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    • Suravee Suthikulpanit's avatar
      KVM: SVM: Allow AVIC support on system w/ physical APIC ID > 255 · 4a204f78
      Suravee Suthikulpanit authored 
      Expand KVM's mask for the AVIC host physical ID to the full 12 bits defined
by the architecture.  The number of bits consumed by hardware is model
specific, e.g. early CPUs ignored bits 11:8, but there is no way for KVM
to enumerate the "true" size.  So, KVM must allow using all bits, else it
risks rejecting completely legal x2APIC IDs on newer CPUs.

This means KVM relies on hardware to not assign x2APIC IDs that exceed the
"true" width of the field, but presumably hardware is smart enough to tie
the width to the max x2APIC ID.  KVM also relies on hardware to support at
least 8 bits, as the legacy xAPIC ID is writable by software.  But, those
assumptions are unavoidable due to the lack of any way to enumerate the
"true" width.

Cc: stable@vger.kernel.org
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Fixes: 44a95dae ("KVM: x86: Detect and Initialize AVIC support")
Signed-off-by: default avatarSuravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Message-Id: <20220211000851.185799-1-suravee.suthikulpanit@amd.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      4a204f78
    • Sean Christopherson's avatar
      KVM: selftests: Add test to populate a VM with the max possible guest mem · b58c55d5
      Sean Christopherson authored 
      Add a selftest that enables populating a VM with the maximum amount of
guest memory allowed by the underlying architecture.  Abuse KVM's
memslots by mapping a single host memory region into multiple memslots so
that the selftest doesn't require a system with terabytes of RAM.

Default to 512gb of guest memory, which isn't all that interesting, but
should work on all MMUs and doesn't take an exorbitant amount of memory
or time.  E.g. testing with ~64tb of guest memory takes the better part
of an hour, and requires 200gb of memory for KVM's page tables when using
4kb pages.

To inflicit maximum abuse on KVM' MMU, default to 4kb pages (or whatever
the not-hugepage size is) in the backing store (memfd).  Use memfd for
the host backing store to ensure that hugepages are guaranteed when
requested, and to give the user explicit control of the size of hugepage
being tested.

By default, spin up as many vCPUs as there are available to the selftest,
and distribute the work of dirtying each 4kb chunk of memory across all
vCPUs.  Dirtying guest memory forces KVM to populate its page tables, and
also forces KVM to write back accessed/dirty information to struct page
when the guest memory is freed.

On x86, perform two passes with a MMU context reset between each pass to
coerce KVM into dropping all references to the MMU root, e.g. to emulate
a vCPU dropping the last reference.  Perform both passes and all
rendezvous on all architectures in the hope that arm64 and s390x can gain
similar shenanigans in the future.

Measure and report the duration of each operation, which is helpful not
only to verify the test is working as intended, but also to easily
evaluate the performance differences different page sizes.

Provide command line options to limit the amount of guest memory, set the
size of each slot (i.e. of the host memory region), set the number of
vCPUs, and to enable usage of hugepages.
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20220226001546.360188-29-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      b58c55d5
    • Sean Christopherson's avatar
      KVM: selftests: Define cpu_relax() helpers for s390 and x86 · 17ae5ebc
      Sean Christopherson authored 
      Add cpu_relax() for s390 and x86 for use in arch-agnostic tests.  arm64
already defines its own version.
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20220226001546.360188-28-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      17ae5ebc
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