Remove need for explicit `Config::async_support` knob (#12371)

* Refactor component model host function definitions

Push the `async`-ness down one layer.

* Remove need for explicit `Config::async

Remove need for explicit `Config::async_support` knob (#12371)

* Refactor component model host function definitions

Push the `async`-ness down one layer.

* Remove need for explicit `Config::async_support` knob

This commit is an attempt to step towards reconciling "old async" and
"new async" in Wasmtime. The old async style is the original async
support in Wasmtime with `call_async`, `func_wrap_async`, etc, where the
main property is that the store is "locked" during an async operation.
Put another way, a store can only execute at most one async operation at
a time. This is in contrast to "new async" support in Wasmtime with the
component-model-async (WASIp3) support, where stores can have more than
one async operation in flight at once.

This commit does not fully reconcile these differences, but it does
remove one hurdle along the way: `Config::async_support`. Since the
beginning of Wasmtime this configuration knob has existed to explicitly
demarcate a config/engine/store as "this thing requires `async` stuff
internally." This has started to make less and less sense over time
where the line between sync and async has become more murky with WASIp3
where the two worlds comingle. The goal of this commit is to deprecate
`Config::async_support` and make the function not actually do anything.

In isolation this can't simply be done, however, because there are many
load-bearing aspects of Wasmtime that rely on this `async_support` knob.
For example once epochs + yielding are enabled it's required that all
Wasm is executed on a fiber lest it hit an epoch and not know how to
yield. That means that this commit is not a simple removal of
`async_support` but instead a refactoring/rearchitecting of how async is
used internally within Wasmtime. The high-level ideas within Wasmtime
now are:

* A `Store` has a "requires async" boolean stored within it.
* All configuration options which end up requiring async, such as
yielding with epochs, turn this boolean on.
* Creation of host functions which use async
(e.g. `func_wrap_{async,concurrent}`) will also turn this option on.
* Synchronous API entrypoints into Wasmtime ensure that this boolean is
disabled.
* Asynchronous APIs are usable at any time.

This means that the concept of an async store vs a sync store is now
gone. All stores are equally capable of executing sync/async, and the
change now is that dynamically some stores will require that async is
used with certain configuration. Additionally all panicking conditions
around `async_support` have been converted to errors instead. All
relevant APIs already returned an error and things are murky enough now
that it's not necessarily trivial to get this right at the embedder
level. In the interest of avoiding panics all detected async mismatches
are now first-class `wasmtime::Error` values.

The end result of this commit is that `Config::async_support` is a
deprecated `#[doc(hidden)]` function that does nothing. While many
internal changes happened as well as having new tests for all this sort
of behavior this is not expected to have a great impact on external
consumers. In general a deletion of `async_support(true)` is in theory
all that's required. This is intended to make it easier to think about
async/sync/etc in the future with WASIp3 and eventually reconcile
`func_wrap_async` and `func_wrap_concurrent` for example. That's left
for future refactorings however.

prtest:full

* Review comments

* Fix CI failures

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Migrate the `wasmtime` crate to `wasmtime_environ::error::*` (#12231)

* Migrate the `wasmtime` crate to `wasmtime_environ::error::*`

Instead of `anyhow::Error`.

This commit re-exports the `wasmtim

Migrate the `wasmtime` crate to `wasmtime_environ::error::*` (#12231)

* Migrate the `wasmtime` crate to `wasmtime_environ::error::*`

Instead of `anyhow::Error`.

This commit re-exports the `wasmtime_environ::error` as the `wasmtime::error`
module, updates the prelude to include these new error-handling types, redirects
our top-level `wasmtime::{Error, Result}` re-exports to re-export
`wasmtime::error::{Error, Result}`, and updates various use sites that were
directly using `anyhow` to use the new `wasmtime` versions.

This process also required updating the component macro and wit-bindgen macro to
use the new error types instead of `anyhow`.

Part of https://github.com/bytecodealliance/wasmtime/issues/12069

* Replace wasmtime::error::Thing with wasmtime::Thing where it makes sense

* cargo fmt

* Move `crate::error::Thing` to `crate::Thing` where it makes sense

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Refactor resetting memory on `MemoryImageSlot` drop (#11510)

* Refactor resetting memory on `MemoryImageSlot` drop

This commit refactors the behavior of dropping a `MemoryImageSlot` to no
longer ma

Refactor resetting memory on `MemoryImageSlot` drop (#11510)

* Refactor resetting memory on `MemoryImageSlot` drop

This commit refactors the behavior of dropping a `MemoryImageSlot` to no
longer map anonymous memory into the slot. This behavior was implemented
previously because if a `MemoryImageSlot` is dropped then the state of
the slot is unknown and to prevent any sort of data leakage a reset is
performed.

This reset operation, however, is fallible in that it calls `mmap`.
Calls to `mmap` can fail due to `ENOMEM`, for example, if the process
has reached its VMA limit. This means that if a process is in a near-OOM
condition then failing to allocate a memory image could panic the
process due to the `unwrap()` in the destructor of `MemoryImageSlot`.
The purpose of this commit is to avoid this `unwrap()` and instead move
the reset behavior to a location where an error can be propagated.

This commit removes the clear-on-drop behavior of `MemoryImageSlot`
slot. This was already disabled everywhere except the pooling allocator.
The pooling allocator now maintains an extra bit of state-per-slot where
instead of storing `Option<MemoryImageSlot>` it now stores effectively
one other variant of "unknown". On reuse of an "unknown" slot the memory
is reset back to an anonymous mapping and this is all done in a context
where an error can be propagated.

Two tests are added in this commit to confirm all of this behavior:

* The first test is a new test that passes both before and after this
commit which performs a failed allocation of a memory slot. A
successful allocation is then made to ensure that the previous image
is not present and zero memory is present. This test fails before the
commit if the clear-on-drop behavior is removed, and it fails with this
commit if the clear-on-reusing-unknown behavior is removed.
Effectively this test ensures that the clear-on-unknown-state logic is
present.

* The second test is a new test that panicked before this commit and
passes afterwards. This second test exhausts all VMAs in the current
process, or at least most of them, and then tries to allocate some
instances with an image. Instance allocation will eventually fail and
cause the erroneous path to get executed. This previously unwrapped a
`ENOMEM` failure, and now it can be handled gracefully by the
embedder.

* Skip the new test on QEMU, it fails on CI

* Only run test on Linux

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Add a configuration knob for `PAGEMAP_SCAN` (#11433)

* Add a configuration knob for `PAGEMAP_SCAN`

This commit adds `PoolingAlloationConfig::pagemap_scan` and additionally
adds `-Opooling-pagemap-s

Add a configuration knob for `PAGEMAP_SCAN` (#11433)

* Add a configuration knob for `PAGEMAP_SCAN`

This commit adds `PoolingAlloationConfig::pagemap_scan` and additionally
adds `-Opooling-pagemap-scan` to configure on the CLI. This is the same
tri-state configuration option as `MpkEnable` so that enum was renamed
to just `Enabled` and repurposed for both options.

This then additionally turns the option off-by-default instead of the
previous on-by-default-if-able-to to enable more slowly rolling out this
feature.

* Fix broken test

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Add support for the Linux PAGEMAP_SCAN ioctl (#11372)

* WIP: use the pagemap_scan ioctl to selectively reset an instance's dirty pages

* Less hacky, and supporting tables, too

* Bugfixes

* WIP: m

Add support for the Linux PAGEMAP_SCAN ioctl (#11372)

* WIP: use the pagemap_scan ioctl to selectively reset an instance's dirty pages

* Less hacky, and supporting tables, too

* Bugfixes

* WIP: memcpy instead of pread

* Refactor support for pagemap

* Don't hold a raw pointer to the original data, plumb through an `Arc`
to have a safe reference instead.
* Update pagemap bindings to latest version of abstraction written.
* Include pagemap-specific tests.
* Use a `PageMap` structure created once-per-pool instead of a
static-with-a-file.
* Refactor to use the "pagemap path" unconditionally which blends in the
keep_resident bits.

* Improve safety documentation

prtest:full

* Fix some lints

* Skip ioctl tests when it's not supported

* Fix a memory leak by moving impls around

* Fix no vm build

* Review comments

* Add more pagemap-specific documentation

* Add more docs, refactor implementation slightly

* Improve `category_*` docs

Basically forward to the Linux kernel source itself.

* Fix compile

* Make pagemap integration resilient across forks

* Fix non-pooling-allocator-build

* Fix portability issues of new test

* Actually use config on macos

---------

Co-authored-by: Till Schneidereit <[email protected]>

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