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kvm: Allow to set shadow MMU size

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Introduce the KVM-specific machine option kvm_shadow_mem. It allows to
set a custom shadow MMU size for the virtual machine. This is useful for
stress testing e.g.

Only x86 supports this for now, but it is in principle a generic
concept for all targets with shadow MMUs.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Jan Kiszka 2012-01-25 18:14:15 +01:00 committed by Marcelo Tosatti
parent cf4dc461a4
commit 39d6960aab
3 changed files with 21 additions and 1 deletions
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4
qemu-config.c
View File

@ -535,6 +535,10 @@ static QemuOptsList qemu_machine_opts = {
.name = "kernel_irqchip",
.type = QEMU_OPT_BOOL,
.help = "use KVM in-kernel irqchip",
}, {
.name = "kvm_shadow_mem",
.type = QEMU_OPT_SIZE,
.help = "KVM shadow MMU size",
},
{ /* End of list */ }
},

5
qemu-options.hx
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@ -32,7 +32,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
" selects emulated machine (-machine ? for list)\n"
" property accel=accel1[:accel2[:...]] selects accelerator\n"
" supported accelerators are kvm, xen, tcg (default: tcg)\n"
" kernel_irqchip=on|off controls accelerated irqchip support\n",
" kernel_irqchip=on|off controls accelerated irqchip support\n"
" kvm_shadow_mem=size of KVM shadow MMU\n",
QEMU_ARCH_ALL)
STEXI
@item -machine [type=]@var{name}[,prop=@var{value}[,...]]
@ -47,6 +48,8 @@ than one accelerator specified, the next one is used if the previous one fails
to initialize.
@item kernel_irqchip=on|off
Enables in-kernel irqchip support for the chosen accelerator when available.
@item kvm_shadow_mem=size
Defines the size of the KVM shadow MMU.
@end table
ETEXI

13
target-i386/kvm.c
View File

@ -646,7 +646,9 @@ static int kvm_get_supported_msrs(KVMState *s)
int kvm_arch_init(KVMState *s)
{
QemuOptsList *list = qemu_find_opts("machine");
uint64_t identity_base = 0xfffbc000;
uint64_t shadow_mem;
int ret;
struct utsname utsname;
@ -693,6 +695,17 @@ int kvm_arch_init(KVMState *s)
}
qemu_register_reset(kvm_unpoison_all, NULL);
if (!QTAILQ_EMPTY(&list->head)) {
shadow_mem = qemu_opt_get_size(QTAILQ_FIRST(&list->head),
"kvm_shadow_mem", -1);
if (shadow_mem != -1) {
shadow_mem /= 4096;
ret = kvm_vm_ioctl(s, KVM_SET_NR_MMU_PAGES, shadow_mem);
if (ret < 0) {
return ret;
}
}
}
return 0;
}