From ffde22ac53b6d6b1d7206f1172176a667eead778 Mon Sep 17 00:00:00 2001 From: Ed Swierk Date: Thu, 15 Oct 2009 15:21:43 -0700 Subject: [PATCH] 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 Signed-off-by: Jan Kiszka Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- Documentation/kvm/api.txt | 24 +++++++++++++++++ arch/x86/include/asm/kvm.h | 1 + arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/x86.c | 46 +++++++++++++++++++++++++++++++++ include/linux/kvm.h | 16 ++++++++++++ 5 files changed, 89 insertions(+) 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 { } 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 flags; + __u32 msr; + __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 diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h index f02e87a5206f..ef9b4b73cce4 100644 --- a/arch/x86/include/asm/kvm.h +++ b/arch/x86/include/asm/kvm.h @@ -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 diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 179a919f53a4..36f3b53f5c27 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -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 { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5d450cc6f841..bb842db3ee7c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -857,6 +857,38 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 data) return 0; } +static int xen_hvm_config(struct kvm_vcpu *vcpu, u64 data) +{ + struct kvm *kvm = vcpu->kvm; + int lm = is_long_mode(vcpu); + u8 *blob_addr = lm ? (u8 *)(long)kvm->arch.xen_hvm_config.blob_addr_64 + : (u8 *)(long)kvm->arch.xen_hvm_config.blob_addr_32; + u8 blob_size = lm ? kvm->arch.xen_hvm_config.blob_size_64 + : kvm->arch.xen_hvm_config.blob_size_32; + u32 page_num = data & ~PAGE_MASK; + u64 page_addr = data & PAGE_MASK; + u8 *page; + int r; + + r = -E2BIG; + if (page_num >= blob_size) + goto out; + r = -ENOMEM; + page = kzalloc(PAGE_SIZE, GFP_KERNEL); + if (!page) + goto out; + r = -EFAULT; + if (copy_from_user(page, blob_addr + (page_num * PAGE_SIZE), PAGE_SIZE)) + goto out_free; + if (kvm_write_guest(kvm, page_addr, page, PAGE_SIZE)) + goto out_free; + r = 0; +out_free: + kfree(page); +out: + return r; +} + int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) { switch (msr) { @@ -972,6 +1004,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) "0x%x data 0x%llx\n", msr, data); break; default: + if (msr && (msr == vcpu->kvm->arch.xen_hvm_config.msr)) + return xen_hvm_config(vcpu, data); if (!ignore_msrs) { pr_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n", msr, data); @@ -1246,6 +1280,7 @@ int kvm_dev_ioctl_check_extension(long ext) case KVM_CAP_PIT2: case KVM_CAP_PIT_STATE2: case KVM_CAP_SET_IDENTITY_MAP_ADDR: + case KVM_CAP_XEN_HVM: r = 1; break; case KVM_CAP_COALESCED_MMIO: @@ -2441,6 +2476,17 @@ long kvm_arch_vm_ioctl(struct file *filp, r = 0; break; } + case KVM_XEN_HVM_CONFIG: { + r = -EFAULT; + if (copy_from_user(&kvm->arch.xen_hvm_config, argp, + sizeof(struct kvm_xen_hvm_config))) + goto out; + r = -EINVAL; + if (kvm->arch.xen_hvm_config.flags) + goto out; + r = 0; + break; + } default: ; } diff --git a/include/linux/kvm.h b/include/linux/kvm.h index f8f8900fc5ec..b694c1d2f918 100644 --- a/include/linux/kvm.h +++ b/include/linux/kvm.h @@ -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 flags; + __u32 msr; + __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