accel/tcg: Add stub for probe_access()

[PATCH] accel/tcg: Add stub for probe_access()

Posted by Philippe Mathieu-Daudé 4 years ago

The TCG helpers where added in b92e5a22ec3 in softmmu_template.h.
probe_write() was added in there in 3b4afc9e75a to be moved out
to accel/tcg/cputlb.c in 3b08f0a9254, and was later refactored
as probe_access() in c25c283df0f.
Since it is a TCG specific helper, add a stub to avoid failures
when building without TCG, such:

  target/arm/helper.o: In function `probe_read':
  include/exec/exec-all.h:345: undefined reference to `probe_access'

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
Cc: Richard Henderson <rth@twiddle.net>
Cc: Emilio G. Cota <cota@braap.org>
Cc: Alex Bennée <alex.bennee@linaro.org>
Cc: David Hildenbrand <david@redhat.com>
---
 accel/stubs/tcg-stub.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/accel/stubs/tcg-stub.c b/accel/stubs/tcg-stub.c
index 677191a69c..e4bbf997aa 100644
--- a/accel/stubs/tcg-stub.c
+++ b/accel/stubs/tcg-stub.c
@@ -22,3 +22,10 @@ void tb_flush(CPUState *cpu)
 void tlb_set_dirty(CPUState *cpu, target_ulong vaddr)
 {
 }
+
+void *probe_access(CPUArchState *env, target_ulong addr, int size,
+                   MMUAccessType access_type, int mmu_idx, uintptr_t retaddr)
+{
+     /* Handled by hardware accelerator. */
+     g_assert_not_reached();
+}
-- 
2.21.1

Re: [PATCH] accel/tcg: Add stub for probe_access()

Posted by David Hildenbrand 4 years ago

On 23.04.20 09:10, Philippe Mathieu-Daudé wrote:
> The TCG helpers where added in b92e5a22ec3 in softmmu_template.h.
> probe_write() was added in there in 3b4afc9e75a to be moved out
> to accel/tcg/cputlb.c in 3b08f0a9254, and was later refactored
> as probe_access() in c25c283df0f.
> Since it is a TCG specific helper, add a stub to avoid failures
> when building without TCG, such:
> 
>   target/arm/helper.o: In function `probe_read':
>   include/exec/exec-all.h:345: undefined reference to `probe_access'

I think you're missing the most important commit:

0d57b4999220 ("target/arm: Add support for DC CVAP & DC CVADP ins")

I do wonder if dccvap_writefn() and calling code should be compiled for
TCG only (CONFIG_TCG). I assume it is only called from TCG code -
otherwise it would already be semi-broken.

> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Emilio G. Cota <cota@braap.org>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Cc: David Hildenbrand <david@redhat.com>
> ---
>  accel/stubs/tcg-stub.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/accel/stubs/tcg-stub.c b/accel/stubs/tcg-stub.c
> index 677191a69c..e4bbf997aa 100644
> --- a/accel/stubs/tcg-stub.c
> +++ b/accel/stubs/tcg-stub.c
> @@ -22,3 +22,10 @@ void tb_flush(CPUState *cpu)
>  void tlb_set_dirty(CPUState *cpu, target_ulong vaddr)
>  {
>  }
> +
> +void *probe_access(CPUArchState *env, target_ulong addr, int size,
> +                   MMUAccessType access_type, int mmu_idx, uintptr_t retaddr)
> +{
> +     /* Handled by hardware accelerator. */
> +     g_assert_not_reached();
> +}
> 

Still, this makes sense to me as well

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb

Re: [PATCH] accel/tcg: Add stub for probe_access()

Posted by Philippe Mathieu-Daudé 4 years ago

On Thu, Apr 23, 2020 at 9:49 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 23.04.20 09:10, Philippe Mathieu-Daudé wrote:
> > The TCG helpers where added in b92e5a22ec3 in softmmu_template.h.
> > probe_write() was added in there in 3b4afc9e75a to be moved out
> > to accel/tcg/cputlb.c in 3b08f0a9254, and was later refactored
> > as probe_access() in c25c283df0f.
> > Since it is a TCG specific helper, add a stub to avoid failures
> > when building without TCG, such:
> >
> >   target/arm/helper.o: In function `probe_read':
> >   include/exec/exec-all.h:345: undefined reference to `probe_access'
>
> I think you're missing the most important commit:
>
> 0d57b4999220 ("target/arm: Add support for DC CVAP & DC CVADP ins")
>
> I do wonder if dccvap_writefn() and calling code should be compiled for
> TCG only (CONFIG_TCG). I assume it is only called from TCG code -
> otherwise it would already be semi-broken.

I can only recommend you to read the thread after this previous patch,
as I don't have the knowledge to explain...:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg689115.html

>
> >
> > Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> > ---
> > Cc: Richard Henderson <rth@twiddle.net>
> > Cc: Emilio G. Cota <cota@braap.org>
> > Cc: Alex Bennée <alex.bennee@linaro.org>
> > Cc: David Hildenbrand <david@redhat.com>
> > ---
> >  accel/stubs/tcg-stub.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/accel/stubs/tcg-stub.c b/accel/stubs/tcg-stub.c
> > index 677191a69c..e4bbf997aa 100644
> > --- a/accel/stubs/tcg-stub.c
> > +++ b/accel/stubs/tcg-stub.c
> > @@ -22,3 +22,10 @@ void tb_flush(CPUState *cpu)
> >  void tlb_set_dirty(CPUState *cpu, target_ulong vaddr)
> >  {
> >  }
> > +
> > +void *probe_access(CPUArchState *env, target_ulong addr, int size,
> > +                   MMUAccessType access_type, int mmu_idx, uintptr_t retaddr)
> > +{
> > +     /* Handled by hardware accelerator. */
> > +     g_assert_not_reached();
> > +}
> >
>
> Still, this makes sense to me as well
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
>
> --
> Thanks,
>
> David / dhildenb
>

Re: [PATCH] accel/tcg: Add stub for probe_access()

Posted by David Hildenbrand 4 years ago

On 23.04.20 09:59, Philippe Mathieu-Daudé wrote:
> On Thu, Apr 23, 2020 at 9:49 AM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 23.04.20 09:10, Philippe Mathieu-Daudé wrote:
>>> The TCG helpers where added in b92e5a22ec3 in softmmu_template.h.
>>> probe_write() was added in there in 3b4afc9e75a to be moved out
>>> to accel/tcg/cputlb.c in 3b08f0a9254, and was later refactored
>>> as probe_access() in c25c283df0f.
>>> Since it is a TCG specific helper, add a stub to avoid failures
>>> when building without TCG, such:
>>>
>>>   target/arm/helper.o: In function `probe_read':
>>>   include/exec/exec-all.h:345: undefined reference to `probe_access'
>>
>> I think you're missing the most important commit:
>>
>> 0d57b4999220 ("target/arm: Add support for DC CVAP & DC CVADP ins")
>>
>> I do wonder if dccvap_writefn() and calling code should be compiled for
>> TCG only (CONFIG_TCG). I assume it is only called from TCG code -
>> otherwise it would already be semi-broken.
> 
> I can only recommend you to read the thread after this previous patch,
> as I don't have the knowledge to explain...:
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg689115.html

Yeah, me neither. Sounds wrong to me to have TCG-only code stick around
in !CONFIG_TCG builds. But I am pretty sure ARM people know what they
are doing.


-- 
Thanks,

David / dhildenb

Re: [PATCH] accel/tcg: Add stub for probe_access()

Posted by Paolo Bonzini 4 years ago

On 23/04/20 10:04, David Hildenbrand wrote:
>> I can only recommend you to read the thread after this previous patch,
>> as I don't have the knowledge to explain...:
>> https://www.mail-archive.com/qemu-devel@nongnu.org/msg689115.html
> Yeah, me neither. Sounds wrong to me to have TCG-only code stick around
> in !CONFIG_TCG builds. But I am pretty sure ARM people know what they
> are doing.

It's better if helpers are left out via obj-$(CONFIG_TCG), but it's not
the end of the world if they aren't---as long as it compiles of course!

This case is definitely borderline.

Paolo