linux-toradex.git/include/uapi/linux/kvm.h, branch v5.10-rc3

kvm: x86: only provide PV features if enabled in guest's CPUID

2020-10-21T21:36:32+00:00

KVM unconditionally provides PV features to the guest, regardless of the
configured CPUID. An unwitting guest that doesn't check
KVM_CPUID_FEATURES before use could access paravirt features that
userspace did not intend to provide. Fix this by checking the guest's
CPUID before performing any paravirtual operations.

Introduce a capability, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, to gate the
aforementioned enforcement. Migrating a VM from a host w/o this patch to
a host with this patch could silently change the ABI exposed to the
guest, warranting that we default to the old behavior and opt-in for
the new one.

Reviewed-by: Jim Mattson 
Reviewed-by: Peter Shier 
Signed-off-by: Oliver Upton 
Change-Id: I202a0926f65035b872bfe8ad15307c026de59a98
Message-Id: <20200818152429.1923996-4-oupton@google.com>
Reviewed-by: Wanpeng Li 
Signed-off-by: Paolo Bonzini

KVM: x86: Introduce MSR filtering

2020-09-28T11:58:08+00:00

It's not desireable to have all MSRs always handled by KVM kernel space. Some
MSRs would be useful to handle in user space to either emulate behavior (like
uCode updates) or differentiate whether they are valid based on the CPU model.

To allow user space to specify which MSRs it wants to see handled by KVM,
this patch introduces a new ioctl to push filter rules with bitmaps into
KVM. Based on these bitmaps, KVM can then decide whether to reject MSR access.
With the addition of KVM_CAP_X86_USER_SPACE_MSR it can also deflect the
denied MSR events to user space to operate on.

If no filter is populated, MSR handling stays identical to before.

Signed-off-by: Alexander Graf 

Message-Id: <20200925143422.21718-8-graf@amazon.com>
Signed-off-by: Paolo Bonzini

KVM: x86: Allow deflecting unknown MSR accesses to user space

2020-09-28T11:58:04+00:00

MSRs are weird. Some of them are normal control registers, such as EFER.
Some however are registers that really are model specific, not very
interesting to virtualization workloads, and not performance critical.
Others again are really just windows into package configuration.

Out of these MSRs, only the first category is necessary to implement in
kernel space. Rarely accessed MSRs, MSRs that should be fine tunes against
certain CPU models and MSRs that contain information on the package level
are much better suited for user space to process. However, over time we have
accumulated a lot of MSRs that are not the first category, but still handled
by in-kernel KVM code.

This patch adds a generic interface to handle WRMSR and RDMSR from user
space. With this, any future MSR that is part of the latter categories can
be handled in user space.

Furthermore, it allows us to replace the existing "ignore_msrs" logic with
something that applies per-VM rather than on the full system. That way you
can run productive VMs in parallel to experimental ones where you don't care
about proper MSR handling.

Signed-off-by: Alexander Graf 
Reviewed-by: Jim Mattson 

Message-Id: <20200925143422.21718-3-graf@amazon.com>
Signed-off-by: Paolo Bonzini

KVM: MIPS: Change the definition of kvm type

2020-09-11T17:22:52+00:00

MIPS defines two kvm types:

 #define KVM_VM_MIPS_TE          0
 #define KVM_VM_MIPS_VZ          1

In Documentation/virt/kvm/api.rst it is said that "You probably want to
use 0 as machine type", which implies that type 0 be the "automatic" or
"default" type. And, in user-space libvirt use the null-machine (with
type 0) to detect the kvm capability, which returns "KVM not supported"
on a VZ platform.

I try to fix it in QEMU but it is ugly:
https://lists.nongnu.org/archive/html/qemu-devel/2020-08/msg05629.html

And Thomas Huth suggests me to change the definition of kvm type:
https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg03281.html

So I define like this:

 #define KVM_VM_MIPS_AUTO        0
 #define KVM_VM_MIPS_VZ          1
 #define KVM_VM_MIPS_TE          2

Since VZ and TE cannot co-exists, using type 0 on a TE platform will
still return success (so old user-space tools have no problems on new
kernels); the advantage is that using type 0 on a VZ platform will not
return failure. So, the only problem is "new user-space tools use type
2 on old kernels", but if we treat this as a kernel bug, we can backport
this patch to old stable kernels.

Signed-off-by: Huacai Chen 
Message-Id: <1599734031-28746-1-git-send-email-chenhc@lemote.com>
Signed-off-by: Paolo Bonzini

arm64/x86: KVM: Introduce steal-time cap

2020-08-21T13:05:19+00:00

arm64 requires a vcpu fd (KVM_HAS_DEVICE_ATTR vcpu ioctl) to probe
support for steal-time. However this is unnecessary, as only a KVM
fd is required, and it complicates userspace (userspace may prefer
delaying vcpu creation until after feature probing). Introduce a cap
that can be checked instead. While x86 can already probe steal-time
support with a kvm fd (KVM_GET_SUPPORTED_CPUID), we add the cap there
too for consistency.

Signed-off-by: Andrew Jones 
Signed-off-by: Marc Zyngier 
Reviewed-by: Steven Price 
Link: https://lore.kernel.org/r/20200804170604.42662-7-drjones@redhat.com

Merge tag 'kvm-s390-next-5.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into kvm-next-5.6

2020-08-03T18:19:13+00:00

KVM: s390: Enhancement for 5.9
- implement diagnose 318

KVM: x86: Add a capability for GUEST_MAXPHYADDR < HOST_MAXPHYADDR support

2020-07-10T21:01:53+00:00

This patch adds a new capability KVM_CAP_SMALLER_MAXPHYADDR which
allows userspace to query if the underlying architecture would
support GUEST_MAXPHYADDR < HOST_MAXPHYADDR and hence act accordingly
(e.g. qemu can decide if it should warn for -cpu ..,phys-bits=X)

The complications in this patch are due to unexpected (but documented)
behaviour we see with NPF vmexit handling in AMD processor.  If
SVM is modified to add guest physical address checks in the NPF
and guest #PF paths, we see the followning error multiple times in
the 'access' test in kvm-unit-tests:

            test pte.p pte.36 pde.p: FAIL: pte 2000021 expected 2000001
            Dump mapping: address: 0x123400000000
            ------L4: 24c3027
            ------L3: 24c4027
            ------L2: 24c5021
            ------L1: 1002000021

This is because the PTE's accessed bit is set by the CPU hardware before
the NPF vmexit. This is handled completely by hardware and cannot be fixed
in software.

Therefore, availability of the new capability depends on a boolean variable
allow_smaller_maxphyaddr which is set individually by VMX and SVM init
routines. On VMX it's always set to true, on SVM it's only set to true
when NPT is not enabled.

CC: Tom Lendacky 
CC: Babu Moger 
Signed-off-by: Mohammed Gamal 
Message-Id: <20200710154811.418214-10-mgamal@redhat.com>
Signed-off-by: Paolo Bonzini

kvm: x86: Add "last CPU" to some KVM_EXIT information

2020-07-08T20:21:45+00:00

More often than not, a failed VM-entry in an x86 production
environment is induced by a defective CPU. To help identify the bad
hardware, include the id of the last logical CPU to run a vCPU in the
information provided to userspace on a KVM exit for failed VM-entry or
for KVM internal errors not associated with emulation. The presence of
this additional information is indicated by a new capability,
KVM_CAP_LAST_CPU.

Signed-off-by: Jim Mattson 
Reviewed-by: Oliver Upton 
Reviewed-by: Peter Shier 
Message-Id: <20200603235623.245638-5-jmattson@google.com>
Signed-off-by: Paolo Bonzini

s390/kvm: diagnose 0x318 sync and reset

2020-06-23T08:55:33+00:00

DIAGNOSE 0x318 (diag318) sets information regarding the environment
the VM is running in (Linux, z/VM, etc) and is observed via
firmware/service events.

This is a privileged s390x instruction that must be intercepted by
SIE. Userspace handles the instruction as well as migration. Data
is communicated via VCPU register synchronization.

The Control Program Name Code (CPNC) is stored in the SIE block. The
CPNC along with the Control Program Version Code (CPVC) are stored
in the kvm_vcpu_arch struct.

This data is reset on load normal and clear resets.

Signed-off-by: Collin Walling 
Reviewed-by: Janosch Frank 
Acked-by: Cornelia Huck 
Reviewed-by: David Hildenbrand 
Link: https://lore.kernel.org/r/20200622154636.5499-3-walling@linux.ibm.com
[borntraeger@de.ibm.com: fix sync_reg position]
Signed-off-by: Christian Borntraeger

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2020-06-03T22:13:47+00:00

Pull kvm updates from Paolo Bonzini:
 "ARM:
   - Move the arch-specific code into arch/arm64/kvm

   - Start the post-32bit cleanup

   - Cherry-pick a few non-invasive pre-NV patches

  x86:
   - Rework of TLB flushing

   - Rework of event injection, especially with respect to nested
     virtualization

   - Nested AMD event injection facelift, building on the rework of
     generic code and fixing a lot of corner cases

   - Nested AMD live migration support

   - Optimization for TSC deadline MSR writes and IPIs

   - Various cleanups

   - Asynchronous page fault cleanups (from tglx, common topic branch
     with tip tree)

   - Interrupt-based delivery of asynchronous "page ready" events (host
     side)

   - Hyper-V MSRs and hypercalls for guest debugging

   - VMX preemption timer fixes

  s390:
   - Cleanups

  Generic:
   - switch vCPU thread wakeup from swait to rcuwait

  The other architectures, and the guest side of the asynchronous page
  fault work, will come next week"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (256 commits)
  KVM: selftests: fix rdtsc() for vmx_tsc_adjust_test
  KVM: check userspace_addr for all memslots
  KVM: selftests: update hyperv_cpuid with SynDBG tests
  x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls
  x86/kvm/hyper-v: enable hypercalls regardless of hypercall page
  x86/kvm/hyper-v: Add support for synthetic debugger interface
  x86/hyper-v: Add synthetic debugger definitions
  KVM: selftests: VMX preemption timer migration test
  KVM: nVMX: Fix VMX preemption timer migration
  x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit
  KVM: x86/pmu: Support full width counting
  KVM: x86/pmu: Tweak kvm_pmu_get_msr to pass 'struct msr_data' in
  KVM: x86: announce KVM_FEATURE_ASYNC_PF_INT
  KVM: x86: acknowledgment mechanism for async pf page ready notifications
  KVM: x86: interrupt based APF 'page ready' event delivery
  KVM: introduce kvm_read_guest_offset_cached()
  KVM: rename kvm_arch_can_inject_async_page_present() to kvm_arch_can_dequeue_async_page_present()
  KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info
  Revert "KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously"
  KVM: VMX: Replace zero-length array with flexible-array
  ...