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authorEd Swierk <eswierk@aristanetworks.com>2009-10-15 18:21:43 -0400
committerAvi Kivity <avi@redhat.com>2009-12-03 02:32:18 -0500
commitffde22ac53b6d6b1d7206f1172176a667eead778 (patch)
tree16ab77d364ba26928136e6d18463845941b6dd2c /Documentation/kvm
parent94c30d9ca6fd00a69e367b91b6e13572c41938c5 (diff)
KVM: Xen PV-on-HVM guest support
Support for Xen PV-on-HVM guests can be implemented almost entirely in userspace, except for handling one annoying MSR that maps a Xen hypercall blob into guest address space. A generic mechanism to delegate MSR writes to userspace seems overkill and risks encouraging similar MSR abuse in the future. Thus this patch adds special support for the Xen HVM MSR. I implemented a new ioctl, KVM_XEN_HVM_CONFIG, that lets userspace tell KVM which MSR the guest will write to, as well as the starting address and size of the hypercall blobs (one each for 32-bit and 64-bit) that userspace has loaded from files. When the guest writes to the MSR, KVM copies one page of the blob from userspace to the guest. I've tested this patch with a hacked-up version of Gerd's userspace code, booting a number of guests (CentOS 5.3 i386 and x86_64, and FreeBSD 8.0-RC1 amd64) and exercising PV network and block devices. [jan: fix i386 build warning] [avi: future proof abi with a flags field] Signed-off-by: Ed Swierk <eswierk@aristanetworks.com> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'Documentation/kvm')
-rw-r--r--Documentation/kvm/api.txt24
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index 5a4bc8cf6d04..3e8684e48506 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -593,6 +593,30 @@ struct kvm_irqchip {
593 } chip; 593 } chip;
594}; 594};
595 595
5964.27 KVM_XEN_HVM_CONFIG
597
598Capability: KVM_CAP_XEN_HVM
599Architectures: x86
600Type: vm ioctl
601Parameters: struct kvm_xen_hvm_config (in)
602Returns: 0 on success, -1 on error
603
604Sets the MSR that the Xen HVM guest uses to initialize its hypercall
605page, and provides the starting address and size of the hypercall
606blobs in userspace. When the guest writes the MSR, kvm copies one
607page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
608memory.
609
610struct kvm_xen_hvm_config {
611 __u32 flags;
612 __u32 msr;
613 __u64 blob_addr_32;
614 __u64 blob_addr_64;
615 __u8 blob_size_32;
616 __u8 blob_size_64;
617 __u8 pad2[30];
618};
619
5965. The kvm_run structure 6205. The kvm_run structure
597 621
598Application code obtains a pointer to the kvm_run structure by 622Application code obtains a pointer to the kvm_run structure by