In icount mode, instructions that access io memory spaces in the middle
of the translation block invoke TB recompilation. After recompilation,
such instructions become last in the TB and are allowed to access io
memory spaces.
When the code includes instruction like i386 'xchg eax, 0xffffd080'
which accesses APIC, QEMU goes into an infinite loop of the recompilation.
This instruction includes two memory accesses - one read and one write.
After the first access, APIC calls cpu_report_tpr_access, which restores
the CPU state to get the current eip. But cpu_restore_state_from_tb
resets the cpu->can_do_io flag which makes the second memory access invalid.
Therefore the second memory access causes a recompilation of the block.
Then these operations repeat again and again.
This patch moves resetting cpu->can_do_io flag from
cpu_restore_state_from_tb to cpu_loop_exit* functions.
It also adds a parameter for cpu_restore_state which controls restoring
icount. There is no need to restore icount when we only query CPU state
without breaking the TB. Restoring it in such cases leads to the
incorrect flow of the virtual time.
In most cases new parameter is true (icount should be recalculated).
But there are two cases in i386 and openrisc when the CPU state is only
queried without the need to break the TB. This patch fixes both of
these cases.
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <20180409091320.12504.35329.stgit@pasha-VirtualBox>
[rth: Make can_do_io setting unconditional; move from cpu_exec;
make cpu_loop_exit_{noexc,restore} call cpu_loop_exit.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
exec-all.h contains TCG-specific definitions. It is not needed outside
TCG-specific files such as translate.c, exec.c or *helper.c.
One generic function had snuck into include/exec/exec-all.h; move it to
include/qom/cpu.h.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix off-by-one error in ITC Tag read.
Remove the switch as we just want to check if index is in valid range
rather than test against list of values.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Bypass View does not cause issuing thread to block and does not affect
any of the cells state bit.
Read from a FIFO cell returns the value of the oldest entry.
Store to a FIFO cell changes the value of the newest entry.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
P/V Synchronized and Try Views can be used to access Semaphore cells.
Load returns current value and post-decrements the value in the cell
(until it reaches zero). Stores increment the value (until it saturates
at 0xFFFF).
P/V Synchronized View causes the issuing thread to block on read if value
is 0. P/V Try View does not block the thread, it returns 0 in this case.
Cell's Empty and Full bits are not modified.
Trap bit (i.e. Gating Storage exceptions) not implemented.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Empty/Full Synchronized and Try views can be used to access FIFO cells.
Store to the FIFO cell pushes the value into the queue, load pops the oldest
element from the queue. Cell's Full and Empty bits are automatically updated
to reflect new state of the cell.
Empty/Full Synchronized View causes the issuing thread to block when FIFO is
empty while thread is performing a read, or FIFO is full while thread is
performing a write.
Empty/Full Try View never blocks the thread. If cell is full then write is
ignored, if cell is empty then load returns 0.
Trap bit (i.e. Gating Storage exceptions) not implemented.
Store Conditional support for E/F Try View (i.e. indicate failure if FIFO
is full) not implemented.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Control view is used to access the ITC Storage Cell Tags. It never causes
the issuing thread to block.
Guest can empty the FIFO cell by setting Empty bit to 1.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Implement ITC as a single object consisting of two memory regions:
1) tag_io: ITC Configuration Tags (i.e. ITCAddressMap{0,1} registers) which
are accessible by the CPU via CACHE instruction. Also adding
MemoryRegion *itc_tag to the CPUMIPSState so that CACHE instruction will
dispatch reads/writes directly.
2) storage_io: memory-mapped ITC Storage whose address space is configurable
(i.e. enabled/remapped/resized) by writing to ITCAddressMap{0,1} registers.
ITC Storage contains FIFO and Semaphore cells. Read-only FIFO bit in the
ITC cell tag indicates the type of the cell. If the ITC Storage contains
both types of cells then FIFOs are located before Semaphores.
Since issuing thread can get blocked on the access to a cell (in E/F
Synchronized and P/V Synchronized Views) each cell has a bitmap to track
which threads are currently blocked.
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
