Merge tag 'kvm-x86-misc-6.11' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.11

 - Add a global struct to consolidate tracking of host values, e.g. EFER, and
   move "shadow_phys_bits" into the structure as "maxphyaddr".

 - Add KVM_CAP_X86_APIC_BUS_CYCLES_NS to allow configuring the effective APIC
   bus frequency, because TDX.

 - Print the name of the APICv/AVIC inhibits in the relevant tracepoint.

 - Clean up KVM's handling of vendor specific emulation to consistently act on
   "compatible with Intel/AMD", versus checking for a specific vendor.

 - Misc cleanups

1 files changed, 57 insertions, 21 deletions

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 6ef7a08b745f..798ad65f4fee 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6483,9 +6483,12 @@ More architecture-specific flags detailing state of the VCPU that may
 affect the device's behavior. Current defined flags::
 
   /* x86, set if the VCPU is in system management mode */
-  #define KVM_RUN_X86_SMM     (1 << 0)
+  #define KVM_RUN_X86_SMM          (1 << 0)
   /* x86, set if bus lock detected in VM */
-  #define KVM_RUN_BUS_LOCK    (1 << 1)
+  #define KVM_RUN_X86_BUS_LOCK     (1 << 1)
+  /* x86, set if the VCPU is executing a nested (L2) guest */
+  #define KVM_RUN_X86_GUEST_MODE   (1 << 2)
+
   /* arm64, set for KVM_EXIT_DEBUG */
   #define KVM_DEBUG_ARCH_HSR_HIGH_VALID  (1 << 0)
 
@@ -7831,29 +7834,31 @@ Valid bits in args[0] are::
   #define KVM_BUS_LOCK_DETECTION_OFF      (1 << 0)
   #define KVM_BUS_LOCK_DETECTION_EXIT     (1 << 1)
 
-Enabling this capability on a VM provides userspace with a way to select
-a policy to handle the bus locks detected in guest. Userspace can obtain
-the supported modes from the result of KVM_CHECK_EXTENSION and define it
-through the KVM_ENABLE_CAP.
+Enabling this capability on a VM provides userspace with a way to select a
+policy to handle the bus locks detected in guest. Userspace can obtain the
+supported modes from the result of KVM_CHECK_EXTENSION and define it through
+the KVM_ENABLE_CAP. The supported modes are mutually-exclusive.
 
-KVM_BUS_LOCK_DETECTION_OFF and KVM_BUS_LOCK_DETECTION_EXIT are supported
-currently and mutually exclusive with each other. More bits can be added in
-the future.
+This capability allows userspace to force VM exits on bus locks detected in the
+guest, irrespective whether or not the host has enabled split-lock detection
+(which triggers an #AC exception that KVM intercepts). This capability is
+intended to mitigate attacks where a malicious/buggy guest can exploit bus
+locks to degrade the performance of the whole system.
 
-With KVM_BUS_LOCK_DETECTION_OFF set, bus locks in guest will not cause vm exits
-so that no additional actions are needed. This is the default mode.
+If KVM_BUS_LOCK_DETECTION_OFF is set, KVM doesn't force guest bus locks to VM
+exit, although the host kernel's split-lock #AC detection still applies, if
+enabled.
 
-With KVM_BUS_LOCK_DETECTION_EXIT set, vm exits happen when bus lock detected
-in VM. KVM just exits to userspace when handling them. Userspace can enforce
-its own throttling or other policy based mitigations.
+If KVM_BUS_LOCK_DETECTION_EXIT is set, KVM enables a CPU feature that ensures
+bus locks in the guest trigger a VM exit, and KVM exits to userspace for all
+such VM exits, e.g. to allow userspace to throttle the offending guest and/or
+apply some other policy-based mitigation. When exiting to userspace, KVM sets
+KVM_RUN_X86_BUS_LOCK in vcpu-run->flags, and conditionally sets the exit_reason
+to KVM_EXIT_X86_BUS_LOCK.
 
-This capability is aimed to address the thread that VM can exploit bus locks to
-degree the performance of the whole system. Once the userspace enable this
-capability and select the KVM_BUS_LOCK_DETECTION_EXIT mode, KVM will set the
-KVM_RUN_BUS_LOCK flag in vcpu-run->flags field and exit to userspace. Concerning
-the bus lock vm exit can be preempted by a higher priority VM exit, the exit
-notifications to userspace can be KVM_EXIT_BUS_LOCK or other reasons.
-KVM_RUN_BUS_LOCK flag is used to distinguish between them.
+Note! Detected bus locks may be coincident with other exits to userspace, i.e.
+KVM_RUN_X86_BUS_LOCK should be checked regardless of the primary exit reason if
+userspace wants to take action on all detected bus locks.
 
 7.23 KVM_CAP_PPC_DAWR1
 ----------------------
@@ -8137,6 +8142,37 @@ error/annotated fault.
 
 See KVM_EXIT_MEMORY_FAULT for more information.
 
+7.35 KVM_CAP_X86_APIC_BUS_CYCLES_NS
+-----------------------------------
+
+:Architectures: x86
+:Target: VM
+:Parameters: args[0] is the desired APIC bus clock rate, in nanoseconds
+:Returns: 0 on success, -EINVAL if args[0] contains an invalid value for the
+          frequency or if any vCPUs have been created, -ENXIO if a virtual
+          local APIC has not been created using KVM_CREATE_IRQCHIP.
+
+This capability sets the VM's APIC bus clock frequency, used by KVM's in-kernel
+virtual APIC when emulating APIC timers.  KVM's default value can be retrieved
+by KVM_CHECK_EXTENSION.
+
+Note: Userspace is responsible for correctly configuring CPUID 0x15, a.k.a. the
+core crystal clock frequency, if a non-zero CPUID 0x15 is exposed to the guest.
+
+7.36 KVM_CAP_X86_GUEST_MODE
+------------------------------
+
+:Architectures: x86
+:Returns: Informational only, -EINVAL on direct KVM_ENABLE_CAP.
+
+The presence of this capability indicates that KVM_RUN will update the
+KVM_RUN_X86_GUEST_MODE bit in kvm_run.flags to indicate whether the
+vCPU was executing nested guest code when it exited.
+
+KVM exits with the register state of either the L1 or L2 guest
+depending on which executed at the time of an exit. Userspace must
+take care to differentiate between these cases.
+
 8. Other capabilities.
 ======================