[Devel] [PATCH RHEL8 COMMIT] kvm/x86: extend info on emualation failure

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.39
------>
commit bdc21a00eacaae53e20ac1fa9e431a9f32a5ae22
Author: Denis Plotnikov <dplotnikov at virtuozzo.com>
Date:   Thu Jun 10 13:32:10 2021 +0300

    kvm/x86: extend info on emualation failure
    
    Patch makes handle emulation failure report the phase where
    the failure occur: on decoding or on emulation.
    
    This is for bugs debugging like
    https://jira.sw.ru/browse/PSBM-99553
    
    Signed-off-by: Denis Plotnikov <dplotnikov at virtuozzo.com>
    (cherry-picked from vz7 commit c4f456a14a56 ("kvm/x86: extend info on emualation
    failure"))
    
    https://jira.sw.ru/browse/PSBM-127849
    Signed-off-by: Valeriy Vdovin <valeriy.vdovin at virtuozzo.com>
---
 arch/x86/kvm/x86.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8415bd3d04f5..8a25cd9130cb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6504,10 +6504,11 @@ void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip)
 }
 EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt);
 
-static void printk_emulation_data(struct kvm_vcpu *vcpu, int emulation_type)
+static void printk_emulation_data(struct kvm_vcpu *vcpu, int emulation_type,
+				  bool decoding)
 {
 	struct x86_emulate_ctxt *ctx = vcpu->arch.emulate_ctxt;
-	int i;
+	uint64_t i;
 
 	vcpu_err(vcpu, "=== emulation failure ===\n");
 
@@ -6515,6 +6516,8 @@ static void printk_emulation_data(struct kvm_vcpu *vcpu, int emulation_type)
 
 	vcpu_err(vcpu, "emulation context data (emulation_type: 0x%x)\n",
 		emulation_type);
+	vcpu_err(vcpu, "failed phase: %s\n",
+		decoding ? "decoding" : "emulation");
 	vcpu_err(vcpu, "eflags: 0x%lx start_eip: 0x%lx mode: %d\n",
 		ctx->eflags, ctx->eip, ctx->mode);
 	vcpu_err(vcpu, "opcode_len: %u b: 0x%x op_bytes: %u ad_bytes: %u\n",
@@ -6522,17 +6525,21 @@ static void printk_emulation_data(struct kvm_vcpu *vcpu, int emulation_type)
 	vcpu_err(vcpu, "d: 0x%llx current_eip: 0x%lx\n ", ctx->d, ctx->_eip);
 	vcpu_err(vcpu, "fetch data: data: %p ptr %p pos %p\n",
 		ctx->fetch.data, ctx->fetch.ptr, ctx->fetch.end);
+	vcpu_err(vcpu, "have excpetion: %s\n",
+		ctx->have_exception ? "yes" : "no");
+
 	vcpu_err(vcpu, "fetch data content: ");
 
 	for (i = 0; i < ARRAY_SIZE(ctx->fetch.data); i++) {
 		printk("0x%02x ", ctx->fetch.data[i]);
 	}
-	printk("\n");
+	vcpu_err(vcpu, "\n");
 
 	vcpu_err(vcpu, "=== end of emulation failure ===\n");
 }
 
-static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
+static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type,
+				    bool decoding)
 {
 	++vcpu->stat.insn_emulation_fail;
 	trace_kvm_emulate_insn_failed(vcpu);
@@ -6546,7 +6553,7 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
 		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 		vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
 		vcpu->run->internal.ndata = 0;
-		printk_emulation_data(vcpu, emulation_type);
+		printk_emulation_data(vcpu, emulation_type, decoding);
 		return 0;
 	}
 
@@ -6883,7 +6890,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 				inject_emulated_exception(vcpu);
 				return 1;
 			}
-			return handle_emulation_failure(vcpu, emulation_type);
+			return handle_emulation_failure(vcpu, emulation_type,
+							true);
 		}
 	}
 
@@ -6940,7 +6948,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 					emulation_type))
 			return 1;
 
-		return handle_emulation_failure(vcpu, emulation_type);
+		return handle_emulation_failure(vcpu, emulation_type, false);
 	}
 
 	if (ctxt->have_exception) {