KVM: Refactor hypercall infrastructure (v3)

This patch refactors the current hypercall infrastructure to better
support live migration and SMP.  It eliminates the hypercall page by
trapping the UD exception that would occur if you used the wrong hypercall
instruction for the underlying architecture and replacing it with the right
one lazily.

A fall-out of this patch is that the unhandled hypercalls no longer trap to
userspace.  There is very little reason though to use a hypercall to
communicate with userspace as PIO or MMIO can be used.  There is no code
in tree that uses userspace hypercalls.

[avi: fix #ud injection on vmx]

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 46 insertions, 110 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index c0f372f1d76..1c662f63b7a 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -39,6 +39,7 @@
 #include <linux/smp.h>
 #include <linux/anon_inodes.h>
 #include <linux/profile.h>
+#include <linux/kvm_para.h>
 
 #include <asm/processor.h>
 #include <asm/msr.h>
@@ -1362,51 +1363,61 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_halt);
 
-int kvm_hypercall(struct kvm_vcpu *vcpu, struct kvm_run *run)
+int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 {
-	unsigned long nr, a0, a1, a2, a3, a4, a5, ret;
+	unsigned long nr, a0, a1, a2, a3, ret;
 
 	kvm_x86_ops->cache_regs(vcpu);
-	ret = -KVM_EINVAL;
-#ifdef CONFIG_X86_64
-	if (is_long_mode(vcpu)) {
-		nr = vcpu->regs[VCPU_REGS_RAX];
-		a0 = vcpu->regs[VCPU_REGS_RDI];
-		a1 = vcpu->regs[VCPU_REGS_RSI];
-		a2 = vcpu->regs[VCPU_REGS_RDX];
-		a3 = vcpu->regs[VCPU_REGS_RCX];
-		a4 = vcpu->regs[VCPU_REGS_R8];
-		a5 = vcpu->regs[VCPU_REGS_R9];
-	} else
-#endif
-	{
-		nr = vcpu->regs[VCPU_REGS_RBX] & -1u;
-		a0 = vcpu->regs[VCPU_REGS_RAX] & -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;
+
+	nr = vcpu->regs[VCPU_REGS_RAX];
+	a0 = vcpu->regs[VCPU_REGS_RBX];
+	a1 = vcpu->regs[VCPU_REGS_RCX];
+	a2 = vcpu->regs[VCPU_REGS_RDX];
+	a3 = vcpu->regs[VCPU_REGS_RSI];
+
+	if (!is_long_mode(vcpu)) {
+		nr &= 0xFFFFFFFF;
+		a0 &= 0xFFFFFFFF;
+		a1 &= 0xFFFFFFFF;
+		a2 &= 0xFFFFFFFF;
+		a3 &= 0xFFFFFFFF;
 	}
+
 	switch (nr) {
 	default:
-		run->hypercall.nr = nr;
-		run->hypercall.args[0] = a0;
-		run->hypercall.args[1] = a1;
-		run->hypercall.args[2] = a2;
-		run->hypercall.args[3] = a3;
-		run->hypercall.args[4] = a4;
-		run->hypercall.args[5] = a5;
-		run->hypercall.ret = ret;
-		run->hypercall.longmode = is_long_mode(vcpu);
-		kvm_x86_ops->decache_regs(vcpu);
-		return 0;
+		ret = -KVM_ENOSYS;
+		break;
 	}
 	vcpu->regs[VCPU_REGS_RAX] = ret;
 	kvm_x86_ops->decache_regs(vcpu);
-	return 1;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_emulate_hypercall);
+
+int kvm_fix_hypercall(struct kvm_vcpu *vcpu)
+{
+	char instruction[3];
+	int ret = 0;
+
+	mutex_lock(&vcpu->kvm->lock);
+
+	/*
+	 * Blow out the MMU to ensure that no other VCPU has an active mapping
+	 * to ensure that the updated hypercall appears atomically across all
+	 * VCPUs.
+	 */
+	kvm_mmu_zap_all(vcpu->kvm);
+
+	kvm_x86_ops->cache_regs(vcpu);
+	kvm_x86_ops->patch_hypercall(vcpu, instruction);
+	if (emulator_write_emulated(vcpu->rip, instruction, 3, vcpu)
+	    != X86EMUL_CONTINUE)
+		ret = -EFAULT;
+
+	mutex_unlock(&vcpu->kvm->lock);
+
+	return ret;
 }
-EXPORT_SYMBOL_GPL(kvm_hypercall);
 
 static u64 mk_cr_64(u64 curr_cr, u32 new_val)
 {
@@ -1474,75 +1485,6 @@ 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;
-
-	mark_page_dirty(vcpu->kvm, para_state_gpa >> PAGE_SHIFT);
-	para_state_page = pfn_to_page(para_state_hpa >> PAGE_SHIFT);
-	para_state = kmap(para_state_page);
-
-	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;
-
-	mark_page_dirty(vcpu->kvm, hypercall_gpa >> PAGE_SHIFT);
-	hypercall = kmap_atomic(pfn_to_page(hypercall_hpa >> PAGE_SHIFT),
-				KM_USER1) + (hypercall_hpa & ~PAGE_MASK);
-	kvm_x86_ops->patch_hypercall(vcpu, hypercall);
-	kunmap_atomic(hypercall, KM_USER1);
-
-	para_state->ret = 0;
-err_kunmap_skip:
-	kunmap(para_state_page);
-	return 0;
-err_gp:
-	return 1;
-}
-
 int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 {
 	u64 data;
@@ -1656,12 +1598,6 @@ 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:
 		pr_unimpl(vcpu, "unhandled wrmsr: 0x%x\n", msr);
 		return 1;