Hi,
On Tue, Feb 22, 2022 at 02:18:40PM +0000, Marc Zyngier wrote:
> On 2022-02-22 13:58, Alexandru Elisei wrote:
> > Hi,
> >
> > On Tue, Feb 22, 2022 at 10:08:30AM +0000, Sebastian Ene wrote:
> > > This patch adds support for stolen time by sharing a memory region
> > > with the guest which will be used by the hypervisor to store the
> > > stolen
> > > time information. The exact format of the structure stored by the
> > > hypervisor is described in the ARM DEN0057A document.
> > >
> > > Signed-off-by: Sebastian Ene <sebastianene@xxxxxxxxxx>
> > > ---
> > > Changelog since v2:
> > > - Moved the AARCH64_PVTIME_* definitions from arm-common/kvm-arch.h
> > > to
> > > arm64/pvtime.c as pvtime is only available for arm64.
> > >
> > > Changelog since v1:
> > > - Removed the pvtime.h header file and moved the definitions to
> > > kvm-cpu-arch.h
> > > Verified if the stolen time capability is supported before
> > > allocating
> > > and mapping the memory.
> > >
> > > Makefile | 1 +
> > > arm/aarch64/arm-cpu.c | 1 +
> > > arm/aarch64/include/kvm/kvm-cpu-arch.h | 1 +
> > > arm/aarch64/pvtime.c | 89
> > > ++++++++++++++++++++++++++
> > > arm/kvm-cpu.c | 14 ++--
> > > 5 files changed, 99 insertions(+), 7 deletions(-)
> > > create mode 100644 arm/aarch64/pvtime.c
> > >
> > > diff --git a/Makefile b/Makefile
> > > index f251147..e9121dc 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -182,6 +182,7 @@ ifeq ($(ARCH), arm64)
> > > OBJS += arm/aarch64/arm-cpu.o
> > > OBJS += arm/aarch64/kvm-cpu.o
> > > OBJS += arm/aarch64/kvm.o
> > > + OBJS += arm/aarch64/pvtime.o
> > > ARCH_INCLUDE := $(HDRS_ARM_COMMON)
> > > ARCH_INCLUDE += -Iarm/aarch64/include
> > >
> > > diff --git a/arm/aarch64/arm-cpu.c b/arm/aarch64/arm-cpu.c
> > > index d7572b7..326fb20 100644
> > > --- a/arm/aarch64/arm-cpu.c
> > > +++ b/arm/aarch64/arm-cpu.c
> > > @@ -22,6 +22,7 @@ static void generate_fdt_nodes(void *fdt, struct
> > > kvm *kvm)
> > > static int arm_cpu__vcpu_init(struct kvm_cpu *vcpu)
> > > {
> > > vcpu->generate_fdt_nodes = generate_fdt_nodes;
> > > + kvm_cpu__setup_pvtime(vcpu);
> > > return 0;
> > > }
> > >
> > > diff --git a/arm/aarch64/include/kvm/kvm-cpu-arch.h
> > > b/arm/aarch64/include/kvm/kvm-cpu-arch.h
> > > index 8dfb82e..b57d6e6 100644
> > > --- a/arm/aarch64/include/kvm/kvm-cpu-arch.h
> > > +++ b/arm/aarch64/include/kvm/kvm-cpu-arch.h
> > > @@ -19,5 +19,6 @@
> > >
> > > void kvm_cpu__select_features(struct kvm *kvm, struct kvm_vcpu_init
> > > *init);
> > > int kvm_cpu__configure_features(struct kvm_cpu *vcpu);
> > > +void kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu);
> > >
> > > #endif /* KVM__KVM_CPU_ARCH_H */
> > > diff --git a/arm/aarch64/pvtime.c b/arm/aarch64/pvtime.c
> > > new file mode 100644
> > > index 0000000..247e4f3
> > > --- /dev/null
> > > +++ b/arm/aarch64/pvtime.c
> > > @@ -0,0 +1,89 @@
> > > +#include "kvm/kvm.h"
> > > +#include "kvm/kvm-cpu.h"
> > > +#include "kvm/util.h"
> > > +
> > > +#include <linux/byteorder.h>
> > > +#include <linux/types.h>
> > > +
> > > +#define AARCH64_PVTIME_IPA_MAX_SIZE SZ_64K
> > > +#define AARCH64_PVTIME_IPA_START (ARM_MEMORY_AREA - \
> > > + AARCH64_PVTIME_IPA_MAX_SIZE)
> >
> > This doesn't change the fact that it overlaps with KVM_PCI_MMIO_AREA,
> > which is
> > exposed to the guest in the DTB (see my reply to v2).
>
> Yup, this is a bit of a problem, and overlapping regions are
> a big no-no. Why can't the pvtime region be dynamically placed
> after the RAM (after checking that there is enough space to
> register it in the IPA space)?
In theory, is there something to stop someone from creating a VM with enough
memory to reach the end of the IPA space?
Thanks,
Alex
>
> Thanks,
>
> M.
> --
> Jazz is not dead. It just smells funny...
