Some older compilers, when generating PIC code, cannot handle inline
asm that clobbers %ebx (because %ebx is used as the GOT offset
register). Userspace versions avoid clobbering %ebx by saving it to
stack before executing the CPUID instruction.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
On CPUs supporting cmpxchg8b, fetch is performed by cmpxchg8b on
corresponding CPU slot, which unconditionally write to the slot. If
for that slot, the owner CPU increments it, then both CPUs might run
the cmpxchg8b instruction concurrently and this might race and
override the incremental write. So the counter update would be lost.
Fix it by implementing fetch as IPI and accumulation of result. It is
acceptable for rare counter64 fetch operation to be more expensive.
Diagnosed and tested by: Andreas Longwitz <longwitz@incore.de>
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Effectively all i386 kernels now have two pmaps compiled in: one
managing PAE pagetables, and another non-PAE. The implementation is
selected at cold time depending on the CPU features. The vm_paddr_t is
always 64bit now. As result, nx bit can be used on all capable CPUs.
Option PAE only affects the bus_addr_t: it is still 32bit for non-PAE
configs, for drivers compatibility. Kernel layout, esp. max kernel
address, low memory PDEs and max user address (same as trampoline
start) are now same for PAE and for non-PAE regardless of the type of
page tables used.
Non-PAE kernel (when using PAE pagetables) can handle physical memory
up to 24G now, larger memory requires re-tuning the KVA consumers and
instead the code caps the maximum at 24G. Unfortunately, a lot of
drivers do not use busdma(9) properly so by default even 4G barrier is
not easy. There are two tunables added: hw.above4g_allow and
hw.above24g_allow, the first one is kept enabled for now to evaluate
the status on HEAD, second is only for dev use.
i386 now creates three freelists if there is any memory above 4G, to
allow proper bounce pages allocation. Also, VM_KMEM_SIZE_SCALE changed
from 3 to 1.
The PAE_TABLES kernel config option is retired.
In collaboarion with: pho
Discussed with: emaste
Reviewed by: markj
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D18894
It seems that libkern/mcount.c is the only consumer of vm/pmap.h that
does not include machine/atomic.h. Make it work by bringing
machine/atomic.h when pmap.h is used for kernel non-asm .c file.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
pmap_kextract().
pmap_kextract() can race with promotion/demotion on the kernel page
table, in which case current non-atomic 64bit read would see torn
value, breaking pmap_kextract(). pmap_kextract() would correctly
handle either promoted or demoted PDE, but not a mix where one word
is from a different state.
It requires PAE and > 4G memory to reproduce. We observed this in
real loads, both for intensive use of malloc(9)/free(9) where
vtoslab() returned invalid pointer to the slab, and with the use of
busdma_bounce, where incorrect page was bounced.
In collaboration with: pho
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D18714
Avoid using DELAY() since it can try to use spin locks on CPUs without
a P-state invariant TSC. For cpu_lock_delay(), always use the TSC if
it exists (even if it is not P-state invariant) to delay for a
microsecond. If the TSC does not exist, read from I/O port 0x84 to
delay instead.
PR: 228768
Reported by: Roger Hammerstein <cheeky.m@live.com>
Reviewed by: kib
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D17851
Replace a call to DELAY(1) with a new cpu_lock_delay() KPI. Currently
cpu_lock_delay() is defined to DELAY(1) on all platforms. However,
platforms with a DELAY() implementation that uses spin locks should
implement a custom cpu_lock_delay() doesn't use locks.
Reviewed by: kib
MFC after: 3 days
This simplifies the runtime logic and reduces the number of
runtime-constant branches.
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
Approved by: re (gjb)
Differential revision: https://reviews.freebsd.org/D16736
Add pmap_activate_boot() for i386, move the invocation on APs from MD
init_secondary() to x86 init_secondary_tail().
Suggested by: alc
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
Approved by: re (marius)
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D16893
The support for lazy pmap invalidations on i386 was removed in r281707.
This removes the constant for the IPI and stops accounting for it when
sizing the interrupt count arrays.
Reviewed by: kib
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D16801
There's no differene between VM_FREELIST_ISADMA and VM_FREELIST_LOWMEM
except for the default boundary (16MB on x86 and 256MB on MIPS, but
they are otherwise the same). We don't need both for any system we
support (there were some really old ARC systems that did have ISA/EISA
bus, but we never ran on them and they are too old to ever grow
support for).
Differential Review: https://reviews.freebsd.org/D16290
Without this, the support for transparent superpage promotion on i386
was left disabled.
Reviewed by: alc, kib
Differential Revision: https://reviews.freebsd.org/D16279
add support for explicitly requesting that pmap_enter() create a 2 or 4 MB
page mapping. (Essentially, this feature allows the machine-independent
layer to create superpage mappings preemptively, and not wait for automatic
promotion to occur.)
Export pmap_ps_enabled() to the machine-independent layer.
Add a flag to pmap_pv_insert_pde() that specifies whether it should fail or
reclaim a PV entry when one is not available.
Refactor pmap_enter_pde() into two functions, one by the same name, that is
a general-purpose function for creating PDE PG_PS mappings, and another,
pmap_enter_4mpage(), that is used to prefault 2 or 4 MB read- and/or
execute-only mappings for execve(2), mmap(2), and shmat(2).
Reviewed by: kib
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D16246
This restores counters(9) operation.
Revert r336024. Improve assert of pcpu size on x86.
Reviewed by: mmacy
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D16163
Due to the way rtld creates mappings for the shared objects, each dso
causes unmap of at least three guard map entries. For instance, in
the buildworld load, this change reduces the amount of pmap_remove()
calls by 1/5.
Profiled by: alc
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D16148
SMP systems by extending defined(SMP) to include defined(KLD_MODULE).
This is a regression issue after r335873 .
Discussed with: mmacy@
Sponsored by: Mellanox Technologies
- Change pcpu zone consumers to use a stride size of PAGE_SIZE.
(defined as UMA_PCPU_ALLOC_SIZE to make future identification easier)
- Allocate page from the correct domain for a given cpu.
- Don't initialize pc_domain to non-zero value if NUMA is not defined
There are some misconceptions surrounding this field. It is the
_VM_ NUMA domain and should only ever correspond to valid domain
values as understood by the VM.
The former slab size of sizeof(struct pcpu) was somewhat arbitrary.
The new value is PAGE_SIZE because that's the smallest granularity
which the VM can allocate a slab for a given domain. If you have
fewer than PAGE_SIZE/8 counters on your system there will be some
memory wasted, but this is obviously something where you want the
cache line to be coming from the correct domain.
Reviewed by: jeff
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D15933
- inline atomics in modules on i386 and amd64 (they were always
inline on other arches)
- allow modules to opt in to inlining locks by specifying
MODULE_TIED=1 in the makefile
Reviewed by: kib
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D16079
- increase pmc cpuid field from 8 to 12 bits
- add cpuid version string to initialize entry in the log
so that filter can identify which counter index an
event name maps to
- GC unused config flags
- make fixed counter assignment more robust as well as the
changes needed to be properly identified for filter
time, especially for SMP. If configured, it turns itself on at boot
time for calibration, so is fragile even if never otherwise used.
Both types of kernel profiling were supposed to use a global spinlock
in the SMP case. If hi-res profiling is configured (but not necessarily
used), this was supposed to be optimized by only using it when
necessary, and slightly more efficiently, in asm. But it was not done
at all for mcount entry where it is necessary. This caused crashes
in the SMP case when either type of profiling was enabled. For mcount
exit, it only caused wrong times. The times were wrongest with an
i8254 timer since using that requires exclusive access to the hardware.
The i8254 timer was too slow to use here 20 years ago and is much less
usable now, but it is the default for the SMP case since TSCs weren't
invariant when SMP was new. Do the locking in all hi-res SMP cases for
simplicity.
Calibration uses special asms, and the clobber lists in these were sort
of inverted. They contained the arg and return registers which are not
clobbered, but on amd64 they didn't contain the residue of the call-used
registers which may be clobbered (%r10 and %r11). This usually caused
hangs at boot time. This usually affected even the UP case.
kernel profiling remains broken).
memmove() was broken using ALTENTRY(). ALTENTRY() is only different from
ENTRY() in the profiling case, and its use in that case was sort of
backwards. The backwardness magically turned memmove() into memcpy()
instead of completely breaking it. Only the high resolution parts of
profiling itself were broken. Use ordinary ENTRY() for memmove().
Turn bcopy() into a tail call to memmove() to reduce complications.
This gives slightly different pessimizations and profiling lossage.
The pessimizations are minimized by not using a frame pointer() for
bcopy().
Calls to profiling functions from exception trampolines were not
relocated. This caused crashes on the first exception. Fix this using
function pointers.
Addresses of exception handlers in trampolines were not relocated. This
caused unknown offsets in the profiling data. Relocate by abusing
setidt_disp as for pmc although this is slower than necessary and
requires namespace pollution. pmc seems to be missing some relocations.
Stack traces and lots of other things in debuggers need similar relocations.
Most user addresses were misclassified as unknown kernel addresses and
then ignored. Treat all unknown addresses as user. Now only user
addresses in the kernel text range are significantly misclassified (as
known kernel addresses).
The ibrs functions didn't preserve enough registers. This is the only
recent breakage on amd64. Although these functions are written in
asm, in the profiling case they call profiling functions which are
mostly for the C ABI, so they only have to save call-used registers.
They also have to save arg and return registers in some cases and
actually save them in all cases to reduce complications. They end up
saving all registers except %ecx on i386 and %r10 and %r11 on amd64.
Saving these is only needed for 1 caller on each of amd64 and i386.
Save them there. This is slightly simpler.
Remove saving %ecx in handle_ibrs_exit on i386. Both handle_ibrs_entry
and handle_ibrs_exit use %ecx, but only the latter needed to or did
save it. But saving it there doesn't work for the profiling case.
amd64 has more automatic saving of the most common scratch registers
%rax, %rcx and %rdx (its complications for %r10 are from unusual use
of %r10 by SYSCALL). Thus profiling of handle_ibrs_exit_rs() was not
broken, and I didn't simplify the saving by moving the saving of these
registers from it to the caller.
Intel now provides comprehensive tables for all performance counters
and the various valid configuration permutations as text .json files.
Libpmc has been converted to use these and hwpmc_core has been greatly
simplified by moving to passthrough of the table values.
The one gotcha is that said tables don't support pentium pro and and pentium
IV. There's very few users of hwpmc on _amd64_ kernels on new hardware. It is
unlikely that anyone is doing low level optimization on 15 year old Intel
hardware. Nonetheless, if someone feels strongly enough to populate the
corresponding tables for p4 and ppro I will reinstate the files in to the
build.
Code for the K8 counters and !x86 architectures remains unchanged.
This is a follow-up to r321483, which disabled -Wmacro-redefined for
some lib/msun tests.
If an application included both fenv.h and ieeefp.h, several macros such
as __fldcw(), __fldenv() were defined in both headers, with slightly
different arguments, leading to conflicts.
Fix this by putting all the common macros in the machine-specific
versions of ieeefp.h. Where needed, update the arguments in places
where the macros are invoked.
This also slightly reduces the differences between the amd64 and i386
versions of ieeefp.h.
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D15633
While at it add missing _acq_ and _rel_ variants for 64-bit atomic
operations under i386.
Reviewed by: kib @
MFC after: 1 week
Sponsored by: Mellanox Technologies
In particular, stop using pmap_pte() to read non-promoted pte while
walking the page table. pmap_pte() needs to shoot down the kernel
mapping globally which causes IPI broadcast. Since
pmap_extract_and_hold() is used for slow copyin(9), it is very
significant hit for the 4/4 kernels.
Instead, create single purpose per-processor page frame and use it to
locally map page table page inside the critical section, to avoid
reuse of the frame by other thread if context switched.
Measurement demostrated very significant improvements in any load that
utilizes copyin/copyout.
Found and benchmarked by: bde
Sponsored by: The FreeBSD Foundation
The TSC-s are checked and synchronized only if they were good
originally. That is, invariant, synchronized, etc.
This is necessary on an AMD-based system where after a wakeup from STR I
see that BSP clock differs from AP clocks by a count that roughly
corresponds to one second. The APs are in sync with each other. Not
sure if this is a hardware quirk or a firmware bug.
This is what I see after a resume with this change:
SMP: passed TSC synchronization test after adjustment
acpi_timer0: restoring timecounter, ACPI-fast -> TSC-low
Reviewed by: kib
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D15551
r334005: add pc_ibpb_set as it is now referenced by common code
(although presumably not needed on i386 since it has been there
since the first spectre mitigation work on amd64)
r334009: there is no amd64 rflags -> i386 eflags
- Add constants for fields in DR6 and the reserved fields in DR7. Use
these constants instead of magic numbers in most places that use DR6
and DR7.
- Refer to T_TRCTRAP as "debug exception" rather than a "trace trap"
as it is not just for trace exceptions.
- Always read DR6 for debug exceptions and only clear TF in the flags
register for user exceptions where DR6.BS is set.
- Clear DR6 before returning from a debug exception handler as
recommended by the SDM dating all the way back to the 386. This
allows debuggers to determine the cause of each exception. For
kernel traps, clear DR6 in the T_TRCTRAP case and pass DR6 by value
to other parts of the handler (namely, user_dbreg_trap()). For user
traps, wait until after trapsignal to clear DR6 so that userland
debuggers can read DR6 via PT_GETDBREGS while the thread is stopped
in trapsignal().
Reviewed by: kib, rgrimes
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D15189
is executed on the right stack already. No copy from the entry stack
to the kstack must be performed for vm86 bios call code to function.
To access the pcb flags on kernel entry, unconditionally switch to
kernel address space if vm86 mode is detected.
This fixes very early vm86 bios calls, typically done when boot is
performed by boot2 without loader, and kernel falls back to BIOS calls
to get SMAP.
Reported by: bde
Sponsored by: The FreeBSD Foundation
Use proper method to access userspace. For now, only the slow copyout
path is implemented.
Reported and tested by: tijl (previous version)
Sponsored by: The FreeBSD Foundation
