Re: [PATCH v11 02/10] hvf: Add execute to dirty log permission bitmap

From: Peter Maydell <peter.maydell@linaro.org>
To: Alexander Graf <agraf@csgraf.de>
Cc: "Eduardo Habkost" <ehabkost@redhat.com>,
	"Sergio Lopez" <slp@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"Cameron Esfahani" <dirty@apple.com>,
	"Roman Bolshakov" <r.bolshakov@yadro.com>,
	qemu-arm <qemu-arm@nongnu.org>, "Frank Yang" <lfy@google.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Peter Collingbourne" <pcc@google.com>
Subject: Re: [PATCH v11 02/10] hvf: Add execute to dirty log permission bitmap
Date: Thu, 16 Sep 2021 15:05:21 +0100	[thread overview]
Message-ID: <CAFEAcA9+mRkGwHTnHzRrhAFRKj=NM3Yj_tsMskGjNE+=fzdf3w@mail.gmail.com> (raw)
In-Reply-To: <2b3f4581-56c3-db0e-f083-fd6d1b7cc2f8@csgraf.de>

On Thu, 16 Sept 2021 at 15:04, Alexander Graf <agraf@csgraf.de> wrote:
>
>
> On 16.09.21 13:59, Peter Maydell wrote:
> > On Wed, 15 Sept 2021 at 19:10, Alexander Graf <agraf@csgraf.de> wrote:
> >> Hvf's permission bitmap during and after dirty logging does not include
> >> the HV_MEMORY_EXEC permission. At least on Apple Silicon, this leads to
> >> instruction faults once dirty logging was enabled.
> >>
> >> Add the bit to make it work properly.
> >>
> >> Signed-off-by: Alexander Graf <agraf@csgraf.de>
> >> ---
> >>  accel/hvf/hvf-accel-ops.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/accel/hvf/hvf-accel-ops.c b/accel/hvf/hvf-accel-ops.c
> >> index d1691be989..71cc2fa70f 100644
> >> --- a/accel/hvf/hvf-accel-ops.c
> >> +++ b/accel/hvf/hvf-accel-ops.c
> >> @@ -239,12 +239,12 @@ static void hvf_set_dirty_tracking(MemoryRegionSection *section, bool on)
> >>      if (on) {
> >>          slot->flags |= HVF_SLOT_LOG;
> >>          hv_vm_protect((uintptr_t)slot->start, (size_t)slot->size,
> >> -                      HV_MEMORY_READ);
> >> +                      HV_MEMORY_READ | HV_MEMORY_EXEC);
> >>      /* stop tracking region*/
> >>      } else {
> >>          slot->flags &= ~HVF_SLOT_LOG;
> >>          hv_vm_protect((uintptr_t)slot->start, (size_t)slot->size,
> >> -                      HV_MEMORY_READ | HV_MEMORY_WRITE);
> >> +                      HV_MEMORY_READ | HV_MEMORY_WRITE | HV_MEMORY_EXEC);
> >>      }
> >>  }
> > Makes sense -- this matches the premissions we set initially
> > for memory regions in hvf_set_phys_mem().
> >
> > Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> >
> > Should we change also the hv_vm_protect() call in
> > target/i386/hvf/hvf.c:ept_emulation_fault(), for consistency ?
>
>
> The x86 hvf code seems to deal just fine with !X mappings, so I'd leave
> it as is as part of the arm enablement series - especially because I
> have limited testing capabilities for x86 hvf.

Yeah, I should have been clearer -- that would be best as
a separate x86-specific patch.

-- PMM