineInitArgs *args)
> +{
> +    gb_align = false;
> +}
> +
>  static void pc_compat_1_6(QEMUMachineInitArgs *args)
>  {
> +    pc_compat_1_7(args);
>      has_pci_info = false;
>      rom_file_in_ram = false;
>      has_acpi_build = false;
> @@ -274,6 +282,12 @@ static void pc_compat_1_2(QEMUMachineInitArgs *args)
>      disable_kvm_pv_eoi();
>  }
>  
> +static void pc_init_pci_1_7(QEMUMachineInitArgs *args)
> +{
> +    pc_compat_1_7(args);
> +    pc_init_pci(args);
> +}
> +
>  static void pc_init_pci_1_6(QEMUMachineInitArgs *args)
>  {
>      pc_compat_1_6(args);
> @@ -346,13 +360,21 @@ static void pc_xen_hvm_init(QEMUMachineInitArgs *args)
>      .desc = "Standard PC (i440FX + PIIX, 1996)", \
>      .hot_add_cpu = pc_hot_add_cpu
>  
> +#define PC_I440FX_1_8_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS
> +static QEMUMachine pc_i440fx_machine_v1_8 = {
> +    PC_I440FX_1_8_MACHINE_OPTIONS,
> +    .name = "pc-i440fx-1.8",
> +    .alias = "pc",
> +    .init = pc_init_pci,
> +    .is_default = 1,
> +};
> +
>  #define PC_I440FX_1_7_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS
>  static QEMUMachine pc_i440fx_machine_v1_7 = {
>      PC_I440FX_1_7_MACHINE_OPTIONS,
>      .name = "pc-i440fx-1.7",
>      .alias = "pc",
> -    .init = pc_init_pci,
> -    .is_default = 1,
> +    .init = pc_init_pci_1_7,
>  };
>  
>  #define PC_I440FX_1_6_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS
> @@ -754,6 +776,7 @@ static QEMUMachine xenfv_machine = {
>  
>  static void pc_machine_init(void)
>  {
> +    qemu_register_machine(&pc_i440fx_machine_v1_8);
>      qemu_register_machine(&pc_i440fx_machine_v1_7);
>      qemu_register_machine(&pc_i440fx_machine_v1_6);
>      qemu_register_machine(&pc_i440fx_machine_v1_5);
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index 4c191d3..c2eb568 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -50,6 +50,7 @@
>  static bool has_pvpanic;
>  static bool has_pci_info = true;
>  static bool has_acpi_build = true;
> +static bool gb_align = true;
>  
>  /* PC hardware initialisation */
>  static void pc_q35_init(QEMUMachineInitArgs *args)
> @@ -113,6 +114,7 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
>      guest_info->has_pci_info = has_pci_info;
>      guest_info->isapc_ram_fw = false;
>      guest_info->has_acpi_build = has_acpi_build;
> +    guest_info->gb_align = gb_align;
>  
>      /* allocate ram and load rom/bios */
>      if (!xen_enabled()) {
> @@ -222,8 +224,14 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
>      }
>  }
>  
> +static void pc_compat_1_7(QEMUMachineInitArgs *args)
> +{
> +   gb_align = false;
> +}
> +
>  static void pc_compat_1_6(QEMUMachineInitArgs *args)
>  {
> +    pc_compat_1_7(args);
>      has_pci_info = false;
>      rom_file_in_ram = false;
>      has_acpi_build = false;
> @@ -243,6 +251,12 @@ static void pc_compat_1_4(QEMUMachineInitArgs *args)
>      x86_cpu_compat_set_features("Westmere", FEAT_1_ECX, 0, CPUID_EXT_PCLMULQDQ);
>  }
>  
> +static void pc_q35_init_1_7(QEMUMachineInitArgs *args)
> +{
> +    pc_compat_1_7(args);
> +    pc_q35_init(args);
> +}
> +
>  static void pc_q35_init_1_6(QEMUMachineInitArgs *args)
>  {
>      pc_compat_1_6(args);
> @@ -266,13 +280,22 @@ static void pc_q35_init_1_4(QEMUMachineInitArgs *args)
>      .desc = "Standard PC (Q35 + ICH9, 2009)", \
>      .hot_add_cpu = pc_hot_add_cpu
>  
> +#define PC_Q35_1_8_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS
> +
> +static QEMUMachine pc_q35_machine_v1_8 = {
> +    PC_Q35_1_8_MACHINE_OPTIONS,
> +    .name = "pc-q35-1.8",
> +    .alias = "q35",
> +    .init = pc_q35_init,
> +};
> +
>  #define PC_Q35_1_7_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS
>  
>  static QEMUMachine pc_q35_machine_v1_7 = {
>      PC_Q35_1_7_MACHINE_OPTIONS,
>      .name = "pc-q35-1.7",
>      .alias = "q35",
> -    .init = pc_q35_init,
> +    .init = pc_q35_init_1_7,
>  };
>  
>  #define PC_Q35_1_6_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS
> @@ -313,6 +336,7 @@ static QEMUMachine pc_q35_machine_v1_4 = {
>  
>  static void pc_q35_machine_init(void)
>  {
> +    qemu_register_machine(&pc_q35_machine_v1_8);
>      qemu_register_machine(&pc_q35_machine_v1_7);
>      qemu_register_machine(&pc_q35_machine_v1_6);
>      qemu_register_machine(&pc_q35_machine_v1_5);
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 03cc0ba..35a6885 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -41,6 +41,7 @@ struct PcGuestInfo {
>      uint64_t *node_cpu;
>      FWCfgState *fw_cfg;
>      bool has_acpi_build;
> +    bool gb_align;
>  };
>  
>  /* parallel.c */