KVM selftests changes for 7.3, part 2

 - Fix several issues with seeding KVM's pRNG, and rework the pRNG APIs to that
   the pRNG can be sanely used in host code, not just guest code.

 - Add an IRQ test to validate virtual IRQ deliverty for IRQs wired up via
   KVM_IRQFD + KVM_SET_GSI_ROUTING, with optional support for triggering IRQs
   via writes to an assigned VFIO device.

 - Add syscall wrappers to assert success on a variety of pthreads and CPU
   affinity APIs.

 - Set vCPU pthread affinity as early as possible to reduce contention issues
   that were surfaced by PREEMPT_LAZY, which result in runtimes of over a
   minute on large hosts, versus the expected ~5 seconds.

 - Rework the PMU counters test to run each testcase using a single VM with
   many vCPUs for each sub-testcase, instead of using a unique VM for each
   sub-testcase.  This cuts the runtime by ~20x.

KVM selftests changes for 7.3, part 1

 - Clean up nested SVM's handling of GPRs on L2<=>L1 transitions, reuse the
   functionality for nested VMX, and drop the ucall hack that was fudging
   around the lack of GPR switching on nVMX.

 - Add a stress test to verify KVM doesn't clobber/drop #PF state, e.g. CR2,
   across save/restore, including when L2 is active.

 - Add a test to verify KVM_CREATE_VM accepts exactly what is reported by
   KVM_CAP_VM_TYPES.

 - Misc selftests fixes and cleanups

LoongArch KVM changes for v7.3

1. Advertise already-supported capabilities.
2. Some bug fixes about timer and MMIO.
3. Some hardening about interrupt injection.
4. Replace kvm_err() with kvm_pr_unimpl().
5. Add FPU/LSX/LASX test cases for selftests.

Add LSX and LASX features when VM is created. These features are detected
firstly, enable it if it is available on host machine.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

To significantly reduce the PMU counter test's runtime, without sacrificing
test coverage in the aggregate, test a random GP counter in the arch events
testcase instead of testing every possible GP counter.  Testing every PMC
in every run of the test significantly increases the runtime of the test,
without providing an equivalent increase in validation coverage, as the
odds of a KVM having a bug that only affected a subset of counters and only
when testing all other counters are extremely low.

Opportunistically clean up kvm_random_u64_in_range() to eliminate
unnecessary newlines.

Link: https://patch.msgid.link/20260804210046.3413149-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Add and use KVM wrappers for pthread_{cancel,join}() so that selftests
don't need to manually assert that the syscalls succeeded.

Note, the vast majority tests don't actually assert success, but they all
obviously rely on the syscall to succeed.

Other than explicitly failing if a syscall fails, no functional change
intended.

Link: https://patch.msgid.link/20260731195612.2697986-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Add and use a KVM wrapper for pthread_create() syscall so that selftests
don't need to manually assert that the syscall succeeded.

Note, most tests don't actually assert success, but they all obviously
rely on the syscall to succeed.

Other than explicitly failing if pthread_create() fails, no functional
change intended.

Link: https://patch.msgid.link/20260731195612.2697986-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Extract kvm_pick_random_cpu() out of pin_task_to_random_cpu() so that tests
can choose a random CPU without having to immediately pin a task to that
CPU.

No functional change intended.

Link: https://patch.msgid.link/20260731195612.2697986-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

When pinning a task to a random CPU, return which CPU the task was pinned
to so that the caller can do things like avoid running other tasks on the
target CPU.

Link: https://patch.msgid.link/20260731195612.2697986-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

init_vmcs_control_fields() sets PFEC_MASK and PFEC_MATCH so that they
never match, which reverses the meaning of the PF_VECTOR bit in
EXCEPTION_BITMAP (which is zeroed), effectively enabling #PF
interception by default.

The relevant part of the SDM describes this:

  When a page fault occurs, a processor consults (1) bit 14 of the
  exception bitmap; (2) the error code produced with the page fault [PFEC];
  (3) the page-fault error-code mask field [PFEC_MASK]; and (4) the
  page-fault error-code match field [PFEC_MATCH].

  It checks if PFEC & PFEC_MASK = PFEC_MATCH.  If there is equality, the
  specification of bit 14 in the exception bitmap is followed (for example,
  a VM exit occurs if that bit is set). If there is inequality, the meaning
  of that bit is reversed (for example, a VM exit occurs if that bit is
  clear).

Clear PFEC_MATCH such that there is equality, and the #PF bit in the
exception bitmap is followed, so that #PFs are not intercepted by default,
same as every other exception.  This also allows tests to set the #PF bit
in the exception bitmap if they want to intercept #PFs, without having to
muck with the PFEC_{MASK,MATCH} fields.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260728174232.2423257-10-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>