This patch mmaps guest kernel into it's own memory slot instead of reading
it into the memory.
The advantages are:
- Smaller memory footprint (same effect as KSM if running multiple guests)
- Faster loading of larger kernels.
Suggested-by: "Sweeney, Andrew John" <ajsw...@sandia.gov>
Signed-off-by: Sasha Levin <levinsasha...@gmail.com>
---
tools/kvm/x86/include/kvm/kvm-arch.h | 4 ++
tools/kvm/x86/kvm.c | 60 +++++++++++++++++++++++++++-------
2 files changed, 52 insertions(+), 12 deletions(-)
diff --git a/tools/kvm/x86/include/kvm/kvm-arch.h
b/tools/kvm/x86/include/kvm/kvm-arch.h
index 686b1b8..3f7a311 100644
--- a/tools/kvm/x86/include/kvm/kvm-arch.h
+++ b/tools/kvm/x86/include/kvm/kvm-arch.h
@@ -35,6 +35,10 @@ struct kvm {
u64 ram_size;
void *ram_start;
+ int bz_fd;
+ void *bz_start;
+ u32 bz_len;
+
bool nmi_disabled;
bool single_step;
diff --git a/tools/kvm/x86/kvm.c b/tools/kvm/x86/kvm.c
index da4a6b6..42d7810 100644
--- a/tools/kvm/x86/kvm.c
+++ b/tools/kvm/x86/kvm.c
@@ -9,6 +9,7 @@
#include <asm/bootparam.h>
#include <linux/kvm.h>
+#include <linux/kernel.h>
#include <sys/types.h>
#include <sys/ioctl.h>
@@ -93,24 +94,51 @@ void kvm__init_ram(struct kvm *kvm)
void *host_mem;
if (kvm->ram_size < KVM_32BIT_GAP_START) {
- /* Use a single block of RAM for 32bit RAM */
-
+ /* Memory between 0 and where the kernel starts */
+ u64 bzl = ALIGN(kvm->bz_len, PAGE_SIZE);
phys_start = 0;
- phys_size = kvm->ram_size;
+ phys_size = BZ_KERNEL_START;
host_mem = kvm->ram_start;
kvm__register_mem(kvm, phys_start, phys_size, host_mem);
- } else {
- /* First RAM range from zero to the PCI gap: */
+ /* Mapped kernel */
+ phys_start = BZ_KERNEL_START;
+ phys_size = bzl;
+ host_mem = kvm->bz_start;
+
+ kvm__register_mem(kvm, phys_start, phys_size, host_mem);
+
+ /* Rest of the memory */
+ phys_start = BZ_KERNEL_START + bzl;
+ phys_size = kvm->ram_size - (BZ_KERNEL_START + bzl);
+ host_mem = kvm->ram_start + (BZ_KERNEL_START + bzl);
+
+ kvm__register_mem(kvm, phys_start, phys_size, host_mem);
+ } else {
+ /* Memory between 0 and where the kernel starts */
+ u64 bzl = ALIGN(kvm->bz_len, PAGE_SIZE);
phys_start = 0;
- phys_size = KVM_32BIT_GAP_START;
+ phys_size = BZ_KERNEL_START;
host_mem = kvm->ram_start;
kvm__register_mem(kvm, phys_start, phys_size, host_mem);
- /* Second RAM range from 4GB to the end of RAM: */
+ /* Mapped kernel */
+ phys_start = BZ_KERNEL_START;
+ phys_size = bzl;
+ host_mem = kvm->bz_start;
+ kvm__register_mem(kvm, phys_start, phys_size, host_mem);
+
+ /* Rest of the memory until the 4GB gap */
+ phys_start = BZ_KERNEL_START + bzl;
+ phys_size = KVM_32BIT_GAP_START - (BZ_KERNEL_START + bzl);
+ host_mem = kvm->ram_start + (BZ_KERNEL_START + bzl);
+
+ kvm__register_mem(kvm, phys_start, phys_size, host_mem);
+
+ /* RAM range from 4GB to the end of RAM */
phys_start = 0x100000000ULL;
phys_size = kvm->ram_size - phys_size;
host_mem = kvm->ram_start + phys_start;
@@ -232,7 +260,8 @@ bool load_bzimage(struct kvm *kvm, int fd_kernel,
struct boot_params *kern_boot;
unsigned long setup_sects;
struct boot_params boot;
- size_t cmdline_size;
+ struct stat st;
+ size_t cmdline_size, setup_end;
ssize_t setup_size;
void *p;
int nr;
@@ -242,6 +271,9 @@ bool load_bzimage(struct kvm *kvm, int fd_kernel,
* memory layout.
*/
+ if (fstat(fd_kernel, &st) < 0)
+ die_perror("fstat");
+
if (lseek(fd_kernel, 0, SEEK_SET) < 0)
die_perror("lseek");
@@ -268,11 +300,15 @@ bool load_bzimage(struct kvm *kvm, int fd_kernel,
if (read(fd_kernel, p, setup_size) != setup_size)
die_perror("read");
- /* copy vmlinux.bin to BZ_KERNEL_START*/
- p = guest_flat_to_host(kvm, BZ_KERNEL_START);
+ /* mmap the actual kernel */
+ kvm->bz_fd = dup(fd_kernel);
+ kvm->bz_len = st.st_size;
+ setup_end = ALIGN(setup_size - PAGE_SIZE, PAGE_SIZE); /* Need it
aligned to PAGE_SIZE */
+ kvm->bz_start = mmap(NULL, kvm->bz_len, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE, kvm->bz_fd, setup_end);
- while ((nr = read(fd_kernel, p, 65536)) > 0)
- p += nr;
+ /* NOP everything before the kernel start */
+ memset(kvm->bz_start, 0x90, setup_size - setup_end);
p = guest_flat_to_host(kvm, BOOT_CMDLINE_OFFSET);
if (kernel_cmdline) {
--
1.7.8
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