From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 28 Jul 2025 15:13:57 +0000 (-0400)
Subject: Merge tag 'kvm-x86-misc-6.17' of https://github.com/kvm-x86/linux into HEAD
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1a14928e2e91a098c6117ba52b06327e3fc5072c;p=thirdparty%2Fkernel%2Flinux.git

Merge tag 'kvm-x86-misc-6.17' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.17

 - Prevert the host's DEBUGCTL.FREEZE_IN_SMM (Intel only) when running the
   guest.  Failure to honor FREEZE_IN_SMM can bleed host state into the guest.

 - Explicitly check vmcs12.GUEST_DEBUGCTL on nested VM-Enter (Intel only) to
   prevent L1 from running L2 with features that KVM doesn't support, e.g. BTF.

 - Intercept SPEC_CTRL on AMD if the MSR shouldn't exist according to the
   vCPU's CPUID model.

 - Rework the MSR interception code so that the SVM and VMX APIs are more or
   less identical.

 - Recalculate all MSR intercepts from the "source" on MSR filter changes, and
   drop the dedicated "shadow" bitmaps (and their awful "max" size defines).

 - WARN and reject loading kvm-amd.ko instead of panicking the kernel if the
   nested SVM MSRPM offsets tracker can't handle an MSR.

 - Advertise support for LKGS (Load Kernel GS base), a new instruction that's
   loosely related to FRED, but is supported and enumerated independently.

 - Fix a user-triggerable WARN that syzkaller found by stuffing INIT_RECEIVED,
   a.k.a. WFS, and then putting the vCPU into VMX Root Mode (post-VMXON).  Use
   the same approach KVM uses for dealing with "impossible" emulation when
   running a !URG guest, and simply wait until KVM_RUN to detect that the vCPU
   has architecturally impossible state.

 - Add KVM_X86_DISABLE_EXITS_APERFMPERF to allow disabling interception of
   APERF/MPERF reads, so that a "properly" configured VM can "virtualize"
   APERF/MPERF (with many caveats).

 - Reject KVM_SET_TSC_KHZ if vCPUs have been created, as changing the "default"
   frequency is unsupported for VMs with a "secure" TSC, and there's no known
   use case for changing the default frequency for other VM types.
---

1a14928e2e91a098c6117ba52b06327e3fc5072c
diff --cc Documentation/virt/kvm/api.rst
index 6f93c8134f95c,dcddef1dd47be..fcb783735dd1b
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@@ -2006,15 -2006,8 +2006,15 @@@ frequency is KHz
  
  If the KVM_CAP_VM_TSC_CONTROL capability is advertised, this can also
  be used as a vm ioctl to set the initial tsc frequency of subsequently
- created vCPUs.
+ created vCPUs.  Note, the vm ioctl is only allowed prior to creating vCPUs.
  
 +For TSC protected Confidential Computing (CoCo) VMs where TSC frequency
 +is configured once at VM scope and remains unchanged during VM's
 +lifetime, the vm ioctl should be used to configure the TSC frequency
 +and the vcpu ioctl is not supported.
 +
 +Example of such CoCo VMs: TDX guests.
 +
  4.56 KVM_GET_TSC_KHZ
  --------------------
  
diff --cc arch/x86/include/asm/kvm_host.h
index bfa6d05d38bc0,f2f641583a503..c3cf1875606b2
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@@ -1408,11 -1392,9 +1408,8 @@@ struct kvm_arch 
  
  	gpa_t wall_clock;
  
- 	bool mwait_in_guest;
- 	bool hlt_in_guest;
- 	bool pause_in_guest;
- 	bool cstate_in_guest;
+ 	u64 disabled_exits;
  
 -	unsigned long irq_sources_bitmap;
  	s64 kvmclock_offset;
  
  	/*
diff --cc arch/x86/kvm/x86.c
index f641903659e9a,a247f67954eab..9ea2e54e75655
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@@ -10920,12 -11046,22 +10924,22 @@@ static int vcpu_enter_guest(struct kvm_
  		set_debugreg(vcpu->arch.eff_db[3], 3);
  		/* When KVM_DEBUGREG_WONT_EXIT, dr6 is accessible in guest. */
  		if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT))
- 			kvm_x86_call(set_dr6)(vcpu, vcpu->arch.dr6);
+ 			run_flags |= KVM_RUN_LOAD_GUEST_DR6;
  	} else if (unlikely(hw_breakpoint_active())) {
 -		set_debugreg(0, 7);
 +		set_debugreg(DR7_FIXED_1, 7);
  	}
  
- 	vcpu->arch.host_debugctl = get_debugctlmsr();
+ 	/*
+ 	 * Refresh the host DEBUGCTL snapshot after disabling IRQs, as DEBUGCTL
+ 	 * can be modified in IRQ context, e.g. via SMP function calls.  Inform
+ 	 * vendor code if any host-owned bits were changed, e.g. so that the
+ 	 * value loaded into hardware while running the guest can be updated.
+ 	 */
+ 	debug_ctl = get_debugctlmsr();
+ 	if ((debug_ctl ^ vcpu->arch.host_debugctl) & kvm_x86_ops.HOST_OWNED_DEBUGCTL &&
+ 	    !vcpu->arch.guest_state_protected)
+ 		run_flags |= KVM_RUN_LOAD_DEBUGCTL;
+ 	vcpu->arch.host_debugctl = debug_ctl;
  
  	guest_timing_enter_irqoff();
  
diff --cc tools/testing/selftests/kvm/include/kvm_util.h
index 1ddf85eebd1d0,492f0edc79559..e18d4bb1372fb
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@@ -18,9 -18,10 +18,11 @@@
  #include <asm/atomic.h>
  #include <asm/kvm.h>
  
 +#include <sys/eventfd.h>
  #include <sys/ioctl.h>
  
+ #include <pthread.h>
+ 
  #include "kvm_util_arch.h"
  #include "kvm_util_types.h"
  #include "sparsebit.h"