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KVM: x86: Save and reload SSP to/from SMRAM

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Save CET SSP to SMRAM on SMI and reload it on RSM. KVM emulates HW arch
behavior when guest enters/leaves SMM mode,i.e., save registers to SMRAM
at the entry of SMM and reload them at the exit to SMM. Per SDM, SSP is
one of such registers on 64-bit Arch, and add the support for SSP.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Tested-by: Mathias Krause <minipli@grsecurity.net>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-16-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Yang Weijiang 2025-09-19 15:32:22 -07:00 • committed by Sean Christopherson
parent 8b59d0275c
commit 1a61bd0d12
2 changed files with 9 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

8
arch/x86/kvm/smm.c
View file

@ -269,6 +269,10 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu,
enter_smm_save_seg_64(vcpu, &smram->gs, VCPU_SREG_GS);
smram->int_shadow = kvm_x86_call(get_interrupt_shadow)(vcpu);
if (guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK) &&
kvm_msr_read(vcpu, MSR_KVM_INTERNAL_GUEST_SSP, &smram->ssp))
kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
}
#endif
@ -558,6 +562,10 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
kvm_x86_call(set_interrupt_shadow)(vcpu, 0);
ctxt->interruptibility = (u8)smstate->int_shadow;
if (guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK) &&
kvm_msr_write(vcpu, MSR_KVM_INTERNAL_GUEST_SSP, smstate->ssp))
return X86EMUL_UNHANDLEABLE;
return X86EMUL_CONTINUE;
}
#endif

2
arch/x86/kvm/smm.h
View file

@ -116,8 +116,8 @@ struct kvm_smram_state_64 {
u32 smbase;
u32 reserved4[5];
/* ssp and svm_* fields below are not implemented by KVM */
u64 ssp;
/* svm_* fields below are not implemented by KVM */
u64 svm_guest_pat;
u64 svm_host_efer;
u64 svm_host_cr4;