APPLIED: [PATCH 1/2][Bionic] KVM: SVM: install RSM intercept

[Khaled Elmously]

On 2019-08-29 14:06:57 , Rafael David Tinoco wrote:
> From: Brijesh Singh <brijesh.singh at amd.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1834522
> 
> RSM instruction is used by the SMM handler to return from SMM mode.
> Currently, rsm causes a #UD - which results in instruction fetch,
> decode, and emulate. By installing the RSM intercept we can avoid the
> instruction fetch since we know that #VMEXIT was due to rsm.
> 
> The patch is required for the SEV guest, because in case of SEV guest
> memory is encrypted with guest-specific key and hypervisor will not able
> to fetch the instruction bytes from the guest memory.
> 
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Radim Krčmář <rkrcmar at redhat.com>
> Cc: Joerg Roedel <joro at 8bytes.org>
> Cc: Borislav Petkov <bp at suse.de>
> Cc: Tom Lendacky <thomas.lendacky at amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> (cherry-picked from commit 7607b7174405aec7441ff6c970833c463114040a)
> Signed-off-by: Rafael David Tinoco <rafaeldtinoco at ubuntu.com>
> 
> ---
>  arch/x86/kvm/svm.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 72765bbac9f1..538ca5446cfd 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -298,6 +298,8 @@ module_param(vls, int, 0444);
>  static int vgif = true;
>  module_param(vgif, int, 0444);
>  
> +static u8 rsm_ins_bytes[] = "\x0f\xaa";
> +
>  static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);
>  static void svm_flush_tlb(struct kvm_vcpu *vcpu);
>  static void svm_complete_interrupts(struct vcpu_svm *svm);
> @@ -1292,6 +1294,7 @@ static void init_vmcb(struct vcpu_svm *svm)
>  	set_intercept(svm, INTERCEPT_SKINIT);
>  	set_intercept(svm, INTERCEPT_WBINVD);
>  	set_intercept(svm, INTERCEPT_XSETBV);
> +	set_intercept(svm, INTERCEPT_RSM);
>  
>  	if (!kvm_mwait_in_guest()) {
>  		set_intercept(svm, INTERCEPT_MONITOR);
> @@ -3441,6 +3444,12 @@ static int emulate_on_interception(struct vcpu_svm *svm)
>  	return emulate_instruction(&svm->vcpu, 0) == EMULATE_DONE;
>  }
>  
> +static int rsm_interception(struct vcpu_svm *svm)
> +{
> +	return x86_emulate_instruction(&svm->vcpu, 0, 0,
> +				       rsm_ins_bytes, 2) == EMULATE_DONE;
> +}
> +
>  static int rdpmc_interception(struct vcpu_svm *svm)
>  {
>  	int err;
> @@ -4327,7 +4336,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
>  	[SVM_EXIT_MWAIT]			= mwait_interception,
>  	[SVM_EXIT_XSETBV]			= xsetbv_interception,
>  	[SVM_EXIT_NPF]				= npf_interception,
> -	[SVM_EXIT_RSM]                          = emulate_on_interception,
> +	[SVM_EXIT_RSM]                          = rsm_interception,
>  	[SVM_EXIT_AVIC_INCOMPLETE_IPI]		= avic_incomplete_ipi_interception,
>  	[SVM_EXIT_AVIC_UNACCELERATED_ACCESS]	= avic_unaccelerated_access_interception,
>  };
> -- 
> 2.17.1
> 
> 
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