[RFC PATCH] KVM: x86: hyper-v: Inhibit APICv with VP Assist on SPR/EMR

[Eiichi Tsukata <eiichi.tsukata@nutanix.com>]

Running multiple Windows VMs with VP Assis and APICv causes KVM internal
error on Spapphire Rpaids and Emerald Rapids as is reported in [1].
Here Qemu outputs:

  KVM internal error. Suberror: 3
  extra data[0]: 0x000000008000002f
  extra data[1]: 0x0000000000000020
  extra data[2]: 0x0000000000000582
  extra data[3]: 0x0000000000000006
  RAX=0000000000000000 RBX=0000000000000000 RCX=0000000040000070
  RDX=0000000000000000
  RSI=fffffa8001e3db60 RDI=fffffa8002bc8aa0 RBP=fffff88005a91670
  RSP=fffff88005a915c8
  R8 =0000000000000009 R9 =000000000000000b R10=fffff8000264b000
  R11=fffff88005a91750
  R12=fffff88002e40180 R13=fffffa8001e3dc68 R14=fffffa8001e3dc68
  R15=0000000000000002
  RIP=fffff8000271722c RFL=00000046 [---Z-P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
  ES =002b 0000000000000000 ffffffff 00c0f300 DPL=3 DS   [-WA]
  CS =0010 0000000000000000 00000000 00209b00 DPL=0 CS64 [-RA]
  SS =0018 0000000000000000 ffffffff 00c09300 DPL=0 DS   [-WA]
  DS =002b 0000000000000000 ffffffff 00c0f300 DPL=3 DS   [-WA]
  FS =0053 00000000fff9a000 00007c00 0040f300 DPL=3 DS   [-WA]
  GS =002b fffff88002e40000 ffffffff 00c0f300 DPL=3 DS   [-WA]
  LDT=0000 0000000000000000 ffffffff 00c00000
  TR =0040 fffff88002e44ec0 00000067 00008b00 DPL=0 TSS64-busy
  GDT=     fffff88002e4b4c0 0000007f
  IDT=     fffff88002e4b540 00000fff
  CR0=80050031 CR2=00000000002e408e CR3=000000001c6f5000 CR4=000406f8
  DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000
  DR3=0000000000000000
  DR6=00000000fffe07f0 DR7=0000000000000400
  EFER=0000000000000d01
  Code=25 a8 4b 00 00 b9 70 00 00 40 0f ba 32 00 72 06 33 c0 8b d0 <0f> 30
  5a 58 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 cc cc cc cc cc cc
  66 66 0f 1f

As is noted in [1], this issue is considered to be a microcode issue
specific to SPR/EMR.

Disable APICv when guest tries to enable VP Assist page only when it's
running on those problematic CPU models.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=218267 [1]
Signed-off-by: Eiichi Tsukata <eiichi.tsukata@nutanix.com>
---
 arch/x86/include/asm/kvm_host.h |  8 ++++++++
 arch/x86/kvm/hyperv.c           | 13 +++++++++++++
 arch/x86/kvm/vmx/main.c         |  1 +
 3 files changed, 22 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 950a03e0181e..9ff687c7326b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1213,6 +1213,13 @@ enum kvm_apicv_inhibit {
 	 */
 	APICV_INHIBIT_REASON_HYPERV,
 
+	/*
+	 * Using VP Assist and APICv simultaneously on Sapphire Rapids
+	 * or Emerald Rapids causes KVM internal error, which is
+	 * considered to be a microcode issue.
+	 */
+	APICV_INHIBIT_REASON_HYPERV_VP_ASSIST,
+
 	/*
 	 * APIC acceleration is inhibited because the userspace didn't yet
 	 * enable the kernel/split irqchip.
@@ -1285,6 +1292,7 @@ enum kvm_apicv_inhibit {
 #define APICV_INHIBIT_REASONS				\
 	__APICV_INHIBIT_REASON(DISABLED),		\
 	__APICV_INHIBIT_REASON(HYPERV),			\
+	__APICV_INHIBIT_REASON(HYPERV_VP_ASSIST),	\
 	__APICV_INHIBIT_REASON(ABSENT),			\
 	__APICV_INHIBIT_REASON(BLOCKIRQ),		\
 	__APICV_INHIBIT_REASON(PHYSICAL_ID_ALIASED),	\
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 4f0a94346d00..8d5a1f685191 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -36,6 +36,7 @@
 
 #include <asm/apicdef.h>
 #include <asm/mshyperv.h>
+#include <asm/cpu_device_id.h>
 #include <trace/events/kvm.h>
 
 #include "trace.h"
@@ -1550,6 +1551,8 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 	case HV_X64_MSR_VP_ASSIST_PAGE: {
 		u64 gfn;
 		unsigned long addr;
+		struct kvm *kvm = vcpu->kvm;
+		struct cpuinfo_x86 *c = &boot_cpu_data;
 
 		if (!(data & HV_X64_MSR_VP_ASSIST_PAGE_ENABLE)) {
 			hv_vcpu->hv_vapic = data;
@@ -1571,6 +1574,16 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 			return 1;
 		hv_vcpu->hv_vapic = data;
 		kvm_vcpu_mark_page_dirty(vcpu, gfn);
+
+		/*
+		 * Using VP Assist and APICv simultaneously on Sapphire Rapids
+		 * or Emerald Rapids causes KVM internal error, which is
+		 * considered to be a microcode issue.
+		 */
+		if (c->x86_vfm == INTEL_SAPPHIRERAPIDS_X ||
+		    c->x86_vfm == INTEL_EMERALDRAPIDS_X)
+			kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_HYPERV_VP_ASSIST);
+
 		if (kvm_lapic_set_pv_eoi(vcpu,
 					    gfn_to_gpa(gfn) | KVM_MSR_ENABLED,
 					    sizeof(struct hv_vp_assist_page)))
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 0bf35ebe8a1b..a1e7007133a1 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -11,6 +11,7 @@
 	(BIT(APICV_INHIBIT_REASON_DISABLED) |			\
 	 BIT(APICV_INHIBIT_REASON_ABSENT) |			\
 	 BIT(APICV_INHIBIT_REASON_HYPERV) |			\
+	 BIT(APICV_INHIBIT_REASON_HYPERV_VP_ASSIST) |		\
 	 BIT(APICV_INHIBIT_REASON_BLOCKIRQ) |			\
 	 BIT(APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED) |	\
 	 BIT(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) |		\
-- 
2.45.2