Make the amd64/pmap code aware of nested page table mappings used by bhyve
guests. This allows bhyve to associate each guest with its own vmspace and
deal with nested page faults in the context of that vmspace. This also
enables features like accessed/dirty bit tracking, swapping to disk and
transparent superpage promotions of guest memory.
Guest vmspace:
Each bhyve guest has a unique vmspace to represent the physical memory
allocated to the guest. Each memory segment allocated by the guest is
mapped into the guest's address space via the 'vmspace->vm_map' and is
backed by an object of type OBJT_DEFAULT.
pmap types:
The amd64/pmap now understands two types of pmaps: PT_X86 and PT_EPT.
The PT_X86 pmap type is used by the vmspace associated with the host kernel
as well as user processes executing on the host. The PT_EPT pmap is used by
the vmspace associated with a bhyve guest.
Page Table Entries:
The EPT page table entries as mostly similar in functionality to regular
page table entries although there are some differences in terms of what
bits are used to express that functionality. For e.g. the dirty bit is
represented by bit 9 in the nested PTE as opposed to bit 6 in the regular
x86 PTE. Therefore the bitmask representing the dirty bit is now computed
at runtime based on the type of the pmap. Thus PG_M that was previously a
macro now becomes a local variable that is initialized at runtime using
'pmap_modified_bit(pmap)'.
An additional wrinkle associated with EPT mappings is that older Intel
processors don't have hardware support for tracking accessed/dirty bits in
the PTE. This means that the amd64/pmap code needs to emulate these bits to
provide proper accounting to the VM subsystem. This is achieved by using
the following mapping for EPT entries that need emulation of A/D bits:
Bit Position Interpreted By
PG_V 52 software (accessed bit emulation handler)
PG_RW 53 software (dirty bit emulation handler)
PG_A 0 hardware (aka EPT_PG_RD)
PG_M 1 hardware (aka EPT_PG_WR)
The idea to use the mapping listed above for A/D bit emulation came from
Alan Cox (alc@).
The final difference with respect to x86 PTEs is that some EPT implementations
do not support superpage mappings. This is recorded in the 'pm_flags' field
of the pmap.
TLB invalidation:
The amd64/pmap code has a number of ways to do invalidation of mappings
that may be cached in the TLB: single page, multiple pages in a range or the
entire TLB. All of these funnel into a single EPT invalidation routine called
'pmap_invalidate_ept()'. This routine bumps up the EPT generation number and
sends an IPI to the host cpus that are executing the guest's vcpus. On a
subsequent entry into the guest it will detect that the EPT has changed and
invalidate the mappings from the TLB.
Guest memory access:
Since the guest memory is no longer wired we need to hold the host physical
page that backs the guest physical page before we can access it. The helper
functions 'vm_gpa_hold()/vm_gpa_release()' are available for this purpose.
PCI passthru:
Guest's with PCI passthru devices will wire the entire guest physical address
space. The MMIO BAR associated with the passthru device is backed by a
vm_object of type OBJT_SG. An IOMMU domain is created only for guest's that
have one or more PCI passthru devices attached to them.
Limitations:
There isn't a way to map a guest physical page without execute permissions.
This is because the amd64/pmap code interprets the guest physical mappings as
user mappings since they are numerically below VM_MAXUSER_ADDRESS. Since PG_U
shares the same bit position as EPT_PG_EXECUTE all guest mappings become
automatically executable.
Thanks to Alan Cox and Konstantin Belousov for their rigorous code reviews
as well as their support and encouragement.
Thanks for John Baldwin for reviewing the use of OBJT_SG as the backing
object for pci passthru mmio regions.
Special thanks to Peter Holm for testing the patch on short notice.
Approved by: re
Discussed with: grehan
Reviewed by: alc, kib
Tested by: pho
immediate operand. The presence of an SIB byte in decoding the ModR/M field
would cause 'imm_bytes' to not be set to the correct value.
Fix this by initializing 'imm_bytes' independent of the ModR/M decoding.
Reported by: grehan@
Approved by: re@
the maximum number of VT-d domains (256 on a Sandybridge). We now allocate a
VT-d domain for a guest only if the administrator has explicitly configured
one or more PCI passthru device(s).
If there are no PCI passthru devices configured (the common case) then the
number of virtual machines is no longer limited by the maximum number of
VT-d domains.
Reviewed by: grehan@
Approved by: re@
This is a workaround to hide the fact that we do not have any code to
demote a superpage mapping before we unmap a single page that is part
of the superpage.
architectural state on CR vmexits by guaranteeing
that EFER, CR0 and the VMCS entry controls are
all in sync when transitioning to IA-32e mode.
Submitted by: Tycho Nightingale (tycho.nightingale <at> plurisbusnetworks.com)
of unloading the module while VMs existed. This would
result in EBUSY, but would prevent further operations
on VMs resulting in the module being impossible to
unload.
Submitted by: Tycho Nightingale (tycho.nightingale <at> plurisbusnetworks.com)
Reviewed by: grehan, neel
This was exposed with AP spinup of Linux, and
booting OpenBSD, where the CR0 register is unconditionally
written to prior to the longjump to enter protected
mode. The CR-vmexit handling was not updating CPU state which
resulted in a vmentry failure with invalid guest state.
A follow-on submit will fix the CPU state issue, but this
fix prevents the CR-vmexit prior to entering protected
mode by properly initializing and maintaining CR* state.
Reviewed by: neel
Reported by: Gopakumar.T @ netapp
bhyve process when an unhandled one is encountered.
Hide some additional capabilities from the guest (e.g. debug store).
This fixes the issue with FreeBSD 9.1 MP guests exiting the VM on
AP spinup (where CPUID is used when sync'ing the TSCs) and the
issue with the Java build where CPUIDs are issued from a guest
userspace.
Submitted by: tycho nightingale at pluribusnetworks com
Reviewed by: neel
Reported by: many
An array-type stat in vmm.ko is defined as follows:
VMM_STAT_ARRAY(IPIS_SENT, VM_MAXCPU, "ipis sent to vcpu");
It is incremented as follows:
vmm_stat_array_incr(vm, vcpuid, IPIS_SENT, array_index, 1);
And output of 'bhyvectl --get-stats' looks like:
ipis sent to vcpu[0] 3114
ipis sent to vcpu[1] 0
Reviewed by: grehan
Obtained from: NetApp
The initial version of this came from Sandvine but had "PROVIDED BY NETAPP,
INC" in the copyright text, presuambly because the license block was copied
from another file. Replace it with standard "AUTHOR AND CONTRIBUTORS" form.
Approvided by: grehan@
Rework the guest register fetch code to allow the RIP to
be extracted from the VMCS while the kernel decoder is
functioning.
Hit by the OpenBSD local-apic code.
Submitted by: neel
Reviewed by: grehan
Obtained from: NetApp
- use clock_gettime(2) as the time base for the emulated ACPI timer instead
of directly using rdtsc().
- don't advertise the invariant TSC capability to the guest to discourage it
from using the TSC as its time base.
Discussed with: jhb@ (about making 'smp_tsc' a global)
Reported by: Dan Mack on freebsd-virtualization@
Obtained from: NetApp
decode. This is to accomodate hardware assist implementations that do not
provide the 'guest linear address' as part of nested page fault collateral.
Submitted by: Anish Gupta (akgupt3 at gmail dot com)
This can be done by using the new macros VMM_STAT_INTEL() and VMM_STAT_AMD().
Statistic counters that are common across the two are defined using VMM_STAT().
Suggested by: Anish Gupta
Discussed with: grehan
Obtained from: NetApp
Prior to this change pinning was implemented via an ioctl (VM_SET_PINNING)
that called 'sched_bind()' on behalf of the user thread.
The ULE implementation of 'sched_bind()' bumps up 'td_pinned' which in turn
runs afoul of the assertion '(td_pinned == 0)' in userret().
Using the cpuset affinity to implement pinning of the vcpu threads works with
both 4BSD and ULE schedulers and has the happy side-effect of getting rid
of a bunch of code in vmm.ko.
Discussed with: grehan
can only be located at the beginning or the end of the BAR.
If the MSI-table is located in the middle of a BAR then we will split the
BAR into two and create two mappings - one before the table and one after
the table - leaving a hole in place of the table so accesses to it can be
trapped and emulated.
Obtained from: NetApp
The maximum length of an environment variable puts a limitation on the
number of passthru devices that can be specified via a single variable.
The workaround is to allow user to specify passthru devices via multiple
environment variables instead of a single one.
Obtained from: NetApp
that 'smp_started != 0'.
This is required because the VT-x initialization calls smp_rendezvous()
to set the CR4_VMXE bit on all the cpus.
With this change we can preload vmm.ko from the loader.
Reported by: alfred@, sbruno@
Obtained from: NetApp
x2apic mode on the guest.
The guest can decide whether or not it wants to use legacy mmio or x2apic
access to the APIC by writing to the MSR_APICBASE register.
Obtained from: NetApp
by clang in the local APIC code.
0x81 is a read-modify-write instruction - the EPT check
that only allowed read or write and not both has been
relaxed to allow read and write.
Reviewed by: neel
Obtained from: NetApp
On a nested page table fault the hypervisor will:
- fetch the instruction using the guest %rip and %cr3
- decode the instruction in 'struct vie'
- emulate the instruction in host kernel context for local apic accesses
- any other type of mmio access is punted up to user-space (e.g. ioapic)
The decoded instruction is passed as collateral to the user-space process
that is handling the PAGING exit.
The emulation code is fleshed out to include more addressing modes (e.g. SIB)
and more types of operands (e.g. imm8). The source code is unified into a
single file (vmm_instruction_emul.c) that is compiled into vmm.ko as well
as /usr/sbin/bhyve.
Reviewed by: grehan
Obtained from: NetApp
