[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hy
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls |
Date: |
Thu, 20 Sep 2012 09:38:58 +0200 |
On 20.09.2012, at 09:08, David Gibson wrote:
> Currently the KVM exit path for PAPR hypercalls does not synchronize the
> qemu cpu state with the KVM state. Mostly this works, because the actual
> hypercall arguments and return values are explicitly passed through the
> kvm_run structure. However, the hypercall path includes a privilege check,
> to ensure that only the guest kernel can invoke hypercalls, not the guest
> userspace. Because of the lack of sync, this privilege check will use an
> out of date copy of the MSR, which could lead either to guest userspace
> being able to invoke hypercalls (a security hole for the guest) or to the
> guest kernel being incorrectly refused privilege leading to various other
> failures.
>
> This patch fixes the bug by forcing a synchronization on the hypercall exit
> path. This does mean we have a potentially quite expensive get and set of
> the state, however performance critical hypercalls are generally already
> implemented inside KVM so this probably won't matter. If it is a
> performance problem we can optimize it later by having the kernel perform
> the privilege check. That will need a new capability, however, since qemu
> will still need the privilege check for older kernels.
>
> Signed-off-by: David Gibson <address@hidden>
I would actually prefer to see that one fixed in kernel space. If we send it
through -stable there, we should be a lot better off. Also, PR KVM already
checks for !MSR_PR in kvm.
Alex
- [Qemu-ppc] [0/2] Bugfixes for ppc KVM, David Gibson, 2012/09/20
- [Qemu-ppc] [PATCH 2/2] target-ppc: KVM: Fix some kernel version edge cases for kvmppc_reset_htab(), David Gibson, 2012/09/20
- [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, David Gibson, 2012/09/20
- Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls,
Alexander Graf <=
- Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, David Gibson, 2012/09/20
- Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, Alexander Graf, 2012/09/20
- Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, David Gibson, 2012/09/20
- Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, Alexander Graf, 2012/09/24
- Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, David Gibson, 2012/09/25
Re: [Qemu-ppc] [PATCH 1/2] pseries: Synchronize qemu and KVM state on hypercalls, Jan Kiszka, 2012/09/20