Re: [Qemu-devel] [PATCH 03/11] S/390 fake TCG implementation

[Aurelien Jarno]

On Mon, Nov 30, 2009 at 11:27:53PM +0100, Alexander Graf wrote:
> 
> On 30.11.2009, at 19:18, Aurelien Jarno wrote:
> 
> > On Thu, Nov 26, 2009 at 02:23:12PM +0100, Alexander Graf wrote:
> >> Qemu won't let us run a KVM target without having host TCG support. Well, 
> >> for
> >> now we don't have any so let's implement a fake target that only stubs out
> >> everything.
> >> 
> >> I tried to keep the patch as close to Uli's source as possible, so whenever
> >> he feels like it he can easily diff his version against this one.
> > 
> > Please find the comments below.
> > 
> >> Signed-off-by: Alexander Graf <address@hidden>
> >> ---
> >> dyngen-exec.h         |    2 +-
> >> target-s390x/helper.c |    5 ++
> >> tcg/s390/tcg-target.c |  103 
> >> +++++++++++++++++++++++++++++++++++++++++++++++++
> >> tcg/s390/tcg-target.h |   48 +++++++++++++++++++++++
> >> 4 files changed, 157 insertions(+), 1 deletions(-)
> >> create mode 100644 tcg/s390/tcg-target.c
> >> create mode 100644 tcg/s390/tcg-target.h
> >> 
> >> diff --git a/dyngen-exec.h b/dyngen-exec.h
> >> index 86e61c3..0353f36 100644
> >> --- a/dyngen-exec.h
> >> +++ b/dyngen-exec.h
> >> @@ -117,7 +117,7 @@ extern int printf(const char *, ...);
> >> 
> >> /* The return address may point to the start of the next instruction.
> >>    Subtracting one gets us the call instruction itself.  */
> >> -#if defined(__s390__)
> >> +#if defined(__s390__) && !defined(__s390x__)
> >> # define GETPC() ((void*)(((unsigned long)__builtin_return_address(0) & 
> >> 0x7fffffffUL) - 1))
> >> #elif defined(__arm__)
> >> /* Thumb return addresses have the low bit set, so we need to subtract two.
> >> diff --git a/target-s390x/helper.c b/target-s390x/helper.c
> >> index 4e23b4a..0e222e3 100644
> >> --- a/target-s390x/helper.c
> >> +++ b/target-s390x/helper.c
> >> @@ -44,6 +44,11 @@ CPUS390XState *cpu_s390x_init(const char *cpu_model)
> >>     return env;
> >> }
> >> 
> >> +target_phys_addr_t cpu_get_phys_page_debug(CPUState *env, target_ulong 
> >> addr)
> >> +{
> >> +    return addr;
> >> +}
> >> +
> > 
> > Why does it appear in this patch? It has nothing to do with TCG support.
> 
> I don't remember. What is this used for anyways?

If it is not used, maybe it's better to remove it.

> >> void cpu_reset(CPUS390XState *env)
> >> {
> >>     if (qemu_loglevel_mask(CPU_LOG_RESET)) {
> >> diff --git a/tcg/s390/tcg-target.c b/tcg/s390/tcg-target.c
> >> new file mode 100644
> >> index 0000000..53bbf69
> >> --- /dev/null
> >> +++ b/tcg/s390/tcg-target.c
> >> @@ -0,0 +1,103 @@
> >> +/*
> >> + * Tiny Code Generator for QEMU
> >> + *
> >> + * Copyright (c) 2009 Ulrich Hecht <address@hidden>
> >> + *
> >> + * Permission is hereby granted, free of charge, to any person obtaining 
> >> a copy
> >> + * of this software and associated documentation files (the "Software"), 
> >> to deal
> >> + * in the Software without restriction, including without limitation the 
> >> rights
> >> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or 
> >> sell
> >> + * copies of the Software, and to permit persons to whom the Software is
> >> + * furnished to do so, subject to the following conditions:
> >> + *
> >> + * The above copyright notice and this permission notice shall be 
> >> included in
> >> + * all copies or substantial portions of the Software.
> >> + *
> >> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
> >> EXPRESS OR
> >> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
> >> MERCHANTABILITY,
> >> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> >> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 
> >> OTHER
> >> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
> >> ARISING FROM,
> >> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 
> >> IN
> >> + * THE SOFTWARE.
> >> + */
> >> +
> >> +static const int tcg_target_reg_alloc_order[] = {
> >> +};
> >> +
> >> +static const int tcg_target_call_iarg_regs[] = {
> >> +};
> >> +
> >> +static const int tcg_target_call_oarg_regs[] = {
> >> +};
> >> +
> >> +static void patch_reloc(uint8_t *code_ptr, int type,
> >> +                tcg_target_long value, tcg_target_long addend)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> +
> >> +static inline int tcg_target_get_call_iarg_regs_count(int flags)
> >> +{
> >> +    tcg_abort();
> >> +    return 0;
> >> +}
> >> +
> >> +/* parse target specific constraints */
> >> +static int target_parse_constraint(TCGArgConstraint *ct, const char 
> >> **pct_str)
> >> +{
> >> +    tcg_abort();
> >> +    return 0;
> >> +}
> >> +
> >> +/* Test if a constant matches the constraint. */
> >> +static inline int tcg_target_const_match(tcg_target_long val,
> >> +                const TCGArgConstraint *arg_ct)
> >> +{
> >> +    tcg_abort();
> >> +    return 0;
> >> +}
> >> +
> >> +/* load a register with an immediate value */
> >> +static inline void tcg_out_movi(TCGContext *s, TCGType type,
> >> +                int ret, tcg_target_long arg)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> +
> >> +/* load data without address translation or endianness conversion */
> >> +static inline void tcg_out_ld(TCGContext *s, TCGType type, int arg,
> >> +                int arg1, tcg_target_long arg2)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> +
> >> +static inline void tcg_out_st(TCGContext *s, TCGType type, int arg,
> >> +                              int arg1, tcg_target_long arg2)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> +
> >> +static inline void tcg_out_op(TCGContext *s, int opc,
> >> +                const TCGArg *args, const int *const_args)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> +
> >> +void tcg_target_init(TCGContext *s)
> >> +{
> >> +}
> > 
> > This is probably here that tcg_abort() is actually the most important.
> > 
> >> +
> >> +void tcg_target_qemu_prologue(TCGContext *s)
> >> +{
> >> +}
> >> +
> > 
> > Also adding it here doesn't cost a lot.
> 
> Both places get called with KVM as well. If I call tcg_abort() here KVM 
> doesn't start.

Then can you add a comment explaining that code is missing.

I am very reluctant in introducing missing/wrong code in qemu.
Experience has shown that it stays for a very long time, until someone
spend hours or days trying to debug an issue.

> > 
> >> +static inline void tcg_out_mov(TCGContext *s, int ret, int arg)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> +
> >> +static inline void tcg_out_addi(TCGContext *s, int reg, tcg_target_long 
> >> val)
> >> +{
> >> +    tcg_abort();
> >> +}
> >> diff --git a/tcg/s390/tcg-target.h b/tcg/s390/tcg-target.h
> >> new file mode 100644
> >> index 0000000..2e66553
> >> --- /dev/null
> >> +++ b/tcg/s390/tcg-target.h
> >> @@ -0,0 +1,48 @@
> >> +/*
> >> + * Tiny Code Generator for QEMU
> >> + *
> >> + * Copyright (c) 2009 Ulrich Hecht <address@hidden>
> >> + *
> >> + * Permission is hereby granted, free of charge, to any person obtaining 
> >> a copy
> >> + * of this software and associated documentation files (the "Software"), 
> >> to deal
> >> + * in the Software without restriction, including without limitation the 
> >> rights
> >> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or 
> >> sell
> >> + * copies of the Software, and to permit persons to whom the Software is
> >> + * furnished to do so, subject to the following conditions:
> >> + *
> >> + * The above copyright notice and this permission notice shall be 
> >> included in
> >> + * all copies or substantial portions of the Software.
> >> + *
> >> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
> >> EXPRESS OR
> >> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
> >> MERCHANTABILITY,
> >> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> >> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 
> >> OTHER
> >> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
> >> ARISING FROM,
> >> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 
> >> IN
> >> + * THE SOFTWARE.
> >> + */
> >> +#define TCG_TARGET_S390 1
> >> +
> >> +#define TCG_TARGET_REG_BITS 64
> >> +#define TCG_TARGET_WORDS_BIGENDIAN
> >> +
> >> +#define TCG_TARGET_NB_REGS 0
> >> +
> >> +enum {
> >> +    TCG_AREG0 = 0,
> >> +};
> > 
> > As this is defined in Uli's patch, I think it might be a good idea to
> > define that correctly. Same for the list of registers.
> 
> I wasn't sure how much of the real architecture I should actually keep. So 
> you think registers belong in?

Again what chokes me is that it introduces wrong code. Especially
TCG_AREG0 = 0. Introducing the registers will fix that.

> >> +/* used for function call generation */
> >> +#define TCG_REG_CALL_STACK                0
> >> +#define TCG_TARGET_STACK_ALIGN            8
> >> +#define TCG_TARGET_CALL_STACK_OFFSET      0
> >> +
> >> +static inline void flush_icache_range(unsigned long start, unsigned long 
> >> stop)
> >> +{
> >> +#if QEMU_GNUC_PREREQ(4, 1)
> >> +    void __clear_cache(char *beg, char *end);
> >> +    __clear_cache((char *) start, (char *) stop);
> > 
> > You should use __builtin___clear_cache instead to avoid having to
> > declare the function.
> 
> Oh, ok :)
> 
> Alex

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net