Commit 102d8325 authored by Ingo Molnar's avatar Ingo Molnar Committed by Avi Kivity

KVM: add MSR based hypercall API

This adds a special MSR based hypercall API to KVM. This is to be
used by paravirtual kernels and virtual drivers.
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 5972e953
......@@ -14,6 +14,7 @@
#include "vmx.h"
#include <linux/kvm.h>
#include <linux/kvm_para.h>
#define CR0_PE_MASK (1ULL << 0)
#define CR0_TS_MASK (1ULL << 3)
......@@ -237,6 +238,9 @@ struct kvm_vcpu {
unsigned long cr0;
unsigned long cr2;
unsigned long cr3;
gpa_t para_state_gpa;
struct page *para_state_page;
gpa_t hypercall_gpa;
unsigned long cr4;
unsigned long cr8;
u64 pdptrs[4]; /* pae */
......@@ -382,6 +386,8 @@ struct kvm_arch_ops {
int (*run)(struct kvm_vcpu *vcpu, struct kvm_run *run);
int (*vcpu_setup)(struct kvm_vcpu *vcpu);
void (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);
void (*patch_hypercall)(struct kvm_vcpu *vcpu,
unsigned char *hypercall_addr);
};
extern struct kvm_stat kvm_stat;
......
......@@ -1204,6 +1204,73 @@ void realmode_set_cr(struct kvm_vcpu *vcpu, int cr, unsigned long val,
}
}
/*
* Register the para guest with the host:
*/
static int vcpu_register_para(struct kvm_vcpu *vcpu, gpa_t para_state_gpa)
{
struct kvm_vcpu_para_state *para_state;
hpa_t para_state_hpa, hypercall_hpa;
struct page *para_state_page;
unsigned char *hypercall;
gpa_t hypercall_gpa;
printk(KERN_DEBUG "kvm: guest trying to enter paravirtual mode\n");
printk(KERN_DEBUG ".... para_state_gpa: %08Lx\n", para_state_gpa);
/*
* Needs to be page aligned:
*/
if (para_state_gpa != PAGE_ALIGN(para_state_gpa))
goto err_gp;
para_state_hpa = gpa_to_hpa(vcpu, para_state_gpa);
printk(KERN_DEBUG ".... para_state_hpa: %08Lx\n", para_state_hpa);
if (is_error_hpa(para_state_hpa))
goto err_gp;
para_state_page = pfn_to_page(para_state_hpa >> PAGE_SHIFT);
para_state = kmap_atomic(para_state_page, KM_USER0);
printk(KERN_DEBUG ".... guest version: %d\n", para_state->guest_version);
printk(KERN_DEBUG ".... size: %d\n", para_state->size);
para_state->host_version = KVM_PARA_API_VERSION;
/*
* We cannot support guests that try to register themselves
* with a newer API version than the host supports:
*/
if (para_state->guest_version > KVM_PARA_API_VERSION) {
para_state->ret = -KVM_EINVAL;
goto err_kunmap_skip;
}
hypercall_gpa = para_state->hypercall_gpa;
hypercall_hpa = gpa_to_hpa(vcpu, hypercall_gpa);
printk(KERN_DEBUG ".... hypercall_hpa: %08Lx\n", hypercall_hpa);
if (is_error_hpa(hypercall_hpa)) {
para_state->ret = -KVM_EINVAL;
goto err_kunmap_skip;
}
printk(KERN_DEBUG "kvm: para guest successfully registered.\n");
vcpu->para_state_page = para_state_page;
vcpu->para_state_gpa = para_state_gpa;
vcpu->hypercall_gpa = hypercall_gpa;
hypercall = kmap_atomic(pfn_to_page(hypercall_hpa >> PAGE_SHIFT),
KM_USER1) + (hypercall_hpa & ~PAGE_MASK);
kvm_arch_ops->patch_hypercall(vcpu, hypercall);
kunmap_atomic(hypercall, KM_USER1);
para_state->ret = 0;
err_kunmap_skip:
kunmap_atomic(para_state, KM_USER0);
return 0;
err_gp:
return 1;
}
int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
{
u64 data;
......@@ -1312,6 +1379,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
case MSR_IA32_MISC_ENABLE:
vcpu->ia32_misc_enable_msr = data;
break;
/*
* This is the 'probe whether the host is KVM' logic:
*/
case MSR_KVM_API_MAGIC:
return vcpu_register_para(vcpu, data);
default:
printk(KERN_ERR "kvm: unhandled wrmsr: 0x%x\n", msr);
return 1;
......
......@@ -1669,6 +1669,18 @@ static int is_disabled(void)
return 0;
}
static void
svm_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
{
/*
* Patch in the VMMCALL instruction:
*/
hypercall[0] = 0x0f;
hypercall[1] = 0x01;
hypercall[2] = 0xd9;
hypercall[3] = 0xc3;
}
static struct kvm_arch_ops svm_arch_ops = {
.cpu_has_kvm_support = has_svm,
.disabled_by_bios = is_disabled,
......@@ -1717,6 +1729,7 @@ static struct kvm_arch_ops svm_arch_ops = {
.run = svm_vcpu_run,
.skip_emulated_instruction = skip_emulated_instruction,
.vcpu_setup = svm_vcpu_setup,
.patch_hypercall = svm_patch_hypercall,
};
static int __init svm_init(void)
......
......@@ -1469,6 +1469,18 @@ static int handle_io(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
return 0;
}
static void
vmx_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
{
/*
* Patch in the VMCALL instruction:
*/
hypercall[0] = 0x0f;
hypercall[1] = 0x01;
hypercall[2] = 0xc1;
hypercall[3] = 0xc3;
}
static int handle_cr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
u64 exit_qualification;
......@@ -2064,6 +2076,7 @@ static struct kvm_arch_ops vmx_arch_ops = {
.run = vmx_vcpu_run,
.skip_emulated_instruction = skip_emulated_instruction,
.vcpu_setup = vmx_vcpu_setup,
.patch_hypercall = vmx_patch_hypercall,
};
static int __init vmx_init(void)
......
#ifndef __LINUX_KVM_PARA_H
#define __LINUX_KVM_PARA_H
/*
* Guest OS interface for KVM paravirtualization
*
* Note: this interface is totally experimental, and is certain to change
* as we make progress.
*/
/*
* Per-VCPU descriptor area shared between guest and host. Writable to
* both guest and host. Registered with the host by the guest when
* a guest acknowledges paravirtual mode.
*
* NOTE: all addresses are guest-physical addresses (gpa), to make it
* easier for the hypervisor to map between the various addresses.
*/
struct kvm_vcpu_para_state {
/*
* API version information for compatibility. If there's any support
* mismatch (too old host trying to execute too new guest) then
* the host will deny entry into paravirtual mode. Any other
* combination (new host + old guest and new host + new guest)
* is supposed to work - new host versions will support all old
* guest API versions.
*/
u32 guest_version;
u32 host_version;
u32 size;
u32 ret;
/*
* The address of the vm exit instruction (VMCALL or VMMCALL),
* which the host will patch according to the CPU model the
* VM runs on:
*/
u64 hypercall_gpa;
} __attribute__ ((aligned(PAGE_SIZE)));
#define KVM_PARA_API_VERSION 1
/*
* This is used for an RDMSR's ECX parameter to probe for a KVM host.
* Hopefully no CPU vendor will use up this number. This is placed well
* out of way of the typical space occupied by CPU vendors' MSR indices,
* and we think (or at least hope) it wont be occupied in the future
* either.
*/
#define MSR_KVM_API_MAGIC 0x87655678
#define KVM_EINVAL 1
#endif
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