Xen PV-on-HVM guest support (v3)
Subsystems (4)
PATCH 1/1 Xen PV-on-HVM guest support (v3)
[Repost; the patch was garbled in my previous attempt.]
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.
v3: separate blob_{addr,size}_{32,64}; move xen_hvm_config to struct kvm_arch; remove unneeded ifdefs; return -EFAULT, -E2BIG, etc. from xen_hvm_config; use is_long_mode(); remove debug printks; document ioctl in api.txt
---
Documentation/kvm/api.txt +24 -0
@@ -593,6 +593,30 @@ struct kvm_irqchip { } chip; }; +4.27 KVM_XEN_HVM_CONFIG + +Capability: KVM_CAP_XEN_HVM +Architectures: x86 +Type: vm ioctl +Parameters: struct kvm_xen_hvm_config (in) +Returns: 0 on success, -1 on error + +Sets the MSR that the Xen HVM guest uses to initialize its hypercall +page, and provides the starting address and size of the hypercall +blobs in userspace. When the guest writes the MSR, kvm copies one +page of a blob (32- or 64-bit, depending on the vcpu mode) to guest +memory. + +struct kvm_xen_hvm_config { + __u32 msr; + __u32 pad1; + __u64 blob_addr_32; + __u64 blob_addr_64; + __u8 blob_size_32; + __u8 blob_size_64; + __u8 pad2[30]; +}; + 5. The kvm_run structure Application code obtains a pointer to the kvm_run structure by
arch/x86/include/asm/kvm.h +1 -0
@@ -19,6 +19,7 @@#define __KVM_HAVE_MSIX#define __KVM_HAVE_MCE#define __KVM_HAVE_PIT_STATE2 +#define __KVM_HAVE_XEN_HVM/* Architectural interrupt line count. */ #define KVM_NR_INTERRUPTS 256
arch/x86/include/asm/kvm_host.h +2 -0
@@ -410,6 +410,8 @@ struct kvm_arch{unsigned long irq_sources_bitmap;u64 vm_init_tsc; + +struct kvm_xen_hvm_config xen_hvm_config; };struct kvm_vm_stat {
arch/x86/kvm/x86.c +41 -0
59 lines not on this page · raw message
include/linux/kvm.h +16 -0
@@ -436,6 +436,9 @@ struct kvm_ioeventfd {#endif #define KVM_CAP_IOEVENTFD 36#define KVM_CAP_SET_IDENTITY_MAP_ADDR 37 +#ifdef __KVM_HAVE_XEN_HVM +#define KVM_CAP_XEN_HVM 38 +#endif #ifdef KVM_CAP_IRQ_ROUTING
@@ -488,6 +491,18 @@ struct kvm_x86_mce { };#endif +#ifdef KVM_CAP_XEN_HVM +struct kvm_xen_hvm_config { +__u32 msr; +__u32 pad1; +__u64 blob_addr_32; +__u64 blob_addr_64; +__u8 blob_size_32; +__u8 blob_size_64; +__u8 pad2[30 ]; +}; +#endif +#define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)struct kvm_irqfd {
@@ -546,6 +561,7 @@ struct kvm_irqfd {#define KVM_CREATE_PIT2 _IOW(KVMIO, 0x77, struct kvm_pit_config)#define KVM_SET_BOOT_CPU_ID _IO(KVMIO, 0x78)#define KVM_IOEVENTFD _IOW(KVMIO, 0x79, struct kvm_ioeventfd) +#define KVM_XEN_HVM_CONFIG _IOW(KVMIO, 0x7a, struct kvm_xen_hvm_config)/* * ioctls for vcpu fds
Marcelo Tosatti
AppliedQuoted 20 lines · Ed Swierk
[Repost; the patch was garbled in my previous attempt.]
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.
Quoted 6 lines
v3: separate blob_{addr,size}_{32,64}; move
xen_hvm_configto structkvm_arch; remove unneeded ifdefs; return-EFAULT,-E2BIG, etc. fromxen_hvm_config; useis_long_mode(); remove debug printks; document ioctl in api.txtSigned-off-by Ed Swierk <[email protected]>
Applied, thanks.