The purpose of virtio-9p-test is to test the virtio-9p device, especially
the 9p server state machine. We don't really care what fsdev backend we're
using. Moreover, if we want to be able to test the flush request or a
device reset with in-flights I/O, it is close to impossible to achieve
with a physical backend because we cannot ask it reliably to put an I/O
on hold at a specific point in time.
Fortunately, we can do that with the synthetic backend, which allows to
register callbacks on read/write accesses to a specific file. This will
be used by a later patch to test the 9P flush request.
The walk request test is converted to using the synth backend.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
In order to test request cancellation, we will need to send multiple
requests and wait for the associated replies. Since we poll the ISR
to know if a request completed, we may have several replies to parse
when we detect ISR was set to 1.
This patch moves the waiting out of the reply parsing path, up into
the functional tests.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
It doesn't really makes sense to hide the request tag from the test
functions. It prevents to test the 9p server behavior when passed
a wrong tag (ie, still in use or different from P9_NOTAG for a
version request). Also the spec says that a tag is reusable as soon
as the corresponding request was replied or flushed: no need to
always increment tags like we do now. And finaly, an upcoming test
of the flush command will need to manipulate tags explicitely.
This simply changes all request functions to have a tag argument.
Except for the version request which needs P9_NOTAG, all other
tests can pass 0 since they wait for the reply before sending
another request.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
# Background
I was investigating spurious non-deterministic EINTR returns from
various 9p file system operations in a Linux guest served from the
qemu 9p server.
## EINTR, ERESTARTSYS and the linux kernel
When a signal arrives that the Linux kernel needs to deliver to user-space
while a given thread is blocked (in the 9p case waiting for a reply to its
request in 9p_client_rpc -> wait_event_interruptible), it asks whatever
driver is currently running to abort its current operation (in the 9p case
causing the submission of a TFLUSH message) and return to user space.
In these situations, the error message reported is generally ERESTARTSYS.
If the userspace processes specified SA_RESTART, this means that the
system call will get restarted upon completion of the signal handler
delivery (assuming the signal handler doesn't modify the process state
in complicated ways not relevant here). If SA_RESTART is not specified,
ERESTARTSYS gets translated to EINTR and user space is expected to handle
the restart itself.
## The 9p TFLUSH command
The 9p TFLUSH commands requests that the server abort an ongoing operation.
The man page [1] specifies:
```
If it recognizes oldtag as the tag of a pending transaction, it should
abort any pending response and discard that tag.
[...]
When the client sends a Tflush, it must wait to receive the corresponding
Rflush before reusing oldtag for subsequent messages. If a response to the
flushed request is received before the Rflush, the client must honor the
response as if it had not been flushed, since the completed request may
signify a state change in the server
```
In particular, this means that the server must not send a reply with the
orignal tag in response to the cancellation request, because the client is
obligated to interpret such a reply as a coincidental reply to the original
request.
# The bug
When qemu receives a TFlush request, it sets the `cancelled` flag on the
relevant pdu. This flag is periodically checked, e.g. in
`v9fs_co_name_to_path`, and if set, the operation is aborted and the error
is set to EINTR. However, the server then violates the spec, by returning
to the client an Rerror response, rather than discarding the message
entirely. As a result, the client is required to assume that said Rerror
response is a result of the original request, not a result of the
cancellation and thus passes the EINTR error back to user space.
This is not the worst thing it could do, however as discussed above, the
correct error code would have been ERESTARTSYS, such that user space
programs with SA_RESTART set get correctly restarted upon completion of
the signal handler.
Instead, such programs get spurious EINTR results that they were not
expecting to handle.
It should be noted that there are plenty of user space programs that do not
set SA_RESTART and do not correctly handle EINTR either. However, that is
then a userspace bug. It should also be noted that this bug has been
mitigated by a recent commit to the Linux kernel [2], which essentially
prevents the kernel from sending Tflush requests unless the process is about
to die (in which case the process likely doesn't care about the response).
Nevertheless, for older kernels and to comply with the spec, I believe this
change is beneficial.
# Implementation
The fix is fairly simple, just skipping notification of a reply if
the pdu was previously cancelled. We do however, also notify the transport
layer that we're doing this, so it can clean up any resources it may be
holding. I also added a new trace event to distinguish
operations that caused an error reply from those that were cancelled.
One complication is that we only omit sending the message on EINTR errors in
order to avoid confusing the rest of the code (which may assume that a
client knows about a fid if it sucessfully passed it off to pud_complete
without checking for cancellation status). This does mean that if the server
acts upon the cancellation flag, it always needs to set err to EINTR. I
believe this is true of the current code.
[1] https://9fans.github.io/plan9port/man/man9/flush.html
[2] https://github.com/torvalds/linux/commit/9523feac272ccad2ad8186ba4fcc891
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
[groug, send a zero-sized reply instead of detaching the buffer]
Signed-off-by: Greg Kurz <groug@kaod.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
No good reasons to do this outside of v9fs_device_realize_common().
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
We masked the wrong bits, which prevented some of the
32-bit R registers. E.g. "fcnvxf,sgl,sgl fr22R,fr6R".
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Now that we have the prerequisites in target/hppa/,
implement the hardware for a PA7100LC.
This also enables build for hppa-softmmu.
Signed-off-by: Helge Deller <deller@gmx.de>
[rth: Since it is all new code, squashed all branch development
withing hw/hppa/ to a single patch.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This is an extension to the base ISA, but we can use this in
the kernel idle loop to reduce the host cpu time consumed.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
HP-UX 10.20 CD contains "add r0, r0, r27" in a delay slot,
which uses at least 5 temps.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Unknown why this works, but if we return EXCP_ITLB_MISS we
will triple-fault the first userland instruction fetch.
Is it something to do with having a combined I/DTLB?
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Linux sets sr4-sr7 all to the same value, which means that we
need not do any runtime computation to find out what space to
use in forming the GVA.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Real hardware would use an external device to control the power.
But for the moment let's invent instructions in reserved space,
to be used by our custom firmware.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
However since HPPA has a software-managed TLB, and the relevant
TLB manipulation instructions are not implemented, this does not
actually do anything.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Any one TB will have only one space value. If we change spaces,
we change TBs. Thus BE and BEV must exit the TB immediately.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
These instructions force the destination privilege level
of the branch destination to be no higher than current.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This changes the system virtual address width to 64-bit and
incorporates the space registers into load/store operations.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
While the E bit is only used for pa2.0 mfctl,w from sar,
the otherwise reserved bit does not appear to be decoded.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Most aspects of privilege are not yet handled. But this
gives us the start from which to begin checking.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
For system mode, we will need 64-bit virtual addresses even when
we have 32-bit register sizes. Since the rest of QEMU equates
TARGET_LONG_BITS with the address size, redefine everything
related to register size in terms of a new TARGET_REGISTER_BITS.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
We don't actually do anything with most of the bits yet,
but at least they have names and we have somewhere to
store them.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
With the addition of default-configs/hppa-softmmu.mak, this
will compile. It is not enabled with this patch, however.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
