History log of /freebsd-10.2-release/sys/amd64/vmm/intel/vmx_support.S
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# 285830 23-Jul-2015 gjb

- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

# 276386 30-Dec-2014 neel

MFC 261321
Rename the AMD MSR_PERFCTR[0-3] so the Pentium Pro MSR_PERFCTR[0-1] aren't
redefined.

MFC r273214
Fix build to not bogusly always rebuild vmm.ko.

MFC r273338
Add support for AMD's nested page tables in pmap.c:
- Provide the correct bit mask for various bit fields in a PTE (e.g. valid bit)
for a pmap of type PT_RVI.
- Add a function 'pmap_type_guest(pmap)' that returns TRUE if the pmap is of
type PT_EPT or PT_RVI.

Add CPU_SET_ATOMIC_ACQ(num, cpuset):
This is used when activating a vcpu in the nested pmap. Using the 'acquire'
variant guarantees that the load of the 'pm_eptgen' will happen only after
the vcpu is activated in 'pm_active'.

Add defines for various AMD-specific MSRs.

Discussed with: kib (r261321)


# 268953 21-Jul-2014 jhb

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.


# 266339 17-May-2014 jhb

MFC 259641,259863,259924,259937,259961,259978,260380,260383,260410,260466,
260531,260532,260550,260619,261170,261453,261621,263280,263290,264516:
Add support for local APIC hardware-assist.
- Restructure vlapic access and register handling to support hardware-assist
for the local APIC.
- Use the 'Virtual Interrupt Delivery' and 'Posted Interrupt Processing'
feature of Intel VT-x if supported by hardware.
- Add an API to rendezvous all active vcpus in a virtual machine and use
it to support level triggered interrupts with VT-x 'Virtual Interrupt
Delivery'.
- Use a cheaper IPI handler than IPI_AST for nested page table shootdowns
and avoid doing unnecessary nested TLB invalidations.

Reviewed by: neel


# 264619 17-Apr-2014 jhb

MFC 258860,260167,260238,260397:
- Restructure the VMX code to enter and exit the guest. In large part this
change hides the setjmp/longjmp semantics of VM enter/exit.
vmx_enter_guest() is used to enter guest context and vmx_exit_guest() is
used to transition back into host context.

Fix a longstanding race where a vcpu interrupt notification might be
ignored if it happens after vmx_inject_interrupts() but before host
interrupts are disabled in vmx_resume/vmx_launch. We now call
vmx_inject_interrupts() with host interrupts disabled to prevent this.
- The 'protection' field in the VM exit collateral for the PAGING exit is
not used - get rid of it.

Reviewed by: grehan


# 256281 10-Oct-2013 gjb

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation


# 256072 05-Oct-2013 neel

Merge projects/bhyve_npt_pmap into head.

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


# 245678 20-Jan-2013 neel

Add svn properties to the recently merged bhyve source files.

The pre-commit hook will not allow any commits without the svn:keywords
property in head.


# 245652 19-Jan-2013 neel

Merge projects/bhyve to head.

'bhyve' was developed by grehan@ and myself at NetApp (thanks!).

Special thanks to Peter Snyder, Joe Caradonna and Michael Dexter for their
support and encouragement.

Obtained from: NetApp


# 241921 23-Oct-2012 neel

Test for AST pending with interrupts disabled right before entering the guest.

If an IPI was delivered to this cpu before interrupts were disabled
then return right away via vmx_setjmp() with a return value of VMX_RETURN_AST.

Obtained from: NetApp


# 222112 20-May-2011 neel

Fix a long standing bug in VMXCTX_GUEST_RESTORE().

There was an assumption by the "callers" of this macro that on "return" the
%rsp will be pointing to the 'vmxctx'. The macro was not doing this and thus
when trying to restore host state on an error from "vmlaunch" or "vmresume"
we were treating the memory locations on the host stack as 'struct vmxctx'.
This led to all sorts of weird bugs like double faults or invalid instruction
faults.

This bug is exposed by the -O2 option used to compile the kernel module. With
the -O2 flag the compiler will optimize the following piece of code:

int loopstart = 1;
...
if (loopstart) {
loopstart = 0;
vmx_launch();
} else
vmx_resume();

into this:

vmx_launch();

Since vmx_launch() and vmx_resume() are declared to be __dead2 functions the
compiler is free to do this. The compiler has no way to know that the
functions return indirectly through vmx_setjmp(). This optimization in turn
leads us to trigger the bug in VMXCTX_GUEST_RESTORE().

With this change we can boot a 8.1 guest on a 9.0 host.

Reported by: jhb@


# 221914 14-May-2011 jhb

First cut at porting the kernel portions of 221828 and 221905 from the
BHyVe reference branch to HEAD.


# 221828 13-May-2011 grehan

Import of bhyve hypervisor and utilities, part 1.
vmm.ko - kernel module for VT-x, VT-d and hypervisor control
bhyve - user-space sequencer and i/o emulation
vmmctl - dump of hypervisor register state
libvmm - front-end to vmm.ko chardev interface

bhyve was designed and implemented by Neel Natu.

Thanks to the following folk from NetApp who helped to make this available:
Joe CaraDonna
Peter Snyder
Jeff Heller
Sandeep Mann
Steve Miller
Brian Pawlowski