[PATCH 1/5] KVM paravirt_ops core infrastructure

Anthony Liguori
2007-06-18T02:58:11Z

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Regards,

Anthony Liguori

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Subject: [PATCH] KVM paravirt_ops core infrastructure
Author: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

This patch implements paravirt_ops support for KVM and updates the current
paravirtualization support in KVM to match. Some changes to the previous
paravirtualization support in KVM:

1) Theoritical support for SMP guests
2) Use CPUID to discover paravirtualization
3) Use feature bitmap instead of versioning

Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 8770a5d..97ad1e1 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -231,6 +231,13 @@ config VMI
at the moment), by linking the kernel to a GPL-ed ROM module
provided by the hypervisor.

+config KVM_GUEST
+ bool "KVM paravirt-ops support"
+ depends on PARAVIRT
+ help
+ This option enables various optimizations for running under the KVM
+ hypervisor.
+
config ACPI_SRAT
bool
default y
diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index 06da59f..12a4201 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_HPET_TIMER) += hpet.o
obj-$(CONFIG_K8_NB) += k8.o

obj-$(CONFIG_VMI) += vmi.o vmiclock.o
+obj-$(CONFIG_KVM_GUEST) += kvm.o
obj-$(CONFIG_PARAVIRT) += paravirt.o
obj-y += pcspeaker.o

diff --git a/arch/i386/kernel/kvm.c b/arch/i386/kernel/kvm.c
new file mode 100644
index 0000000..22ea647
--- /dev/null
+++ b/arch/i386/kernel/kvm.c
@@ -0,0 +1,219 @@
+/*
+ * KVM paravirt_ops implementation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Copyright (C) 2007, Red Hat, Inc., Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
+ * Copyright IBM Corporation, 2007
+ * Authors: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/kvm_para.h>
+#include <linux/cpu.h>
+#include <linux/mm.h>
+
+struct kvm_paravirt_state
+{
+ struct kvm_vmca *vmca;
+ struct kvm_hypercall_entry *queue;
+ void (*hypercall)(void);
+
+ u64 vmca_gpa;
+};
+
+static DEFINE_PER_CPU(struct kvm_paravirt_state *, paravirt_state);
+
+static int do_nop_io_delay;
+static u64 msr_set_vmca;
+
+static long kvm_hypercall(unsigned int nr, unsigned long p1,
+ unsigned long p2, unsigned long p3,
+ unsigned long p4)
+{
+ struct kvm_paravirt_state *state
+ = per_cpu(paravirt_state, smp_processor_id());
+ long ret;
+
+ asm volatile("call *(%6) \n\t"
+ : "=a"(ret)
+ : "a" (nr),
+ "b" (p1),
+ "c" (p2),
+ "d" (p3),
+ "S" (p4),
+ "r" (&state->hypercall)
+ : "memory", "cc"
+ );
+
+ return ret;
+}
+
+/*
+ * No need for any "IO delay" on KVM
+ */
+static void kvm_io_delay(void)
+{
+}
+
+static void paravirt_ops_setup(void)
+{
+ paravirt_ops.name = "KVM";
+
+ if (do_nop_io_delay)
+ paravirt_ops.io_delay = kvm_io_delay;
+
+ paravirt_ops.paravirt_enabled = 1;
+
+ apply_paravirt(__parainstructions, __parainstructions_end);
+}
+
+static void paravirt_activate(void *unused)
+{
+ struct kvm_paravirt_state *state
+ = per_cpu(paravirt_state, raw_smp_processor_id());
+ wrmsrl(msr_set_vmca, state->vmca_gpa);
+}
+
+static int paravirt_initialize(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+ char signature[13];
+
+ /* verify that we're running on KVM */
+ cpuid(CPUID_HYPE_IDENT, &eax, &ebx, &ecx, &edx);
+ memcpy(signature, &ebx, 4);
+ memcpy(signature + 4, &ecx, 4);
+ memcpy(signature + 8, &edx, 4);
+ signature[12] = 0;
+
+ if (strcmp(signature, "KVMKVMKVMKVM"))
+ return -EINVAL;
+
+ /* check what features are supported */
+ cpuid(CPUID_HYPE_KVM_FEATURES, &eax, &ebx, &ecx, &edx);
+ msr_set_vmca = eax;
+
+ /* no paravirtualization is supported */
+ if (!(edx & KVM_FEATURE_VMCA))
+ return -ENOSYS;
+
+ if ((edx & KVM_FEATURE_NOP_IO_DELAY))
+ do_nop_io_delay = 1;
+
+ on_each_cpu(paravirt_activate, NULL, 0, 1);
+
+ return 0;
+}
+
+static __init void paravirt_free_state(struct kvm_paravirt_state *state)
+{
+ if (!state)
+ return;
+
+ if (state->hypercall)
+ __free_page(pfn_to_page(__pa(state->hypercall) >> PAGE_SHIFT));
+
+ if (state->vmca)
+ __free_page(pfn_to_page(__pa(state->vmca) >> PAGE_SHIFT));
+
+ __free_page(pfn_to_page(__pa(state) >> PAGE_SHIFT));
+}
+
+static __init struct kvm_paravirt_state *paravirt_alloc_state(void)
+{
+ struct kvm_paravirt_state *state;
+
+ state = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!state)
+ goto err;
+
+ state->vmca = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!state->vmca)
+ goto err;
+
+ /* FIXME: what do I need for this to be executable on 64 bit? */
+ state->hypercall = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!state->hypercall)
+ goto err;
+
+ state->vmca_gpa = __pa(state->vmca);
+ state->vmca->hypercall_gpa = __pa(state->hypercall);
+
+ return state;
+
+ err:
+ paravirt_free_state(state);
+ return NULL;
+}
+
+/* FIXME: hotplug hooks whenever KVM supports CPU hotplug */
+
+static __init void paravirt_free_area(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ struct kvm_paravirt_state *state;
+ state = per_cpu(paravirt_state, cpu);
+ paravirt_free_state(state);
+ }
+}
+
+static __init int paravirt_alloc_area(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ struct kvm_paravirt_state *state;
+
+ state = paravirt_alloc_state();
+ if (!state)
+ goto err;
+
+ per_cpu(paravirt_state, cpu) = state;
+ }
+
+ return 0;
+
+ err:
+ paravirt_free_area();
+ return -ENOMEM;
+}
+
+static int __init kvm_guest_init(void)
+{
+ int rc;
+
+ rc = paravirt_alloc_area();
+ if (rc)
+ return rc;
+
+ rc = paravirt_initialize();
+ if (rc)
+ goto err;
+
+ paravirt_ops_setup();
+
+ return rc;
+
+ err:
+ paravirt_free_area();
+ return rc;
+}
+
+/* FIXME: need a better solution! */
+core_initcall(kvm_guest_init);
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 633c2ed..f7a0e6e 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -43,6 +43,7 @@
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <linux/smp.h>
+#include <linux/kvm_para.h>

#include "x86_emulate.h"
#include "segment_descriptor.h"
@@ -91,6 +92,11 @@ struct vfsmount *kvmfs_mnt;
#define CR8_RESEVED_BITS (~0x0fULL)
#define EFER_RESERVED_BITS 0xfffffffffffff2fe

+#define KVM_PARAVIRT_FEATURES \
+ (KVM_FEATURE_VMCA | KVM_FEATURE_NOP_IO_DELAY)
+
+#define KVM_MSR_SET_VMCA 0x87655678
+
#ifdef CONFIG_X86_64
// LDT or TSS descriptor in the GDT. 16 bytes.
struct segment_descriptor_64 {
@@ -1340,12 +1346,19 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_emulate_halt);

+static int dispatch_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
+ unsigned long p1, unsigned long p2,
+ unsigned long p3, unsigned long p4)
+{
+ return -ENOSYS;
+}
+
int kvm_hypercall(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
unsigned long nr, a0, a1, a2, a3, a4, a5, ret;

kvm_arch_ops->cache_regs(vcpu);
- ret = -KVM_EINVAL;
+ ret = -EINVAL;
#ifdef CONFIG_X86_64
if (is_long_mode(vcpu)) {
nr = vcpu->regs[VCPU_REGS_RAX];
@@ -1358,16 +1371,17 @@ int kvm_hypercall(struct kvm_vcpu *vcpu, struct kvm_run *run)
} else
#endif
{
- nr = vcpu->regs[VCPU_REGS_RBX] & -1u;
- a0 = vcpu->regs[VCPU_REGS_RAX] & -1u;
+ nr = vcpu->regs[VCPU_REGS_RAX] & -1u;
+ a0 = vcpu->regs[VCPU_REGS_RBX] & -1u;
a1 = vcpu->regs[VCPU_REGS_RCX] & -1u;
a2 = vcpu->regs[VCPU_REGS_RDX] & -1u;
a3 = vcpu->regs[VCPU_REGS_RSI] & -1u;
a4 = vcpu->regs[VCPU_REGS_RDI] & -1u;
a5 = vcpu->regs[VCPU_REGS_RBP] & -1u;
}
- switch (nr) {
- default:
+
+ ret = dispatch_hypercall(vcpu, nr, a0, a1, a2, a3);
+ if (ret == -ENOSYS) {
run->hypercall.args[0] = a0;
run->hypercall.args[1] = a1;
run->hypercall.args[2] = a2;
@@ -1456,7 +1470,7 @@ void realmode_set_cr(struct kvm_vcpu *vcpu, int cr, unsigned long val,
*/
static int vcpu_register_para(struct kvm_vcpu *vcpu, gpa_t para_state_gpa)
{
- struct kvm_vcpu_para_state *para_state;
+ struct kvm_vmca *para_state;
hpa_t para_state_hpa, hypercall_hpa;
struct page *para_state_page;
unsigned char *hypercall;
@@ -1476,30 +1490,14 @@ static int vcpu_register_para(struct kvm_vcpu *vcpu, gpa_t para_state_gpa)
if (is_error_hpa(para_state_hpa))
goto err_gp;

- mark_page_dirty(vcpu->kvm, para_state_gpa >> PAGE_SHIFT);
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;
+ if (is_error_hpa(hypercall_hpa))
goto err_kunmap_skip;
- }

printk(KERN_DEBUG "kvm: para guest successfully registered.\n");
vcpu->para_state_page = para_state_page;
@@ -1512,7 +1510,6 @@ static int vcpu_register_para(struct kvm_vcpu *vcpu, gpa_t para_state_gpa)
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;
@@ -1633,12 +1630,9 @@ 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);
-
+ case KVM_MSR_SET_VMCA:
+ vcpu_register_para(vcpu, data);
+ break;
default:
printk(KERN_ERR "kvm: unhandled wrmsr: 0x%x\n", msr);
return 1;
@@ -1693,6 +1687,20 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)

kvm_arch_ops->cache_regs(vcpu);
function = vcpu->regs[VCPU_REGS_RAX];
+
+ if (function == CPUID_HYPE_IDENT) {
+ vcpu->regs[VCPU_REGS_RAX] = 0;
+ /* KVMKVMKVMKVM */
+ vcpu->regs[VCPU_REGS_RBX] = 0x4b4d564b;
+ vcpu->regs[VCPU_REGS_RCX] = 0x564b4d56;
+ vcpu->regs[VCPU_REGS_RDX] = 0x4d564b4d;
+ goto out;
+ } else if (function == CPUID_HYPE_KVM_FEATURES) {
+ vcpu->regs[VCPU_REGS_RAX] = KVM_MSR_SET_VMCA;
+ vcpu->regs[VCPU_REGS_RDX] = KVM_PARAVIRT_FEATURES;
+ goto out;
+ }
+
vcpu->regs[VCPU_REGS_RAX] = 0;
vcpu->regs[VCPU_REGS_RBX] = 0;
vcpu->regs[VCPU_REGS_RCX] = 0;
@@ -1717,6 +1725,7 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
vcpu->regs[VCPU_REGS_RCX] = best->ecx;
vcpu->regs[VCPU_REGS_RDX] = best->edx;
}
+ out:
kvm_arch_ops->decache_regs(vcpu);
kvm_arch_ops->skip_emulated_instruction(vcpu);
}
diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
index 3b29256..cf51d4a 100644
--- a/include/linux/kvm_para.h
+++ b/include/linux/kvm_para.h
@@ -8,66 +8,26 @@
* 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 CPUID_HYPE_IDENT 0x40000000
+#define CPUID_HYPE_KVM_FEATURES 0x40000001

-#define KVM_PARA_API_VERSION 1
+#define KVM_FEATURE_VMCA (1UL << 0)
+#define KVM_FEATURE_NOP_IO_DELAY (1UL << 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
+struct kvm_vmca
+{
+ u64 hypercall_gpa;
+};

/*
* Hypercall calling convention:
*
- * Each hypercall may have 0-6 parameters.
- *
- * 64-bit hypercall index is in RAX, goes from 0 to __NR_hypercalls-1
- *
- * 64-bit parameters 1-6 are in the standard gcc x86_64 calling convention
- * order: RDI, RSI, RDX, RCX, R8, R9.
+ * Each hypercall may have 0-4 parameters.
*
- * 32-bit index is EBX, parameters are: EAX, ECX, EDX, ESI, EDI, EBP.
- * (the first 3 are according to the gcc regparm calling convention)
+ * 32-bit index is EAX, parameters are: EBX, ECX, EDX, ESI.
*
* No registers are clobbered by the hypercall, except that the
* return value is in RAX.
*/
-#define __NR_hypercalls 0

#endif

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