Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

* Meson version update
* fix search path when configuring with --cpu
* support for measured SEV boot with -kernel (Dov)
* fix missing BQL locks (Emanuele)
* retrieve applesmc key from the host (Pedro)
* KVM PV feature documentation (Vitaly)

# gpg: Signature made Tue 05 Oct 2021 04:13:00 AM PDT
# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg:                issuer "pbonzini@redhat.com"
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]

* remotes/bonzini/tags/for-upstream:
  meson: show library versions in the summary
  target/xtensa: list cores in a text file
  hexagon: use env keyword argument to pass PYTHONPATH
  meson: switch minimum meson version to 0.58.2, minimum recommended to 0.59.2
  meson: bump submodule to 0.59.2
  migration: add missing qemu_mutex_lock_iothread in migration_completion
  migration: block-dirty-bitmap: add missing qemu_mutex_lock_iothread
  configure, meson: move CPU_CFLAGS out of QEMU_CFLAGS
  hw/misc: applesmc: use host osk as default on macs
  x86/sev: generate SEV kernel loader hashes in x86_load_linux
  sev/i386: Introduce sev_add_kernel_loader_hashes for measured linux boot
  i386: docs: Briefly describe KVM PV features

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 101 insertions, 0 deletions

diff --git a/docs/system/i386/kvm-pv.rst b/docs/system/i386/kvm-pv.rst
new file mode 100644
index 0000000000..1e5a9923ef
--- /dev/null
+++ b/docs/system/i386/kvm-pv.rst
@@ -0,0 +1,100 @@
+Paravirtualized KVM features
+============================
+
+Description
+-----------
+
+In some cases when implementing hardware interfaces in software is slow, ``KVM``
+implements its own paravirtualized interfaces.
+
+Setup
+-----
+
+Paravirtualized ``KVM`` features are represented as CPU flags. The following
+features are enabled by default for any CPU model when ``KVM`` acceleration is
+enabled:
+
+- ``kvmclock``
+- ``kvm-nopiodelay``
+- ``kvm-asyncpf``
+- ``kvm-steal-time``
+- ``kvm-pv-eoi``
+- ``kvmclock-stable-bit``
+
+``kvm-msi-ext-dest-id`` feature is enabled by default in x2apic mode with split
+irqchip (e.g. "-machine ...,kernel-irqchip=split -cpu ...,x2apic").
+
+Note: when CPU model ``host`` is used, QEMU passes through all supported
+paravirtualized ``KVM`` features to the guest.
+
+Existing features
+-----------------
+
+``kvmclock``
+  Expose a ``KVM`` specific paravirtualized clocksource to the guest. Supported
+  since Linux v2.6.26.
+
+``kvm-nopiodelay``
+  The guest doesn't need to perform delays on PIO operations. Supported since
+  Linux v2.6.26.
+
+``kvm-mmu``
+  This feature is deprecated.
+
+``kvm-asyncpf``
+  Enable asynchronous page fault mechanism. Supported since Linux v2.6.38.
+  Note: since Linux v5.10 the feature is deprecated and not enabled by ``KVM``.
+  Use ``kvm-asyncpf-int`` instead.
+
+``kvm-steal-time``
+  Enable stolen (when guest vCPU is not running) time accounting. Supported
+  since Linux v3.1.
+
+``kvm-pv-eoi``
+  Enable paravirtualized end-of-interrupt signaling. Supported since Linux
+  v3.10.
+
+``kvm-pv-unhalt``
+  Enable paravirtualized spinlocks support. Supported since Linux v3.12.
+
+``kvm-pv-tlb-flush``
+  Enable paravirtualized TLB flush mechanism. Supported since Linux v4.16.
+
+``kvm-pv-ipi``
+  Enable paravirtualized IPI mechanism. Supported since Linux v4.19.
+
+``kvm-poll-control``
+  Enable host-side polling on HLT control from the guest. Supported since Linux
+  v5.10.
+
+``kvm-pv-sched-yield``
+  Enable paravirtualized sched yield feature. Supported since Linux v5.10.
+
+``kvm-asyncpf-int``
+  Enable interrupt based asynchronous page fault mechanism. Supported since Linux
+  v5.10.
+
+``kvm-msi-ext-dest-id``
+  Support 'Extended Destination ID' for external interrupts. The feature allows
+  to use up to 32768 CPUs without IRQ remapping (but other limits may apply making
+  the number of supported vCPUs for a given configuration lower). Supported since
+  Linux v5.10.
+
+``kvmclock-stable-bit``
+  Tell the guest that guest visible TSC value can be fully trusted for kvmclock
+  computations and no warps are expected. Supported since Linux v2.6.35.
+
+Supplementary features
+----------------------
+
+``kvm-pv-enforce-cpuid``
+  Limit the supported paravirtualized feature set to the exposed features only.
+  Note, by default, ``KVM`` allows the guest to use all currently supported
+  paravirtualized features even when they were not announced in guest visible
+  CPUIDs. Supported since Linux v5.10.
+
+
+Useful links
+------------
+
+Please refer to Documentation/virt/kvm in Linux for additional details.
diff --git a/docs/system/target-i386.rst b/docs/system/target-i386.rst
index 6a86d63863..4daa53c35d 100644
--- a/docs/system/target-i386.rst
+++ b/docs/system/target-i386.rst
@@ -26,6 +26,7 @@ Architectural features
    :maxdepth: 1
 
    i386/cpu
+   i386/kvm-pv
    i386/sgx
 
 .. _pcsys_005freq: