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From 2cd3e8ceaff90b03db00b7326ba63df8c64c7db8 Mon Sep 17 00:00:00 2001
From: Sudheesh Mavila <sudheesh.mavila@amd.com>
Date: Wed, 15 Aug 2018 08:53:49 +0530
Subject: [PATCH 89/95] KVM: SVM: install RSM intercept
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From 7607b7174405aec7441ff6c970833c463114040a

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@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Sudheesh Mavila <sudheesh.mavila@amd.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 8e60fbc..6352a6c 100755
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -309,6 +309,8 @@ module_param(vgif, int, 0444);
 static int sev = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
 module_param(sev, 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);
@@ -1395,6 +1397,7 @@ 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);
@@ -3707,6 +3710,12 @@ 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;
@@ -4600,7 +4609,7 @@ 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,
 };
-- 
2.7.4