[PATCH 09/13] KVM: x86: save/load state on SMM switch

[Paolo Bonzini]

The big ugly one.  This patch adds support for switching in and out of
system management mode, respectively upon receiving KVM_REQ_SMI and upon
executing a RSM instruction.  Both 32- and 64-bit formats are supported
for the SMM state save area.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/cpuid.h   |   8 ++
 arch/x86/kvm/emulate.c | 243 ++++++++++++++++++++++++++++++++++++++++++++++++-
 arch/x86/kvm/x86.c     | 216 ++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 465 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index c3b1ad9fca81..02b67616435d 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -70,6 +70,14 @@ static inline bool guest_cpuid_has_fsgsbase(struct kvm_vcpu *vcpu)
 	return best && (best->ebx & bit(X86_FEATURE_FSGSBASE));
 }
 
+static inline bool guest_cpuid_has_longmode(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpuid_entry2 *best;
+
+	best = kvm_find_cpuid_entry(vcpu, 0x80000001, 0);
+	return best && (best->edx & bit(X86_FEATURE_LM));
+}
+
 static inline bool guest_cpuid_has_osvw(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index f6b641207416..a49606871277 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2262,12 +2262,253 @@ static int em_lseg(struct x86_emulate_ctxt *ctxt)
 	return rc;
 }
 
+static int emulator_has_longmode(struct x86_emulate_ctxt *ctxt)
+{
+	u32 eax, ebx, ecx, edx;
+
+	eax = 0x80000001;
+	ecx = 0;
+	ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx);
+	return edx & bit(X86_FEATURE_LM);
+}
+
+#define get_smstate(type, smbase, offset)				  \
+	({								  \
+	 type __val;							  \
+	 int r = ctxt->ops->read_std(ctxt, smbase + offset, &__val,       \
+				     sizeof(__val), NULL);		  \
+	 if (r != X86EMUL_CONTINUE)					  \
+		 return X86EMUL_UNHANDLEABLE;				  \
+	 __val;								  \
+	})
+
+static void rsm_set_desc_flags(struct desc_struct *desc, u16 flags)
+{
+	desc->g    = (flags >> 15) & 1;
+	desc->d    = (flags >> 14) & 1;
+	desc->l    = (flags >> 13) & 1;
+	desc->avl  = (flags >> 12) & 1;
+	desc->p    = (flags >> 7) & 1;
+	desc->dpl  = (flags >> 5) & 3;
+	desc->s    = (flags >> 4) & 1;
+	desc->type = flags & 15;
+}
+
+static int rsm_load_seg_32(struct x86_emulate_ctxt *ctxt, u64 smbase, int n)
+{
+	struct desc_struct desc;
+	int offset;
+	u16 selector;
+
+	selector = get_smstate(u32, smbase, 0x7fa8 + n * 4);
+
+	if (n < 3)
+		offset = 0x7f84 + n * 12;
+	else
+		offset = 0x7f2c + (n - 3) * 12;
+
+	set_desc_base(&desc,      get_smstate(u32, smbase, offset + 8));
+	set_desc_limit(&desc,     get_smstate(u32, smbase, offset + 4));
+	rsm_set_desc_flags(&desc, get_smstate(u32, smbase, offset));
+	ctxt->ops->set_segment(ctxt, selector, &desc, 0, n);
+	return X86EMUL_CONTINUE;
+}
+
+static int rsm_load_seg_64(struct x86_emulate_ctxt *ctxt, u64 smbase, int n)
+{
+	struct desc_struct desc;
+	int offset;
+	u16 selector;
+	u32 base3;
+
+	offset = 0x7e00 + n * 16;
+
+	selector =                get_smstate(u16, smbase, offset);
+	rsm_set_desc_flags(&desc, get_smstate(u16, smbase, offset + 2));
+	set_desc_limit(&desc,     get_smstate(u32, smbase, offset + 4));
+	set_desc_base(&desc,      get_smstate(u32, smbase, offset + 8));
+	base3 =                   get_smstate(u32, smbase, offset + 12);
+
+	ctxt->ops->set_segment(ctxt, selector, &desc, base3, n);
+	return X86EMUL_CONTINUE;
+}
+
+static int rsm_enter_protected_mode(struct x86_emulate_ctxt *ctxt,
+				     u64 cr0, u64 cr4)
+{
+	int bad;
+
+	/*
+	 * First enable PAE, long mode needs it before CR0.PG = 1 is set.
+	 * Then enable protected mode.	However, PCID cannot be enabled
+	 * if EFER.LMA=0, so set it separately.
+	 */
+	bad = ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PCIDE);
+	if (bad)
+		return X86EMUL_UNHANDLEABLE;
+
+	bad = ctxt->ops->set_cr(ctxt, 0, cr0);
+	if (bad)
+		return X86EMUL_UNHANDLEABLE;
+
+	if (cr4 & X86_CR4_PCIDE) {
+		bad = ctxt->ops->set_cr(ctxt, 4, cr4);
+		if (bad)
+			return X86EMUL_UNHANDLEABLE;
+	}
+
+	return X86EMUL_CONTINUE;
+}
+
+static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt, u64 smbase)
+{
+	struct desc_struct desc;
+	struct desc_ptr dt;
+	u16 selector;
+	u32 val, cr0, cr4;
+	int i;
+
+	cr0 =                      get_smstate(u32, smbase, 0x7ffc);
+	ctxt->ops->set_cr(ctxt, 3, get_smstate(u32, smbase, 0x7ff8));
+	ctxt->eflags =             get_smstate(u32, smbase, 0x7ff4) | X86_EFLAGS_FIXED;
+	ctxt->_eip =               get_smstate(u32, smbase, 0x7ff0);
+
+	for (i = 0; i < 8; i++)
+		*reg_write(ctxt, i) = get_smstate(u32, smbase, 0x7fd0 + i * 4);
+
+	val = get_smstate(u32, smbase, 0x7fcc);
+	ctxt->ops->set_dr(ctxt, 6, (val & DR6_VOLATILE) | DR6_FIXED_1);
+	val = get_smstate(u32, smbase, 0x7fc8);
+	ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1);
+
+	selector =                 get_smstate(u32, smbase, 0x7fc4);
+	set_desc_base(&desc,       get_smstate(u32, smbase, 0x7f64));
+	set_desc_limit(&desc,      get_smstate(u32, smbase, 0x7f60));
+	rsm_set_desc_flags(&desc,  get_smstate(u32, smbase, 0x7f5c));
+	ctxt->ops->set_segment(ctxt, selector, &desc, 0, VCPU_SREG_TR);
+
+	selector =                 get_smstate(u32, smbase, 0x7fc0);
+	set_desc_base(&desc,       get_smstate(u32, smbase, 0x7f80));
+	set_desc_limit(&desc,      get_smstate(u32, smbase, 0x7f7c));
+	rsm_set_desc_flags(&desc,  get_smstate(u32, smbase, 0x7f78));
+	ctxt->ops->set_segment(ctxt, selector, &desc, 0, VCPU_SREG_LDTR);
+
+	dt.address =               get_smstate(u32, smbase, 0x7f74);
+	dt.size =                  get_smstate(u32, smbase, 0x7f70);
+	ctxt->ops->set_gdt(ctxt, &dt);
+
+	dt.address =               get_smstate(u32, smbase, 0x7f58);
+	dt.size =                  get_smstate(u32, smbase, 0x7f54);
+	ctxt->ops->set_idt(ctxt, &dt);
+
+	for (i = 0; i < 6; i++) {
+		int r = rsm_load_seg_32(ctxt, smbase, i);
+		if (r != X86EMUL_CONTINUE)
+			return r;
+	}
+
+	cr4 = get_smstate(u32, smbase, 0x7f14);
+
+	ctxt->ops->set_smbase(ctxt, get_smstate(u32, smbase, 0x7ef8));
+
+	return rsm_enter_protected_mode(ctxt, cr0, cr4);
+}
+
+static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt, u64 smbase)
+{
+	struct desc_struct desc;
+	struct desc_ptr dt;
+	u64 val, cr0, cr4;
+	u32 base3;
+	u16 selector;
+	int i;
+
+	for (i = 0; i < 16; i++)
+		*reg_write(ctxt, i) = get_smstate(u64, smbase, 0x7ff8 - i * 8);
+
+	ctxt->_eip   = get_smstate(u64, smbase, 0x7f78);
+	ctxt->eflags = get_smstate(u32, smbase, 0x7f70) | X86_EFLAGS_FIXED;
+
+	val = get_smstate(u32, smbase, 0x7f68);
+	ctxt->ops->set_dr(ctxt, 6, (val & DR6_VOLATILE) | DR6_FIXED_1);
+	val = get_smstate(u32, smbase, 0x7f60);
+	ctxt->ops->set_dr(ctxt, 7, (val & DR7_VOLATILE) | DR7_FIXED_1);
+
+	cr0 =                       get_smstate(u64, smbase, 0x7f58);
+	ctxt->ops->set_cr(ctxt, 3,  get_smstate(u64, smbase, 0x7f50));
+	cr4 =                       get_smstate(u64, smbase, 0x7f48);
+	ctxt->ops->set_smbase(ctxt, get_smstate(u32, smbase, 0x7f00));
+	val =                       get_smstate(u64, smbase, 0x7ed0);
+	ctxt->ops->set_msr(ctxt, MSR_EFER, val & ~EFER_LMA);
+
+	selector =                  get_smstate(u32, smbase, 0x7e90);
+	rsm_set_desc_flags(&desc,   get_smstate(u32, smbase, 0x7e92));
+	set_desc_limit(&desc,       get_smstate(u32, smbase, 0x7e94));
+	set_desc_base(&desc,        get_smstate(u32, smbase, 0x7e98));
+	base3 =                     get_smstate(u32, smbase, 0x7e9c);
+	ctxt->ops->set_segment(ctxt, selector, &desc, base3, VCPU_SREG_TR);
+
+	dt.size =                   get_smstate(u32, smbase, 0x7e84);
+	dt.address =                get_smstate(u64, smbase, 0x7e88);
+	ctxt->ops->set_idt(ctxt, &dt);
+
+	selector =                  get_smstate(u32, smbase, 0x7e70);
+	rsm_set_desc_flags(&desc,   get_smstate(u32, smbase, 0x7e72));
+	set_desc_limit(&desc,       get_smstate(u32, smbase, 0x7e74));
+	set_desc_base(&desc,        get_smstate(u32, smbase, 0x7e78));
+	base3 =                     get_smstate(u32, smbase, 0x7e7c);
+	ctxt->ops->set_segment(ctxt, selector, &desc, base3, VCPU_SREG_LDTR);
+
+	dt.size =                   get_smstate(u32, smbase, 0x7e64);
+	dt.address =                get_smstate(u64, smbase, 0x7e68);
+	ctxt->ops->set_gdt(ctxt, &dt);
+
+	for (i = 0; i < 6; i++) {
+		int r = rsm_load_seg_64(ctxt, smbase, i);
+		if (r != X86EMUL_CONTINUE)
+			return r;
+	}
+
+	return rsm_enter_protected_mode(ctxt, cr0, cr4);
+}
+
 static int em_rsm(struct x86_emulate_ctxt *ctxt)
 {
+	unsigned long cr0, cr4, efer;
+	u64 smbase;
+	int ret;
+
+	printk("rsm\n");
 	if ((ctxt->emul_flags & X86EMUL_SMM_MASK) == 0)
 		return emulate_ud(ctxt);
 
-	return X86EMUL_UNHANDLEABLE;
+	/*
+	 * Get back to real mode, to prepare a safe state in which
+	 * to load CR0/CR3/CR4/EFER.  Also this will ensure that
+	 * addresses passed to read_std/write_std are not virtual.
+	 */
+	cr0 = ctxt->ops->get_cr(ctxt, 0);
+	if (cr0 & X86_CR0_PE)
+		ctxt->ops->set_cr(ctxt, 0, cr0 & ~(X86_CR0_PG | X86_CR0_PE));
+	cr4 = ctxt->ops->get_cr(ctxt, 4);
+	if (cr0 & X86_CR4_PAE)
+		ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PAE);
+	efer = 0;
+	ctxt->ops->set_msr(ctxt, MSR_EFER, efer);
+
+	ctxt->ops->get_msr(ctxt, MSR_IA32_SMBASE, &smbase);
+	if (emulator_has_longmode(ctxt))
+		ret = rsm_load_state_64(ctxt, smbase + 0x8000);
+	else
+		ret = rsm_load_state_32(ctxt, smbase + 0x8000);
+
+	if (ret != X86EMUL_CONTINUE) {
+		/* FIXME: should triple fault */
+		return X86EMUL_UNHANDLEABLE;
+	}
+
+	ctxt->emul_flags &= ~X86EMUL_SMM_MASK;
+	return X86EMUL_CONTINUE;
 }
 
 static void
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4cd7a2a18e93..ab6a38617813 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6232,12 +6232,226 @@ static void process_nmi(struct kvm_vcpu *vcpu)
 	kvm_make_request(KVM_REQ_EVENT, vcpu);
 }
 
+#define put_smstate(type, buf, offset, val)			  \
+	*(type *)((buf) + (offset) - 0x7e00) = val
+
+static u16 process_smi_get_segment_flags(struct kvm_segment *seg)
+{
+	u16 flags = 0;
+	flags |= seg->g       << 15;
+	flags |= seg->db      << 14;
+	flags |= seg->l       << 13;
+	flags |= seg->avl     << 12;
+	flags |= seg->present << 7;
+	flags |= seg->dpl     << 5;
+	flags |= seg->s       << 4;
+	flags |= seg->type;
+	return flags;
+}
+
+static void process_smi_save_seg_32(struct kvm_vcpu *vcpu, char *buf, int n)
+{
+	struct kvm_segment seg;
+	int offset;
+
+	kvm_get_segment(vcpu, &seg, n);
+	put_smstate(u32, buf, 0x7fa8 + n * 4, seg.selector);
+
+	if (n < 3)
+		offset = 0x7f84 + n * 12;
+	else
+		offset = 0x7f2c + (n - 3) * 12;
+
+	put_smstate(u32, buf, offset + 8, seg.base);
+	put_smstate(u32, buf, offset + 4, seg.limit);
+	put_smstate(u32, buf, offset, process_smi_get_segment_flags(&seg));
+}
+
+static void process_smi_save_seg_64(struct kvm_vcpu *vcpu, char *buf, int n)
+{
+	struct kvm_segment seg;
+	int offset;
+
+	kvm_get_segment(vcpu, &seg, n);
+	offset = 0x7e00 + n * 16;
+
+	put_smstate(u16, buf, offset, seg.selector);
+	put_smstate(u16, buf, offset + 2, process_smi_get_segment_flags(&seg));
+	put_smstate(u32, buf, offset + 4, seg.limit);
+	put_smstate(u64, buf, offset + 8, seg.base);
+}
+
+static void process_smi_save_state_32(struct kvm_vcpu *vcpu, char *buf)
+{
+	struct desc_ptr dt;
+	struct kvm_segment seg;
+	unsigned long val;
+	int i;
+
+	put_smstate(u32, buf, 0x7ffc, kvm_read_cr0(vcpu));
+	put_smstate(u32, buf, 0x7ff8, kvm_read_cr3(vcpu));
+	put_smstate(u32, buf, 0x7ff4, kvm_get_rflags(vcpu));
+	put_smstate(u32, buf, 0x7ff0, kvm_rip_read(vcpu));
+
+	for (i = 0; i < 8; i++)
+		put_smstate(u32, buf, 0x7fd0 + i * 4, kvm_register_read(vcpu, i));
+
+	kvm_get_dr(vcpu, 6, &val);
+	put_smstate(u32, buf, 0x7fcc, (u32)val);
+	kvm_get_dr(vcpu, 7, &val);
+	put_smstate(u32, buf, 0x7fc8, (u32)val);
+
+	kvm_get_segment(vcpu, &seg, VCPU_SREG_TR);
+	put_smstate(u32, buf, 0x7fc4, seg.selector);
+	put_smstate(u32, buf, 0x7f64, seg.base);
+	put_smstate(u32, buf, 0x7f60, seg.limit);
+	put_smstate(u32, buf, 0x7f5c, process_smi_get_segment_flags(&seg));
+
+	kvm_get_segment(vcpu, &seg, VCPU_SREG_LDTR);
+	put_smstate(u32, buf, 0x7fc0, seg.selector);
+	put_smstate(u32, buf, 0x7f80, seg.base);
+	put_smstate(u32, buf, 0x7f7c, seg.limit);
+	put_smstate(u32, buf, 0x7f78, process_smi_get_segment_flags(&seg));
+
+	kvm_x86_ops->get_gdt(vcpu, &dt);
+	put_smstate(u32, buf, 0x7f74, dt.address);
+	put_smstate(u32, buf, 0x7f70, dt.size);
+
+	kvm_x86_ops->get_idt(vcpu, &dt);
+	put_smstate(u32, buf, 0x7f58, dt.address);
+	put_smstate(u32, buf, 0x7f54, dt.size);
+
+	for (i = 0; i < 6; i++)
+		process_smi_save_seg_32(vcpu, buf, i);
+
+	put_smstate(u32, buf, 0x7f14, kvm_read_cr4(vcpu));
+
+	/* revision id */
+	put_smstate(u32, buf, 0x7efc, 0x00020000);
+	put_smstate(u32, buf, 0x7ef8, vcpu->arch.smbase);
+}
+
+static void process_smi_save_state_64(struct kvm_vcpu *vcpu, char *buf)
+{
+#ifdef CONFIG_X86_64
+	struct desc_ptr dt;
+	struct kvm_segment seg;
+	unsigned long val;
+	int i;
+
+	for (i = 0; i < 16; i++)
+		put_smstate(u64, buf, 0x7ff8 - i * 8, kvm_register_read(vcpu, i));
+
+	put_smstate(u64, buf, 0x7f78, kvm_rip_read(vcpu));
+	put_smstate(u32, buf, 0x7f70, kvm_get_rflags(vcpu));
+
+	kvm_get_dr(vcpu, 6, &val);
+	put_smstate(u64, buf, 0x7f68, val);
+	kvm_get_dr(vcpu, 7, &val);
+	put_smstate(u64, buf, 0x7f60, val);
+
+	put_smstate(u64, buf, 0x7f58, kvm_read_cr0(vcpu));
+	put_smstate(u64, buf, 0x7f50, kvm_read_cr3(vcpu));
+	put_smstate(u64, buf, 0x7f48, kvm_read_cr4(vcpu));
+
+	put_smstate(u32, buf, 0x7f00, vcpu->arch.smbase);
+
+	/* revision id */
+	put_smstate(u32, buf, 0x7efc, 0x00020064);
+
+	put_smstate(u64, buf, 0x7ed0, vcpu->arch.efer);
+
+	kvm_get_segment(vcpu, &seg, VCPU_SREG_TR);
+	put_smstate(u16, buf, 0x7e90, seg.selector);
+	put_smstate(u16, buf, 0x7e92, process_smi_get_segment_flags(&seg));
+	put_smstate(u32, buf, 0x7e94, seg.limit);
+	put_smstate(u64, buf, 0x7e98, seg.base);
+
+	kvm_x86_ops->get_idt(vcpu, &dt);
+	put_smstate(u32, buf, 0x7e84, dt.size);
+	put_smstate(u64, buf, 0x7e88, dt.address);
+
+	kvm_get_segment(vcpu, &seg, VCPU_SREG_LDTR);
+	put_smstate(u16, buf, 0x7e70, seg.selector);
+	put_smstate(u16, buf, 0x7e72, process_smi_get_segment_flags(&seg));
+	put_smstate(u32, buf, 0x7e74, seg.limit);
+	put_smstate(u64, buf, 0x7e78, seg.base);
+
+	kvm_x86_ops->get_gdt(vcpu, &dt);
+	put_smstate(u32, buf, 0x7e64, dt.size);
+	put_smstate(u64, buf, 0x7e68, dt.address);
+
+	for (i = 0; i < 6; i++)
+		process_smi_save_seg_64(vcpu, buf, i);
+#else
+	WARN_ON_ONCE(1);
+#endif
+}
+
 static void process_smi(struct kvm_vcpu *vcpu)
 {
+	struct kvm_segment cs, ds;
+	char buf[512];
+	u32 cr0;
+	int r;
+
 	if (is_smm(vcpu))
 		return;
 
-	printk_once(KERN_DEBUG "Ignoring guest SMI\n");
+	printk("smm %llx\n", vcpu->arch.smbase);
+	vcpu->arch.hflags |= HF_SMM_MASK;
+	memset(buf, 0, 512);
+	if (guest_cpuid_has_longmode(vcpu))
+		process_smi_save_state_64(vcpu, buf);
+	else
+		process_smi_save_state_32(vcpu, buf);
+
+	r = kvm_write_guest(vcpu->kvm, vcpu->arch.smbase + 0xfe00, buf, sizeof(buf));
+	if (r < 0)
+		return;
+
+	kvm_x86_ops->set_nmi_mask(vcpu, true);
+	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
+	kvm_rip_write(vcpu, 0x8000);
+
+	cr0 = vcpu->arch.cr0 & ~(X86_CR0_PE | X86_CR0_EM | X86_CR0_TS | X86_CR0_PG);
+	kvm_x86_ops->set_cr0(vcpu, cr0);
+	vcpu->arch.cr0 = cr0;
+
+	kvm_x86_ops->set_cr4(vcpu, 0);
+
+	__kvm_set_dr(vcpu, 7, DR7_FIXED_1);
+
+	cs.selector = (vcpu->arch.smbase >> 4) & 0xffff;
+	cs.base = vcpu->arch.smbase;
+
+	ds.selector = 0;
+	ds.base = 0;
+
+	cs.limit    = ds.limit = 0xffffffff;
+	cs.type     = ds.type = 0x3;
+	cs.dpl      = ds.dpl = 0;
+	cs.db       = ds.db = 0;
+	cs.s        = ds.s = 1;
+	cs.l        = ds.l = 0;
+	cs.g        = ds.g = 1;
+	cs.avl      = ds.avl = 0;
+	cs.present  = ds.present = 1;
+	cs.unusable = ds.unusable = 0;
+	cs.padding  = ds.padding = 0;
+
+	kvm_set_segment(vcpu, &cs, VCPU_SREG_CS);
+	kvm_set_segment(vcpu, &ds, VCPU_SREG_DS);
+	kvm_set_segment(vcpu, &ds, VCPU_SREG_ES);
+	kvm_set_segment(vcpu, &ds, VCPU_SREG_FS);
+	kvm_set_segment(vcpu, &ds, VCPU_SREG_GS);
+	kvm_set_segment(vcpu, &ds, VCPU_SREG_SS);
+
+	if (guest_cpuid_has_longmode(vcpu))
+		kvm_x86_ops->set_efer(vcpu, 0);
+
+	kvm_update_cpuid(vcpu);
+	kvm_mmu_reset_context(vcpu);
 }
 
 static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
-- 
1.8.3.1


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