[pve-kernel.git] / patches / kernel / 0029-KVM-x86-emulator-smm-preserve-interrupt-shadow-in-SM.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Maxim Levitsky <mlevitsk@redhat.com>
Date: Tue, 21 Jun 2022 18:09:02 +0300
Subject: [PATCH] KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM

When #SMI is asserted, the CPU can be in interrupt shadow
due to sti or mov ss.

It is not mandatory in  Intel/AMD prm to have the #SMI
blocked during the shadow, and on top of
that, since neither SVM nor VMX has true support for SMI
window, waiting for one instruction would mean single stepping
the guest.

Instead, allow #SMI in this case, but both reset the interrupt
window and stash its value in SMRAM to restore it on exit
from SMM.

This fixes rare failures seen mostly on windows guests on VMX,
when #SMI falls on the sti instruction which mainfest in
VM entry failure due to EFLAGS.IF not being set, but STI interrupt
window still being set in the VMCS.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 arch/x86/kvm/emulate.c     | 17 ++++++++++++++---
 arch/x86/kvm/kvm_emulate.h | 13 ++++++++++---
 arch/x86/kvm/x86.c         | 12 ++++++++++++
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index d34ed0475128..f4373213bef8 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2431,7 +2431,7 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
 			     struct kvm_smram_state_32 *smstate)
 {
 	struct desc_ptr dt;
-	int i;
+	int i, r;
 
 	ctxt->eflags =  smstate->eflags | X86_EFLAGS_FIXED;
 	ctxt->_eip =  smstate->eip;
@@ -2466,8 +2466,16 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
 
 	ctxt->ops->set_smbase(ctxt, smstate->smbase);
 
-	return rsm_enter_protected_mode(ctxt, smstate->cr0,
-					smstate->cr3, smstate->cr4);
+	r = rsm_enter_protected_mode(ctxt, smstate->cr0,
+				     smstate->cr3, smstate->cr4);
+
+	if (r != X86EMUL_CONTINUE)
+		return r;
+
+	ctxt->ops->set_int_shadow(ctxt, 0);
+	ctxt->interruptibility = (u8)smstate->int_shadow;
+
+	return X86EMUL_CONTINUE;
 }
 
 #ifdef CONFIG_X86_64
@@ -2516,6 +2524,9 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
 	rsm_load_seg_64(ctxt, &smstate->fs, VCPU_SREG_FS);
 	rsm_load_seg_64(ctxt, &smstate->gs, VCPU_SREG_GS);
 
+	ctxt->ops->set_int_shadow(ctxt, 0);
+	ctxt->interruptibility = (u8)smstate->int_shadow;
+
 	return X86EMUL_CONTINUE;
 }
 #endif
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 3bbf7c1c5b18..e7acf0052389 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -231,6 +231,7 @@ struct x86_emulate_ops {
 	bool (*guest_has_rdpid)(struct x86_emulate_ctxt *ctxt);
 
 	void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
+	void (*set_int_shadow)(struct x86_emulate_ctxt *ctxt, u8 shadow);
 
 	unsigned (*get_hflags)(struct x86_emulate_ctxt *ctxt);
 	void (*exiting_smm)(struct x86_emulate_ctxt *ctxt);
@@ -498,7 +499,9 @@ struct kvm_smram_state_32 {
 	u32 reserved1[62];			/* FE00 - FEF7 */
 	u32 smbase;				/* FEF8 */
 	u32 smm_revision;			/* FEFC */
-	u32 reserved2[5];			/* FF00-FF13 */
+	u32 reserved2[4];			/* FF00-FF0F*/
+	/* int_shadow is KVM extension*/
+	u32 int_shadow;				/* FF10 */
 	/* CR4 is not present in Intel/AMD SMRAM image*/
 	u32 cr4;				/* FF14 */
 	u32 reserved3[5];			/* FF18 */
@@ -570,13 +573,17 @@ struct kvm_smram_state_64 {
 	struct kvm_smm_seg_state_64 idtr;	/* FE80 (R/O) */
 	struct kvm_smm_seg_state_64 tr;		/* FE90 (R/O) */
 
-	/* I/O restart and auto halt restart are not implemented by KVM */
+	/*
+	 * I/O restart and auto halt restart are not implemented by KVM
+	 * int_shadow is KVM's extension
+	 */
+
 	u64 io_restart_rip;			/* FEA0 (R/O) */
 	u64 io_restart_rcx;			/* FEA8 (R/O) */
 	u64 io_restart_rsi;			/* FEB0 (R/O) */
 	u64 io_restart_rdi;			/* FEB8 (R/O) */
 	u32 io_restart_dword;			/* FEC0 (R/O) */
-	u32 reserved1;				/* FEC4 */
+	u32 int_shadow;				/* FEC4 (R/O) */
 	u8 io_instruction_restart;		/* FEC8 (R/W) */
 	u8 auto_halt_restart;			/* FEC9 (R/W) */
 	u8 reserved2[6];			/* FECA-FECF */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f7b2fe174574..2072d994b06f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7840,6 +7840,11 @@ static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
 	static_call(kvm_x86_set_nmi_mask)(emul_to_vcpu(ctxt), masked);
 }
 
+static void emulator_set_int_shadow(struct x86_emulate_ctxt *ctxt, u8 shadow)
+{
+	 static_call(kvm_x86_set_interrupt_shadow)(emul_to_vcpu(ctxt), shadow);
+}
+
 static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
 {
 	return emul_to_vcpu(ctxt)->arch.hflags;
@@ -7911,6 +7916,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.guest_has_fxsr      = emulator_guest_has_fxsr,
 	.guest_has_rdpid     = emulator_guest_has_rdpid,
 	.set_nmi_mask        = emulator_set_nmi_mask,
+	.set_int_shadow      = emulator_set_int_shadow,
 	.get_hflags          = emulator_get_hflags,
 	.exiting_smm         = emulator_exiting_smm,
 	.leave_smm           = emulator_leave_smm,
@@ -9688,6 +9694,8 @@ static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_stat
 	smram->cr4 = kvm_read_cr4(vcpu);
 	smram->smm_revision = 0x00020000;
 	smram->smbase = vcpu->arch.smbase;
+
+	smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
 }
 
 #ifdef CONFIG_X86_64
@@ -9736,6 +9744,8 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, struct kvm_smram_stat
 	enter_smm_save_seg_64(vcpu, &smram->ds, VCPU_SREG_DS);
 	enter_smm_save_seg_64(vcpu, &smram->fs, VCPU_SREG_FS);
 	enter_smm_save_seg_64(vcpu, &smram->gs, VCPU_SREG_GS);
+
+	smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
 }
 #endif
 
@@ -9772,6 +9782,8 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
 	kvm_rip_write(vcpu, 0x8000);
 
+	static_call(kvm_x86_set_interrupt_shadow)(vcpu, 0);
+
 	cr0 = vcpu->arch.cr0 & ~(X86_CR0_PE | X86_CR0_EM | X86_CR0_TS | X86_CR0_PG);
 	static_call(kvm_x86_set_cr0)(vcpu, cr0);
 	vcpu->arch.cr0 = cr0;
Commit	Line	Data
54ebe3cb TL	1	From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
	2	From: Maxim Levitsky <mlevitsk@redhat.com>
	3	Date: Tue, 21 Jun 2022 18:09:02 +0300
	4	Subject: [PATCH] KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM
	5
	6	When #SMI is asserted, the CPU can be in interrupt shadow
	7	due to sti or mov ss.
	8
	9	It is not mandatory in Intel/AMD prm to have the #SMI
	10	blocked during the shadow, and on top of
	11	that, since neither SVM nor VMX has true support for SMI
	12	window, waiting for one instruction would mean single stepping
	13	the guest.
	14
	15	Instead, allow #SMI in this case, but both reset the interrupt
	16	window and stash its value in SMRAM to restore it on exit
	17	from SMM.
	18
	19	This fixes rare failures seen mostly on windows guests on VMX,
	20	when #SMI falls on the sti instruction which mainfest in
	21	VM entry failure due to EFLAGS.IF not being set, but STI interrupt
	22	window still being set in the VMCS.
	23
	24	Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
	25	Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
	26	---
	27	arch/x86/kvm/emulate.c \| 17 ++++++++++++++---
	28	arch/x86/kvm/kvm_emulate.h \| 13 ++++++++++---
	29	arch/x86/kvm/x86.c \| 12 ++++++++++++
	30	3 files changed, 36 insertions(+), 6 deletions(-)
	31
	32	diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
	33	index d34ed0475128..f4373213bef8 100644
	34	--- a/arch/x86/kvm/emulate.c
	35	+++ b/arch/x86/kvm/emulate.c
	36	@@ -2431,7 +2431,7 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
	37	struct kvm_smram_state_32 *smstate)
	38	{
	39	struct desc_ptr dt;
	40	- int i;
	41	+ int i, r;
	42
	43	ctxt->eflags = smstate->eflags \| X86_EFLAGS_FIXED;
	44	ctxt->_eip = smstate->eip;
	45	@@ -2466,8 +2466,16 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
	46
	47	ctxt->ops->set_smbase(ctxt, smstate->smbase);
	48
	49	- return rsm_enter_protected_mode(ctxt, smstate->cr0,
	50	- smstate->cr3, smstate->cr4);
	51	+ r = rsm_enter_protected_mode(ctxt, smstate->cr0,
	52	+ smstate->cr3, smstate->cr4);
	53	+
	54	+ if (r != X86EMUL_CONTINUE)
	55	+ return r;
	56	+
	57	+ ctxt->ops->set_int_shadow(ctxt, 0);
	58	+ ctxt->interruptibility = (u8)smstate->int_shadow;
	59	+
	60	+ return X86EMUL_CONTINUE;
	61	}
	62
	63	#ifdef CONFIG_X86_64
	64	@@ -2516,6 +2524,9 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
65	rsm_load_seg_64(ctxt, &smstate->fs, VCPU_SREG_FS);
66	rsm_load_seg_64(ctxt, &smstate->gs, VCPU_SREG_GS);
67
68	+ ctxt->ops->set_int_shadow(ctxt, 0);
69	+ ctxt->interruptibility = (u8)smstate->int_shadow;
70	+
71	return X86EMUL_CONTINUE;
72	}
73	#endif
74	diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
75	index 3bbf7c1c5b18..e7acf0052389 100644
76	--- a/arch/x86/kvm/kvm_emulate.h
77	+++ b/arch/x86/kvm/kvm_emulate.h
78	@@ -231,6 +231,7 @@ struct x86_emulate_ops {
79	bool (guest_has_rdpid)(struct x86_emulate_ctxt ctxt);
80
81	void (set_nmi_mask)(struct x86_emulate_ctxt ctxt, bool masked);
82	+ void (set_int_shadow)(struct x86_emulate_ctxt ctxt, u8 shadow);
83
84	unsigned (get_hflags)(struct x86_emulate_ctxt ctxt);
85	void (exiting_smm)(struct x86_emulate_ctxt ctxt);
86	@@ -498,7 +499,9 @@ struct kvm_smram_state_32 {
87	u32 reserved1[62]; /* FE00 - FEF7 */
88	u32 smbase; /* FEF8 */
89	u32 smm_revision; /* FEFC */
90	- u32 reserved2[5]; /* FF00-FF13 */
91	+ u32 reserved2[4]; /* FF00-FF0F*/
92	+ /* int_shadow is KVM extension*/
93	+ u32 int_shadow; /* FF10 */
94	/* CR4 is not present in Intel/AMD SMRAM image*/
95	u32 cr4; /* FF14 */
96	u32 reserved3[5]; /* FF18 */
97	@@ -570,13 +573,17 @@ struct kvm_smram_state_64 {
98	struct kvm_smm_seg_state_64 idtr; /* FE80 (R/O) */
99	struct kvm_smm_seg_state_64 tr; /* FE90 (R/O) */
100
101	- /* I/O restart and auto halt restart are not implemented by KVM */
102	+ /*
103	+ * I/O restart and auto halt restart are not implemented by KVM
104	+ * int_shadow is KVM's extension
105	+ */
106	+
107	u64 io_restart_rip; /* FEA0 (R/O) */
108	u64 io_restart_rcx; /* FEA8 (R/O) */
109	u64 io_restart_rsi; /* FEB0 (R/O) */
110	u64 io_restart_rdi; /* FEB8 (R/O) */
111	u32 io_restart_dword; /* FEC0 (R/O) */
112	- u32 reserved1; /* FEC4 */
113	+ u32 int_shadow; /* FEC4 (R/O) */
114	u8 io_instruction_restart; /* FEC8 (R/W) */
115	u8 auto_halt_restart; /* FEC9 (R/W) */
116	u8 reserved2[6]; /* FECA-FECF */
117	diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
118	index f7b2fe174574..2072d994b06f 100644
119	--- a/arch/x86/kvm/x86.c
120	+++ b/arch/x86/kvm/x86.c
121	@@ -7840,6 +7840,11 @@ static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
122	static_call(kvm_x86_set_nmi_mask)(emul_to_vcpu(ctxt), masked);
123	}
124
125	+static void emulator_set_int_shadow(struct x86_emulate_ctxt *ctxt, u8 shadow)
126	+{
127	+ static_call(kvm_x86_set_interrupt_shadow)(emul_to_vcpu(ctxt), shadow);
128	+}
129	+
130	static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
131	{
132	return emul_to_vcpu(ctxt)->arch.hflags;
133	@@ -7911,6 +7916,7 @@ static const struct x86_emulate_ops emulate_ops = {
134	.guest_has_fxsr = emulator_guest_has_fxsr,
135	.guest_has_rdpid = emulator_guest_has_rdpid,
136	.set_nmi_mask = emulator_set_nmi_mask,
137	+ .set_int_shadow = emulator_set_int_shadow,
138	.get_hflags = emulator_get_hflags,
139	.exiting_smm = emulator_exiting_smm,
140	.leave_smm = emulator_leave_smm,
141	@@ -9688,6 +9694,8 @@ static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_stat
142	smram->cr4 = kvm_read_cr4(vcpu);
143	smram->smm_revision = 0x00020000;
144	smram->smbase = vcpu->arch.smbase;
145	+
146	+ smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
147	}
148
149	#ifdef CONFIG_X86_64
150	@@ -9736,6 +9744,8 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, struct kvm_smram_stat
151	enter_smm_save_seg_64(vcpu, &smram->ds, VCPU_SREG_DS);
152	enter_smm_save_seg_64(vcpu, &smram->fs, VCPU_SREG_FS);
153	enter_smm_save_seg_64(vcpu, &smram->gs, VCPU_SREG_GS);
154	+
155	+ smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
156	}
157	#endif
158
159	@@ -9772,6 +9782,8 @@ static void enter_smm(struct kvm_vcpu *vcpu)
160	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
161	kvm_rip_write(vcpu, 0x8000);
162
163	+ static_call(kvm_x86_set_interrupt_shadow)(vcpu, 0);
164	+
165	cr0 = vcpu->arch.cr0 & ~(X86_CR0_PE \| X86_CR0_EM \| X86_CR0_TS \| X86_CR0_PG);
166	static_call(kvm_x86_set_cr0)(vcpu, cr0);
167	vcpu->arch.cr0 = cr0;