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- From 810253988e9e317d6e576ebe608a5454f274b8fc Mon Sep 17 00:00:00 2001
- From: Maxim Levitsky <[email protected]>
- Date: Tue, 25 Oct 2022 15:47:41 +0300
- Subject: [PATCH] KVM: x86: 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 <[email protected]>
- ---
- arch/x86/kvm/smm.c | 24 +++++++++++++++++++++---
- arch/x86/kvm/smm.h | 5 +++--
- 2 files changed, 24 insertions(+), 5 deletions(-)
- diff --git a/arch/x86/kvm/smm.c b/arch/x86/kvm/smm.c
- index 82761384a866..46d2656937a7 100644
- --- a/arch/x86/kvm/smm.c
- +++ b/arch/x86/kvm/smm.c
- @@ -21,6 +21,7 @@ static void check_smram_offsets(void)
- CHECK_SMRAM32_OFFSET(smbase, 0xFEF8);
- CHECK_SMRAM32_OFFSET(smm_revision, 0xFEFC);
- CHECK_SMRAM32_OFFSET(reserved2, 0xFF00);
- + CHECK_SMRAM32_OFFSET(int_shadow, 0xFF10);
- CHECK_SMRAM32_OFFSET(cr4, 0xFF14);
- CHECK_SMRAM32_OFFSET(reserved3, 0xFF18);
- CHECK_SMRAM32_OFFSET(ds, 0xFF2C);
- @@ -65,7 +66,7 @@ static void check_smram_offsets(void)
- CHECK_SMRAM64_OFFSET(io_restart_rsi, 0xFEB0);
- CHECK_SMRAM64_OFFSET(io_restart_rdi, 0xFEB8);
- CHECK_SMRAM64_OFFSET(io_restart_dword, 0xFEC0);
- - CHECK_SMRAM64_OFFSET(reserved1, 0xFEC4);
- + CHECK_SMRAM64_OFFSET(int_shadow, 0xFEC4);
- CHECK_SMRAM64_OFFSET(io_inst_restart, 0xFEC8);
- CHECK_SMRAM64_OFFSET(auto_hlt_restart, 0xFEC9);
- CHECK_SMRAM64_OFFSET(reserved2, 0xFECA);
- @@ -212,6 +213,8 @@ static void enter_smm_save_state_32(struct kvm_vcpu *vcpu,
- 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
- @@ -261,6 +264,8 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu,
- 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
-
- @@ -306,6 +311,8 @@ 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;
- @@ -453,7 +460,7 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
- {
- struct kvm_vcpu *vcpu = ctxt->vcpu;
- struct desc_ptr dt;
- - int i;
- + int i, r;
-
- ctxt->eflags = smstate->eflags | X86_EFLAGS_FIXED;
- ctxt->_eip = smstate->eip;
- @@ -487,8 +494,16 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
-
- vcpu->arch.smbase = smstate->smbase;
-
- - return rsm_enter_protected_mode(vcpu, smstate->cr0,
- + r = rsm_enter_protected_mode(vcpu, smstate->cr0,
- smstate->cr3, smstate->cr4);
- +
- + if (r != X86EMUL_CONTINUE)
- + return r;
- +
- + static_call(kvm_x86_set_interrupt_shadow)(vcpu, 0);
- + ctxt->interruptibility = (u8)smstate->int_shadow;
- +
- + return r;
- }
-
- #ifdef CONFIG_X86_64
- @@ -539,6 +554,9 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
- rsm_load_seg_64(vcpu, &smstate->fs, VCPU_SREG_FS);
- rsm_load_seg_64(vcpu, &smstate->gs, VCPU_SREG_GS);
-
- + static_call(kvm_x86_set_interrupt_shadow)(vcpu, 0);
- + ctxt->interruptibility = (u8)smstate->int_shadow;
- +
- return X86EMUL_CONTINUE;
- }
- #endif
- diff --git a/arch/x86/kvm/smm.h b/arch/x86/kvm/smm.h
- index 8d96bff3f4d5..2eaec53bcc95 100644
- --- a/arch/x86/kvm/smm.h
- +++ b/arch/x86/kvm/smm.h
- @@ -19,7 +19,8 @@ struct kvm_smram_state_32 {
- u32 reserved1[62];
- u32 smbase;
- u32 smm_revision;
- - u32 reserved2[5];
- + u32 reserved2[4];
- + u32 int_shadow; /* KVM extension */
- u32 cr4; /* CR4 is not present in Intel/AMD SMRAM image */
- u32 reserved3[5];
-
- @@ -86,7 +87,7 @@ struct kvm_smram_state_64 {
- u64 io_restart_rsi;
- u64 io_restart_rdi;
- u32 io_restart_dword;
- - u32 reserved1;
- + u32 int_shadow;
- u8 io_inst_restart;
- u8 auto_hlt_restart;
- u8 reserved2[6];
- --
- 2.38.1
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