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| author | David Woodhouse <dwmw@amazon.co.uk> | 2022-11-27 12:22:10 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-30 10:59:37 -0500 |
| commit | d8ba8ba4c801b794f47852a6f1821ea48f83b5d1 (patch) | |
| tree | cf8743dc182b1ca2b49a8c619e834b4748b2639e /include/uapi/linux/kvm.h | |
| parent | 5ec3289b31ab9bb209be59cee360aac4b03f320a (diff) | |
| download | lwn-d8ba8ba4c801b794f47852a6f1821ea48f83b5d1.tar.gz lwn-d8ba8ba4c801b794f47852a6f1821ea48f83b5d1.zip | |
KVM: x86/xen: Allow XEN_RUNSTATE_UPDATE flag behaviour to be configured
Closer inspection of the Xen code shows that we aren't supposed to be
using the XEN_RUNSTATE_UPDATE flag unconditionally. It should be
explicitly enabled by guests through the HYPERVISOR_vm_assist hypercall.
If we randomly set the top bit of ->state_entry_time for a guest that
hasn't asked for it and doesn't expect it, that could make the runtimes
fail to add up and confuse the guest. Without the flag it's perfectly
safe for a vCPU to read its own vcpu_runstate_info; just not for one
vCPU to read *another's*.
I briefly pondered adding a word for the whole set of VMASST_TYPE_*
flags but the only one we care about for HVM guests is this, so it
seemed a bit pointless.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20221127122210.248427-3-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include/uapi/linux/kvm.h')
| -rw-r--r-- | include/uapi/linux/kvm.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 88448397642c..64dfe9c07c87 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1271,6 +1271,7 @@ struct kvm_x86_mce { #define KVM_XEN_HVM_CONFIG_RUNSTATE (1 << 3) #define KVM_XEN_HVM_CONFIG_EVTCHN_2LEVEL (1 << 4) #define KVM_XEN_HVM_CONFIG_EVTCHN_SEND (1 << 5) +#define KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG (1 << 6) struct kvm_xen_hvm_config { __u32 flags; @@ -1776,6 +1777,7 @@ struct kvm_xen_hvm_attr { union { __u8 long_mode; __u8 vector; + __u8 runstate_update_flag; struct { __u64 gfn; } shared_info; @@ -1816,6 +1818,8 @@ struct kvm_xen_hvm_attr { /* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_EVTCHN_SEND */ #define KVM_XEN_ATTR_TYPE_EVTCHN 0x3 #define KVM_XEN_ATTR_TYPE_XEN_VERSION 0x4 +/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG */ +#define KVM_XEN_ATTR_TYPE_RUNSTATE_UPDATE_FLAG 0x5 /* Per-vCPU Xen attributes */ #define KVM_XEN_VCPU_GET_ATTR _IOWR(KVMIO, 0xca, struct kvm_xen_vcpu_attr) |