MFC r282209:
Emulate the 'bit test' instruction.

MFC r282259:
Re-implement RTC current time calculation to eliminate the possibility of
losing time.

MFC r282281:
Advertise the MTRR feature via CPUID and emulate the minimal set of MTRR MSRs.

MFC r282284:
When an instruction cannot be decoded just return to userspace so bhyve(8)
can dump the instruction bytes.

MFC r282287:
Don't require <sys/cpuset.h> to be always included before <machine/vmm.h>.

MFC r282296:
Emulate MSR_SYSCFG which is accessed by Linux on AMD cpus when MTRRs are
enabled.

MFC r282301:
Relax limits when transitioning a vector from the IRR to the ISR and also
when extinguishing it from the ISR in response to an EOI.

MFC r282335:
Advertise an additional memory BAR in the "dummy" device emulation.

MFC r282336:
Emulate machine check related MSRs to allow guest OSes like Windows to boot.

MFC r282351:
Don't advertise the Intel SMX capability to the guest.

MFC r282407:
Emulate the 'CMP r/m8, imm8' instruction.

MFC r282519:
Add macros for AMD-specific bits in MSR_EFER: LMSLE, FFXSR and TCE.

MFC r282520:
Emulate guest writes to EFER_MSR properly.

MFC r282558:
Deprecate the 3-way return values from vm_gla2gpa() and vm_copy_setup().

MFC r282571:
Check 'td_owepreempt' and yield the vcpu thread if it is set.

MFC r282595:
Allow byte reads of AHCI registers.

MFC r282784:
Handling indirect descriptors is a capability of the host and not one that
needs to be negotiated. Use the host capabilities field and not the negotiated
field when verifying that indirect descriptors are supported.

MFC r282788:
Allow configuration of the sector size advertised to the guest.

MFC r282865:
Set the subvendor field in config space to the vendor ID. This is required
by the Windows virtio drivers to correctly match a device.

MFC r282922:
Bump the size of the blockif scatter-gather list to 67.

MFC r283075:
Fix off-by-one in array index bounds check. bhyveload would allow you to
create 33 entries on an array that only has 32 slots

MFC r283168:
Temporarily revert r282922 which bumped the max descriptors.

MFC r283255:
Emulate the "CMP r/m, reg" instruction (opcode 39H).

MFC r283256:
Add an option "--get-vmcs-exit-inst-length" to display the instruction length
of the instruction that caused the VM-exit.

MFC r283264:
Change the header type of the emulated host-bridge from type 1 to type 0.

MFC r283293:
Don't rely on the 'VM-exit instruction length' field in the VMCS to always
have an accurate length on an EPT violation.

MFC r283299:
Remove bogus verification of instruction length after instruction decode.

MFC r283308:
Exceptions don't deliver an error code in real mode.

MFC r283657:
Fix non-deterministic delays when accessing a vcpu that was in "running" or
"sleeping" state.

MFC r283973:
Use tunable 'hw.vmm.svm.features' to disable specific SVM features even
though they might be available in hardware. Use tunable 'hw.vmm.svm.num_asids'
to limit the number of ASIDs used by the hypervisor.

MFC r284046:
Fix regression in 'verify_gla()' with the RIP-relative addressing mode.

MFC r284174:
Support guest writes to the TSC by enabling the "use TSC offsetting"
execution control.

MFC r279444:
Allow passthrough devices to be hinted.

MFC r279683:
When ICW1 is issued the edge sense circuit is reset which means that
following an initialization a low-to-high transistion is necesary to
generate an interrupt.

MFC r279925:
Add -p parameter to list PCI device to pass through to the guest.

MFC r281559:
Fix handling of BUS_PROBE_NOWILDCARD in 'device_probe_child()'.

MFC r280447:
When fetching an instruction in non-64bit mode, consider the value of the
code segment base address.

MFC r280725:
Move legacy interrupt allocation for virtio devices to common code.

MFC r280775:
Fix the RTC device model to operate correctly in 12-hour mode.

MFC r280929:
Fix "MOVS" instruction memory to MMIO emulation.

MFC r280968:
Display instruction bytes and %rip prior to aborting due to an instruction
emulation error.

MFC r281145:
Enhance the support for Group 1 Extended opcodes for CMP, AND, OR instructions.

MFC r281542:
Initialize 'error' before use (Coverity IDs 1249748, 1249747, 1249751, 1249749)

MFC r281561:
Prior to aborting due to an ioport error, it is always interesting to see what
the guest's %rip is.

MFC r281611:
If the number of guest vcpus is less than '1' then flag it as an error.

MFC r281612:
Prefer 'vcpu_should_yield()' over checking 'curthread->td_flags' directly.

MFC r281630:
Relax the check on which vectors can be delivered through the APIC. According
to the Intel SDM vectors 16 through 255 are allowed to be delivered via the
local APIC.

MFC r281879:
Missing break in switch case (Coverity ID 1292499)

MFC r281946:
Don't allow guest to modify readonly bits in the PCI config 'status' register.

MFC r281987:
STOS/STOSB/STOSW/STOSD/STOSQ instruction emulation.

MFC r282206:
Implement the century byte in the RTC.

MFC r281700:
Workaround bhyve virtual disks operation on top of GEOM providers.

GEOM does not support scatter/gather lists in its I/Os. Such requests
are cut in pieces by physio(), that may be problematic, if those pieces
are not multiple of provider's sector size. If such case is detected,
move the data through temporary sequential buffer.

MFC r280154:
Report that we may have write cache, and that we do support FLUSH.

MFC r280133: Increase S/G list size of 32 to 33 entries.

32 entries are not enough for the worst case of misaligned 128KB request,
that made FreeBSD to chunk large quests in odd pieces.

MFC r280044:
According to Linux and QEMU, s/n equal to buffer is not zero-terminated.

This makes same s/n reported for both virtio and AHCI drivers.

MFC r280037:
Rewrite virtio block device driver to work asynchronously and use the block
I/O interface.

Asynchronous operation, based on r280026 change, allows to not block virtual
CPU during I/O processing, that on slow/busy storage can take seconds.
Use of recently improved block I/O interface allows to process multiple
requests same time, that improves random I/O performance on wide storages.

Benchmarks of virtual disk, backed by ZVOL on RAID10 pool of 4 HDDs, show
~3.5 times random read performance improvements, while no degradation on
linear I/O. Guest CPU usage during test dropped from 100% to almost zero.

MFC r280026, r280041:
Modify virtqueue helpers added in r253440 to allow queuing.

Original virtqueue design allows queued and out-of-order processing, but
helpers added in r253440 suppose only direct blocking in-order one.
It could be fine for network, etc., but it is a huge limitation for storage
devices.

MFC r279658, r279673, r279675:
Implement cache flush for ahci-hd and for virtio-blk over device.

MFC r279651, r279652, r279657:
Add support for TOPOLOGY feature of virtio block device.

Passing through physical block size/offset from underlying storage allows
guest to manage proper data and I/O alignment to improve performance.

MFC r270326
Fix a recursive lock acquisition in vi_reset_dev().

MFC r270434
Return the spurious interrupt vector (IRQ7 or IRQ15) if the atpic cannot find
any unmasked pin with an interrupt asserted.

MFC r270436
Fix a bug in the emulation of CPUID leaf 0x4.

MFC r270437
Add "hw.vmm.topology.threads_per_core" and "hw.vmm.topology.cores_per_package"
tunables to modify the default cpu topology advertised by bhyve.

MFC r270855
Set the 'inst_length' to '0' early on before any error conditions are detected
in the emulation of the task switch. If any exceptions are triggered then the
guest %rip should point to instruction that caused the task switch as opposed
to the one after it.

MFC r270857
The "SUB" instruction used in getcc() actually does 'x -= y' so use the
proper constraint for 'x'. The "+r" constraint indicates that 'x' is an
input and output register operand.

While here generate code for different variants of getcc() using a macro
GETCC(sz) where 'sz' indicates the operand size.

Update the status bits in %rflags when emulating AND and OR opcodes.

MFC r271439
Initialize 'bc_rdonly' to the right value.

MFC r271451
Optimize the common case of injecting an interrupt into a vcpu after a HLT
by explicitly moving it out of the interrupt shadow.

MFC r271888
Restructure the MSR handling so it is entirely handled by processor-specific
code.

MFC r271890
MSR_KGSBASE is no longer saved and restored from the guest MSR save area. This
behavior was changed in r271888 so update the comment block to reflect this.

MFC r271891
Add some more KTR events to help debugging.

MFC r272197
mmap(2) requires either MAP_PRIVATE or MAP_SHARED for non-anonymous mappings.

MFC r272395
Get rid of code that dealt with the hardware not being able to save/restore
the PAT MSR on guest exit/entry. This workaround was done for a beta release
of VMware Fusion 5 but is no longer needed in later versions.

All Intel CPUs since Nehalem have supported saving and restoring MSR_PAT
in the VM exit and entry controls.

MFC r272670
Inject #UD into the guest when it executes either 'MONITOR' or 'MWAIT'.

MFC r272710
Implement the FLUSH operation in the virtio-block emulation.

MFC r272838
iasl(8) expects integer fields in data tables to be specified as hexadecimal
values. Therefore the bit width of the "PM Timer Block" was actually being
interpreted as 50-bits instead of the expected 32-bit.

This eliminates an error message emitted by a Linux 3.17 guest during boot:
"Invalid length for FADT/PmTimerBlock: 50, using default 32"

MFC r272839
Support Intel-specific MSRs that are accessed when booting up a linux in bhyve:
- MSR_PLATFORM_INFO
- MSR_TURBO_RATIO_LIMITx
- MSR_RAPL_POWER_UNIT

MFC r273108
Emulate "POP r/m". This is needed to boot OpenBSD/i386 MP kernel in bhyve.

MFC r273212
Support stopping and restarting the AHCI command list via toggling PxCMD.ST
from '1' to '0' and back. This allows the driver a chance to recover if
for instance a timeout occurred due to activity on the host.

MFC virtio-net changes.

Re-tested with NetBSD/amd64 5.2.2, 6.1.4 and 7-beta.

r271299:
Add a callback to be notified about negotiated features.

r271338:
Allow vtnet operation without merged rx buffers.

NetBSD's virtio-net implementation doesn't negotiate
the merged rx-buffers feature. To support this, check
to see if the feature was negotiated, and then adjust
the operation of the receive path accordingly by using
a larger iovec, and a smaller rx header.
In addition, ignore writes to the (read-only) status byte.

Approved by: re (glebius)
Obtained from: Vincenzo Maffione, Universita` di Pisa (r271299)

MFC 266424,266476,266524,266573,266595,266626,266627,266633,266641,266642,
266708,266724,266934,266935,268521:
Emulation of the "ins" and "outs" instructions.

Various fixes for translating guest linear addresses to guest physical
addresses.

MFC 264353,264509,264768,264770,264825,264846,264988,265114,265165,265365,
265941,265951,266390,266550,266910:
Various bhyve fixes:
- Don't save host's return address in 'struct vmxctx'.
- Permit non-32-bit accesses to local APIC registers.
- Factor out common ioport handler code.
- Use calloc() in favor of malloc + memset.
- Change the vlapic timer frequency to be in the ballpark of contemporary
hardware.
- Allow the guest to read the TSC via MSR 0x10.
- A VMCS is always inactive when it exits the vmx_run() loop. Remove
redundant code and the misleading comment that suggest otherwise.
- Ignore writes to microcode update MSR. This MSR is accessed by RHEL7
guest.
Add KTR tracepoints to annotate wrmsr and rdmsr VM exits.
- Provide an alias for the userboot console and name it 'comconsole'.
- Use EV_ADD to create an mevent and EV_ENABLE to enable it.
- abort(3) the process in response to a VMEXIT_ABORT.
- Don't include the guest memory segments in the bhyve(8) process core dump.
- Make the vmx asm code dtrace-fbt-friendly.
- Allow vmx_getdesc() and vmx_setdesc() to be called for a vcpu that is in
the VCPU_RUNNING state.
- Enable VMX in the IA32_FEATURE_CONTROL MSR if it not enabled and the MSR
isn't locked.

MFC 260239,261268,265058:
Expand the support for PCI INTx interrupts including providing interrupt
routing information for INTx interrupts to I/O APIC pins and enabling
INTx interrupts in the virtio and AHCI backends.

MFC r256926, r257005

r256926
Fix AHCI ATAPI emulation when backed with /dev/cd0

- remove assumption that the backing file/device had
512-byte sectors
- fix incorrect iovec size variable that would result
in a buffer overrun when an o/s issued an i/o request
with more s/g elements than the blockif api

r257005
Export the block size capability to guests.
- Use #defines for capability bits
- Export the VTBLK_F_BLK_SIZE capability
- Fix bug in calculating capacity: it is in
512-byte units, not the underlying sector size

This allows virtio-blk to have backing devices
with non 512-byte sector sizes e.g. /dev/cd0, and
4K-block harddrives.

Approved by: re (glebius)

MFC r256709:

Eliminate unconditional debug printfs.

Linux writes to these nominally read-only registers,
so avoid having bhyve write warning messages to stdout
when the reg writes can be safely ignored. Change the
WPRINTF to DPRINTF which is conditional.

Approved by: re (delphij)

MFC r256389

Implement the virtio block 'get-ident' operation. This eliminates the
annoying verbose boot error of the form

g_handleattr: vtbd0 bio_length 24 len 28 -> EFAULT

The ident returned by bhyve is a text string 'BHYVE-XXXX-XXXX', where
the X's are the first bytes of the md5 hash of the backing filename.

Approved by: re (gjb)

MFC r282209:
Emulate the 'bit test' instruction.

MFC r282259:
Re-implement RTC current time calculation to eliminate the possibility of
losing time.

MFC r282281:
Advertise the MTRR feature via CPUID and emulate the minimal set of MTRR MSRs.

MFC r282284:
When an instruction cannot be decoded just return to userspace so bhyve(8)
can dump the instruction bytes.

MFC r282287:
Don't require <sys/cpuset.h> to be always included before <machine/vmm.h>.

MFC r282296:
Emulate MSR_SYSCFG which is accessed by Linux on AMD cpus when MTRRs are
enabled.

MFC r282301:
Relax limits when transitioning a vector from the IRR to the ISR and also
when extinguishing it from the ISR in response to an EOI.

MFC r282335:
Advertise an additional memory BAR in the "dummy" device emulation.

MFC r282336:
Emulate machine check related MSRs to allow guest OSes like Windows to boot.

MFC r282351:
Don't advertise the Intel SMX capability to the guest.

MFC r282407:
Emulate the 'CMP r/m8, imm8' instruction.

MFC r282519:
Add macros for AMD-specific bits in MSR_EFER: LMSLE, FFXSR and TCE.

MFC r282520:
Emulate guest writes to EFER_MSR properly.

MFC r282558:
Deprecate the 3-way return values from vm_gla2gpa() and vm_copy_setup().

MFC r282571:
Check 'td_owepreempt' and yield the vcpu thread if it is set.

MFC r282595:
Allow byte reads of AHCI registers.

MFC r282784:
Handling indirect descriptors is a capability of the host and not one that
needs to be negotiated. Use the host capabilities field and not the negotiated
field when verifying that indirect descriptors are supported.

MFC r282788:
Allow configuration of the sector size advertised to the guest.

MFC r282865:
Set the subvendor field in config space to the vendor ID. This is required
by the Windows virtio drivers to correctly match a device.

MFC r282922:
Bump the size of the blockif scatter-gather list to 67.

MFC r283075:
Fix off-by-one in array index bounds check. bhyveload would allow you to
create 33 entries on an array that only has 32 slots

MFC r283168:
Temporarily revert r282922 which bumped the max descriptors.

MFC r283255:
Emulate the "CMP r/m, reg" instruction (opcode 39H).

MFC r283256:
Add an option "--get-vmcs-exit-inst-length" to display the instruction length
of the instruction that caused the VM-exit.

MFC r283264:
Change the header type of the emulated host-bridge from type 1 to type 0.

MFC r283293:
Don't rely on the 'VM-exit instruction length' field in the VMCS to always
have an accurate length on an EPT violation.

MFC r283299:
Remove bogus verification of instruction length after instruction decode.

MFC r283308:
Exceptions don't deliver an error code in real mode.

MFC r283657:
Fix non-deterministic delays when accessing a vcpu that was in "running" or
"sleeping" state.

MFC r283973:
Use tunable 'hw.vmm.svm.features' to disable specific SVM features even
though they might be available in hardware. Use tunable 'hw.vmm.svm.num_asids'
to limit the number of ASIDs used by the hypervisor.

MFC r284046:
Fix regression in 'verify_gla()' with the RIP-relative addressing mode.

MFC r284174:
Support guest writes to the TSC by enabling the "use TSC offsetting"
execution control.

MFC r279444:
Allow passthrough devices to be hinted.

MFC r279683:
When ICW1 is issued the edge sense circuit is reset which means that
following an initialization a low-to-high transistion is necesary to
generate an interrupt.

MFC r279925:
Add -p parameter to list PCI device to pass through to the guest.

MFC r281559:
Fix handling of BUS_PROBE_NOWILDCARD in 'device_probe_child()'.

MFC r280447:
When fetching an instruction in non-64bit mode, consider the value of the
code segment base address.

MFC r280725:
Move legacy interrupt allocation for virtio devices to common code.

MFC r280775:
Fix the RTC device model to operate correctly in 12-hour mode.

MFC r280929:
Fix "MOVS" instruction memory to MMIO emulation.

MFC r280968:
Display instruction bytes and %rip prior to aborting due to an instruction
emulation error.

MFC r281145:
Enhance the support for Group 1 Extended opcodes for CMP, AND, OR instructions.

MFC r281542:
Initialize 'error' before use (Coverity IDs 1249748, 1249747, 1249751, 1249749)

MFC r281561:
Prior to aborting due to an ioport error, it is always interesting to see what
the guest's %rip is.

MFC r281611:
If the number of guest vcpus is less than '1' then flag it as an error.

MFC r281612:
Prefer 'vcpu_should_yield()' over checking 'curthread->td_flags' directly.

MFC r281630:
Relax the check on which vectors can be delivered through the APIC. According
to the Intel SDM vectors 16 through 255 are allowed to be delivered via the
local APIC.

MFC r281879:
Missing break in switch case (Coverity ID 1292499)

MFC r281946:
Don't allow guest to modify readonly bits in the PCI config 'status' register.

MFC r281987:
STOS/STOSB/STOSW/STOSD/STOSQ instruction emulation.

MFC r282206:
Implement the century byte in the RTC.

MFC r281700:
Workaround bhyve virtual disks operation on top of GEOM providers.

GEOM does not support scatter/gather lists in its I/Os. Such requests
are cut in pieces by physio(), that may be problematic, if those pieces
are not multiple of provider's sector size. If such case is detected,
move the data through temporary sequential buffer.

MFC r280154:
Report that we may have write cache, and that we do support FLUSH.

MFC r280133: Increase S/G list size of 32 to 33 entries.

32 entries are not enough for the worst case of misaligned 128KB request,
that made FreeBSD to chunk large quests in odd pieces.

MFC r280044:
According to Linux and QEMU, s/n equal to buffer is not zero-terminated.

This makes same s/n reported for both virtio and AHCI drivers.

MFC r280037:
Rewrite virtio block device driver to work asynchronously and use the block
I/O interface.

Asynchronous operation, based on r280026 change, allows to not block virtual
CPU during I/O processing, that on slow/busy storage can take seconds.
Use of recently improved block I/O interface allows to process multiple
requests same time, that improves random I/O performance on wide storages.

Benchmarks of virtual disk, backed by ZVOL on RAID10 pool of 4 HDDs, show
~3.5 times random read performance improvements, while no degradation on
linear I/O. Guest CPU usage during test dropped from 100% to almost zero.

MFC r280026, r280041:
Modify virtqueue helpers added in r253440 to allow queuing.

Original virtqueue design allows queued and out-of-order processing, but
helpers added in r253440 suppose only direct blocking in-order one.
It could be fine for network, etc., but it is a huge limitation for storage
devices.

MFC r279658, r279673, r279675:
Implement cache flush for ahci-hd and for virtio-blk over device.

MFC r279651, r279652, r279657:
Add support for TOPOLOGY feature of virtio block device.

Passing through physical block size/offset from underlying storage allows
guest to manage proper data and I/O alignment to improve performance.

MFC r270326
Fix a recursive lock acquisition in vi_reset_dev().

MFC r270434
Return the spurious interrupt vector (IRQ7 or IRQ15) if the atpic cannot find
any unmasked pin with an interrupt asserted.

MFC r270436
Fix a bug in the emulation of CPUID leaf 0x4.

MFC r270437
Add "hw.vmm.topology.threads_per_core" and "hw.vmm.topology.cores_per_package"
tunables to modify the default cpu topology advertised by bhyve.

MFC r270855
Set the 'inst_length' to '0' early on before any error conditions are detected
in the emulation of the task switch. If any exceptions are triggered then the
guest %rip should point to instruction that caused the task switch as opposed
to the one after it.

MFC r270857
The "SUB" instruction used in getcc() actually does 'x -= y' so use the
proper constraint for 'x'. The "+r" constraint indicates that 'x' is an
input and output register operand.

While here generate code for different variants of getcc() using a macro
GETCC(sz) where 'sz' indicates the operand size.

Update the status bits in %rflags when emulating AND and OR opcodes.

MFC r271439
Initialize 'bc_rdonly' to the right value.

MFC r271451
Optimize the common case of injecting an interrupt into a vcpu after a HLT
by explicitly moving it out of the interrupt shadow.

MFC r271888
Restructure the MSR handling so it is entirely handled by processor-specific
code.

MFC r271890
MSR_KGSBASE is no longer saved and restored from the guest MSR save area. This
behavior was changed in r271888 so update the comment block to reflect this.

MFC r271891
Add some more KTR events to help debugging.

MFC r272197
mmap(2) requires either MAP_PRIVATE or MAP_SHARED for non-anonymous mappings.

MFC r272395
Get rid of code that dealt with the hardware not being able to save/restore
the PAT MSR on guest exit/entry. This workaround was done for a beta release
of VMware Fusion 5 but is no longer needed in later versions.

All Intel CPUs since Nehalem have supported saving and restoring MSR_PAT
in the VM exit and entry controls.

MFC r272670
Inject #UD into the guest when it executes either 'MONITOR' or 'MWAIT'.

MFC r272710
Implement the FLUSH operation in the virtio-block emulation.

MFC r272838
iasl(8) expects integer fields in data tables to be specified as hexadecimal
values. Therefore the bit width of the "PM Timer Block" was actually being
interpreted as 50-bits instead of the expected 32-bit.

This eliminates an error message emitted by a Linux 3.17 guest during boot:
"Invalid length for FADT/PmTimerBlock: 50, using default 32"

MFC r272839
Support Intel-specific MSRs that are accessed when booting up a linux in bhyve:
- MSR_PLATFORM_INFO
- MSR_TURBO_RATIO_LIMITx
- MSR_RAPL_POWER_UNIT

MFC r273108
Emulate "POP r/m". This is needed to boot OpenBSD/i386 MP kernel in bhyve.

MFC r273212
Support stopping and restarting the AHCI command list via toggling PxCMD.ST
from '1' to '0' and back. This allows the driver a chance to recover if
for instance a timeout occurred due to activity on the host.

MFC virtio-net changes.

Re-tested with NetBSD/amd64 5.2.2, 6.1.4 and 7-beta.

r271299:
Add a callback to be notified about negotiated features.

r271338:
Allow vtnet operation without merged rx buffers.

NetBSD's virtio-net implementation doesn't negotiate
the merged rx-buffers feature. To support this, check
to see if the feature was negotiated, and then adjust
the operation of the receive path accordingly by using
a larger iovec, and a smaller rx header.
In addition, ignore writes to the (read-only) status byte.

Approved by: re (glebius)
Obtained from: Vincenzo Maffione, Universita` di Pisa (r271299)

MFC 266424,266476,266524,266573,266595,266626,266627,266633,266641,266642,
266708,266724,266934,266935,268521:
Emulation of the "ins" and "outs" instructions.

Various fixes for translating guest linear addresses to guest physical
addresses.

MFC 264353,264509,264768,264770,264825,264846,264988,265114,265165,265365,
265941,265951,266390,266550,266910:
Various bhyve fixes:
- Don't save host's return address in 'struct vmxctx'.
- Permit non-32-bit accesses to local APIC registers.
- Factor out common ioport handler code.
- Use calloc() in favor of malloc + memset.
- Change the vlapic timer frequency to be in the ballpark of contemporary
hardware.
- Allow the guest to read the TSC via MSR 0x10.
- A VMCS is always inactive when it exits the vmx_run() loop. Remove
redundant code and the misleading comment that suggest otherwise.
- Ignore writes to microcode update MSR. This MSR is accessed by RHEL7
guest.
Add KTR tracepoints to annotate wrmsr and rdmsr VM exits.
- Provide an alias for the userboot console and name it 'comconsole'.
- Use EV_ADD to create an mevent and EV_ENABLE to enable it.
- abort(3) the process in response to a VMEXIT_ABORT.
- Don't include the guest memory segments in the bhyve(8) process core dump.
- Make the vmx asm code dtrace-fbt-friendly.
- Allow vmx_getdesc() and vmx_setdesc() to be called for a vcpu that is in
the VCPU_RUNNING state.
- Enable VMX in the IA32_FEATURE_CONTROL MSR if it not enabled and the MSR
isn't locked.

MFC 260239,261268,265058:
Expand the support for PCI INTx interrupts including providing interrupt
routing information for INTx interrupts to I/O APIC pins and enabling
INTx interrupts in the virtio and AHCI backends.

MFC r256926, r257005

r256926
Fix AHCI ATAPI emulation when backed with /dev/cd0

- remove assumption that the backing file/device had
512-byte sectors
- fix incorrect iovec size variable that would result
in a buffer overrun when an o/s issued an i/o request
with more s/g elements than the blockif api

r257005
Export the block size capability to guests.
- Use #defines for capability bits
- Export the VTBLK_F_BLK_SIZE capability
- Fix bug in calculating capacity: it is in
512-byte units, not the underlying sector size

This allows virtio-blk to have backing devices
with non 512-byte sector sizes e.g. /dev/cd0, and
4K-block harddrives.

Approved by: re (glebius)

MFC r256709:

Eliminate unconditional debug printfs.

Linux writes to these nominally read-only registers,
so avoid having bhyve write warning messages to stdout
when the reg writes can be safely ignored. Change the
WPRINTF to DPRINTF which is conditional.

Approved by: re (delphij)

MFC r256389

Implement the virtio block 'get-ident' operation. This eliminates the
annoying verbose boot error of the form

g_handleattr: vtbd0 bio_length 24 len 28 -> EFAULT

The ident returned by bhyve is a text string 'BHYVE-XXXX-XXXX', where
the X's are the first bytes of the md5 hash of the backing filename.

Approved by: re (gjb)