Commit 39d6960a authored by Jan Kiszka's avatar Jan Kiszka Committed by Marcelo Tosatti
Browse files

kvm: Allow to set shadow MMU size 



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: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent cf4dc461

qemu-config.c

+4 −0
Original line number Diff line number Diff line
@@ -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 */ }

    },

qemu-options.hx

+4 −1
Original line number Diff line number Diff line
@@ -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

target-i386/kvm.c

+13 −0
Original line number Diff line number Diff line
@@ -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;

}