On 05/11/2011 11:17 PM, [email protected] wrote:
> From: Sasha Levin <[email protected]>
>
> e820 is expected to leave a memory gap within the low 32
> bits of RAM space. From the documentation of e820_setup_gap():
> /*
> * Search for the biggest gap in the low 32 bits of the e820
> * memory space. We pass this space to PCI to assign MMIO resources
> * for hotplug or unconfigured devices in.
> * Hopefully the BIOS let enough space left.
> */
>
> Not leaving such gap causes errors and hangs during the boot
> process.
>
> This patch adds a memory gap between 0xe0000000 and 0x100000000
> when using more than 0xe0000000 bytes for guest RAM.
>
> This patch updates the e820 table, slot allocations
> used for KVM_SET_USER_MEMORY_REGION.
>
> Changes in V2:
> - Allocate RAM with the gap to avoid altering the translation code.
> - New patch description.
>
> Changes in V3:
> - Remove unnecessary casts.
>
> Changes in V4:
> - Rewrite kvm__init_ram().
> - Document the 64bit gap within the code.
>
> Signed-off-by: Sasha Levin <[email protected]>
> ---
> tools/kvm/bios.c | 27 ++++++++++++----
> tools/kvm/include/kvm/e820.h | 2 +-
> tools/kvm/include/kvm/kvm.h | 2 +
> tools/kvm/kvm.c | 66 +++++++++++++++++++++++++++++++++++++----
> 4 files changed, 82 insertions(+), 15 deletions(-)
>
> diff --git a/tools/kvm/bios.c b/tools/kvm/bios.c
> index 2199c0c..3cd9b24 100644
> --- a/tools/kvm/bios.c
> +++ b/tools/kvm/bios.c
> @@ -61,8 +61,6 @@ static void e820_setup(struct kvm *kvm)
> size = guest_flat_to_host(kvm, E820_MAP_SIZE);
> mem_map = guest_flat_to_host(kvm, E820_MAP_START);
>
> - *size = E820_MEM_AREAS;
> -
> mem_map[i++] = (struct e820_entry) {
> .addr = REAL_MODE_IVT_BEGIN,
> .size = EBDA_START - REAL_MODE_IVT_BEGIN,
> @@ -78,13 +76,28 @@ static void e820_setup(struct kvm *kvm)
> .size = MB_BIOS_END - MB_BIOS_BEGIN,
> .type = E820_MEM_RESERVED,
> };
> - mem_map[i++] = (struct e820_entry) {
> - .addr = BZ_KERNEL_START,
> - .size = kvm->ram_size - BZ_KERNEL_START,
> - .type = E820_MEM_USABLE,
> - };
> + if (kvm->ram_size < KVM_32BIT_GAP_START) {
> + mem_map[i++] = (struct e820_entry) {
> + .addr = BZ_KERNEL_START,
> + .size = kvm->ram_size - BZ_KERNEL_START,
> + .type = E820_MEM_USABLE,
> + };
> + } else {
> + mem_map[i++] = (struct e820_entry) {
> + .addr = BZ_KERNEL_START,
> + .size = KVM_32BIT_GAP_START - BZ_KERNEL_START,
> + .type = E820_MEM_USABLE,
> + };
> + mem_map[i++] = (struct e820_entry) {
> + .addr = 0x100000000ULL,
> + .size = kvm->ram_size - KVM_32BIT_GAP_START,
> + .type = E820_MEM_USABLE,
> + };
> + }
>
> BUILD_BUG_ON(i > E820_MEM_AREAS);
> +
> + *size = i;
> }
>
> /**
> diff --git a/tools/kvm/include/kvm/e820.h b/tools/kvm/include/kvm/e820.h
> index 252ae1f..e0f5f2a 100644
> --- a/tools/kvm/include/kvm/e820.h
> +++ b/tools/kvm/include/kvm/e820.h
> @@ -8,7 +8,7 @@
> #define E820_MEM_USABLE 1
> #define E820_MEM_RESERVED 2
>
> -#define E820_MEM_AREAS 4
> +#define E820_MEM_AREAS 5
>
> struct e820_entry {
> u64 addr; /* start of memory segment */
> diff --git a/tools/kvm/include/kvm/kvm.h b/tools/kvm/include/kvm/kvm.h
> index 3dab78d..5e2e64c 100644
> --- a/tools/kvm/include/kvm/kvm.h
> +++ b/tools/kvm/include/kvm/kvm.h
> @@ -8,6 +8,8 @@
> #include <time.h>
>
> #define KVM_NR_CPUS (255)
> +#define KVM_32BIT_GAP_SIZE (512 << 20)
> +#define KVM_32BIT_GAP_START ((1ULL << 32) - KVM_32BIT_GAP_SIZE)
>
> struct kvm {
> int sys_fd; /* For system ioctls(), i.e.
> /dev/kvm */
> diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
> index 65793f2..a3d3dd8 100644
> --- a/tools/kvm/kvm.c
> +++ b/tools/kvm/kvm.c
> @@ -153,23 +153,64 @@ static bool kvm__cpu_supports_vm(void)
> return regs.ecx & (1 << feature);
> }
>
> -void kvm__init_ram(struct kvm *self)
> +static void kvm_register_mem_slot(struct kvm *kvm, u32 slot, u64 guest_phys,
> u64 size, void *userspace_addr)
> {
> struct kvm_userspace_memory_region mem;
> int ret;
>
> mem = (struct kvm_userspace_memory_region) {
> - .slot = 0,
> - .guest_phys_addr = 0x0UL,
> - .memory_size = self->ram_size,
> - .userspace_addr = (unsigned long) self->ram_start,
> + .slot = slot,
> + .guest_phys_addr = guest_phys,
> + .memory_size = size,
> + .userspace_addr = (u64)userspace_addr,
I am seeing:
CC kvm.o
kvm.c: In function ‘kvm_register_mem_slot’:
kvm.c:165:22: error: cast from pointer to integer of different size
[-Werror=pointer-to-int-cast]
cc1: all warnings being treated as errors
make: *** [kvm.o] Error 1
with this patch on 32-bit box.
> };
>
> - ret = ioctl(self->vm_fd, KVM_SET_USER_MEMORY_REGION, &mem);
> + ret = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, &mem);
> if (ret < 0)
> die_perror("KVM_SET_USER_MEMORY_REGION ioctl");
> }
>
> +/*
> + * Allocating RAM size bigger than 4GB requires us to leave a gap
> + * in the RAM which is used for PCI MMIO, hotplug, and unconfigured
> + * devices (see documentation of e820_setup_gap() for details).
> + *
> + * If we're required to initialize RAM bigger than 4GB, we will create
> + * a gap between 0xe0000000 and 0x100000000 in the guest virtual mem space.
> + */
> +
> +void kvm__init_ram(struct kvm *self)
> +{
> + u64 phys_start, phys_size;
> + void *host_mem;
> +
> + if (self->ram_size < KVM_32BIT_GAP_START) {
> + /* Use a single block of RAM for 32bit RAM */
> +
> + phys_start = 0;
> + phys_size = self->ram_size;
> + host_mem = self->ram_start;
> +
> + kvm_register_mem_slot(self, 0, 0, self->ram_size,
> self->ram_start);
> + } else {
> + /* First RAM range from zero to the PCI gap: */
> +
> + phys_start = 0;
> + phys_size = KVM_32BIT_GAP_START;
> + host_mem = self->ram_start;
> +
> + kvm_register_mem_slot(self, 0, phys_start, phys_size, host_mem);
> +
> + /* Second RAM range from 4GB to the end of RAM: */
> +
> + phys_start = 0x100000000ULL;
> + phys_size = self->ram_size - phys_size;
> + host_mem = self->ram_start + phys_start;
> +
> + kvm_register_mem_slot(self, 1, phys_start, phys_size, host_mem);
> + }
> +}
> +
> int kvm__max_cpus(struct kvm *self)
> {
> int ret;
> @@ -225,7 +266,18 @@ struct kvm *kvm__init(const char *kvm_dev, unsigned long
> ram_size)
>
> self->ram_size = ram_size;
>
> - self->ram_start = mmap(NULL, ram_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
> + if (self->ram_size < KVM_32BIT_GAP_START) {
> + self->ram_start = mmap(NULL, ram_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
> + } else {
> + self->ram_start = mmap(NULL, ram_size + KVM_32BIT_GAP_SIZE,
> PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
> + if (self->ram_start != MAP_FAILED) {
> + /*
> + * We mprotect the gap (see kvm__init_ram() for
> details) PROT_NONE so that
> + * if we accidently write to it, we will know.
> + */
> + mprotect(self->ram_start + KVM_32BIT_GAP_START,
> KVM_32BIT_GAP_SIZE, PROT_NONE);
> + }
> + }
> if (self->ram_start == MAP_FAILED)
> die("out of memory");
>
--
Best Regards,
Asias He
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