[Qemu-devel] [PATCH v2 0/3] target-arm: Add a few more S2 MMU input checks

[Qemu-devel] [PATCH v2 0/3] target-arm: Add a few more S2 MMU input checks

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>

This adds the inputsize > pamax check and also fixes the
startlevel checks to apply to the 64bit translations.

Comments welcome!

Cheers,
Edgar

v1 -> v2:
* inputsize > pmax check only applies to AArch64
* Fix commit message typo < should be >

Edgar E. Iglesias (3):
  target-arm: Apply S2 MMU startlevel table size check to AArch64
  target-arm: Make pamax an argument to check_s2_startlevel
  target-arm: Implement the S2 MMU inputsize > pamax check

 target-arm/helper.c | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

-- 
1.9.1

[Qemu-devel] [PATCH v2 1/3] target-arm: Apply S2 MMU startlevel table size check to AArch64

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>

The S2 starting level table size check applies to both AArch32
and AArch64. Move it to common code.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
---
 target-arm/helper.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index f956b67..8aedce9 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -6581,11 +6581,19 @@ typedef enum {
 static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
                                 int inputsize, int stride)
 {
+    const int grainsize = stride + 3;
+    int startsizecheck;
+
     /* Negative levels are never allowed.  */
     if (level < 0) {
         return false;
     }
 
+    startsizecheck = inputsize - ((3 - level) * stride + grainsize);
+    if (startsizecheck < 1 || startsizecheck > stride + 4) {
+        return false;
+    }
+
     if (is_aa64) {
         unsigned int pamax = arm_pamax(cpu);
 
@@ -6609,20 +6617,12 @@ static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
             g_assert_not_reached();
         }
     } else {
-        const int grainsize = stride + 3;
-        int startsizecheck;
-
         /* AArch32 only supports 4KB pages. Assert on that.  */
         assert(stride == 9);
 
         if (level == 0) {
             return false;
         }
-
-        startsizecheck = inputsize - ((3 - level) * stride + grainsize);
-        if (startsizecheck < 1 || startsizecheck > stride + 4) {
-            return false;
-        }
     }
     return true;
 }
-- 
1.9.1

[Qemu-devel] [PATCH v2 2/3] target-arm: Make pamax an argument to check_s2_startlevel

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>

Make pamax an argument to check_s2_startlevel in preparation
for future reuse.

No functional change.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
---
 target-arm/helper.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 8aedce9..4abeb4d 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -6579,7 +6579,8 @@ typedef enum {
  * Returns true if the suggested starting level is OK and false otherwise.
  */
 static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
-                                int inputsize, int stride)
+                                int inputsize, int stride,
+                                unsigned int pamax)
 {
     const int grainsize = stride + 3;
     int startsizecheck;
@@ -6595,8 +6596,6 @@ static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
     }
 
     if (is_aa64) {
-        unsigned int pamax = arm_pamax(cpu);
-
         switch (stride) {
         case 13: /* 64KB Pages.  */
             if (level == 0 || (level == 1 && pamax <= 42)) {
@@ -6808,6 +6807,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
          * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
          */
         int startlevel = extract32(tcr->raw_tcr, 6, 2);
+        unsigned int pamax = arm_pamax(cpu);
         bool ok;
 
         if (va_size == 32 || stride == 9) {
@@ -6820,7 +6820,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
 
         /* Check that the starting level is valid. */
         ok = check_s2_startlevel(cpu, va_size == 64, level,
-                                 inputsize, stride);
+                                 inputsize, stride, pamax);
         if (!ok) {
             /* AArch64 reports these as level 0 faults.
              * AArch32 reports these as level 1 faults.
-- 
1.9.1

[Qemu-devel] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>

Implement the inputsize > pamax check for Stage 2 translations.
We have multiple choices for how to respond to errors and
choose to fault.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
---
 target-arm/helper.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 4abeb4d..9a7ff5e 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -6808,7 +6808,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
          */
         int startlevel = extract32(tcr->raw_tcr, 6, 2);
         unsigned int pamax = arm_pamax(cpu);
-        bool ok;
+        bool ok = true;
 
         if (va_size == 32 || stride == 9) {
             /* AArch32 or 4KB pages */
@@ -6818,9 +6818,17 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
             level = 3 - startlevel;
         }
 
-        /* Check that the starting level is valid. */
-        ok = check_s2_startlevel(cpu, va_size == 64, level,
-                                 inputsize, stride, pamax);
+        if (va_size == 64 &&
+            inputsize > pamax &&
+            (arm_el_is_aa64(env, 1) || inputsize > 40)) {
+            /* We have multiple choices but choose to fault.  */
+            ok = false;
+        }
+        if (ok) {
+            /* Check that the starting level is valid. */
+            ok = check_s2_startlevel(cpu, va_size == 64, level,
+                                     inputsize, stride, pamax);
+        }
         if (!ok) {
             /* AArch64 reports these as level 0 faults.
              * AArch32 reports these as level 1 faults.
-- 
1.9.1

Re: [Qemu-devel] [PATCH v2 2/3] target-arm: Make pamax an argument to check_s2_startlevel

[Alex Bennée]

Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:

> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>
> Make pamax an argument to check_s2_startlevel in preparation
> for future reuse.
>
> No functional change.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> ---
>  target-arm/helper.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 8aedce9..4abeb4d 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -6579,7 +6579,8 @@ typedef enum {
>   * Returns true if the suggested starting level is OK and false otherwise.
>   */
>  static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
> -                                int inputsize, int stride)
> +                                int inputsize, int stride,
> +                                unsigned int pamax)
>  {

If you fix the docstring above you can have my:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>


>      const int grainsize = stride + 3;
>      int startsizecheck;
> @@ -6595,8 +6596,6 @@ static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
>      }
>
>      if (is_aa64) {
> -        unsigned int pamax = arm_pamax(cpu);
> -
>          switch (stride) {
>          case 13: /* 64KB Pages.  */
>              if (level == 0 || (level == 1 && pamax <= 42)) {
> @@ -6808,6 +6807,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>           * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
>           */
>          int startlevel = extract32(tcr->raw_tcr, 6, 2);
> +        unsigned int pamax = arm_pamax(cpu);
>          bool ok;
>
>          if (va_size == 32 || stride == 9) {
> @@ -6820,7 +6820,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>
>          /* Check that the starting level is valid. */
>          ok = check_s2_startlevel(cpu, va_size == 64, level,
> -                                 inputsize, stride);
> +                                 inputsize, stride, pamax);
>          if (!ok) {
>              /* AArch64 reports these as level 0 faults.
>               * AArch32 reports these as level 1 faults.


--
Alex Bennée

Re: [Qemu-devel] [PATCH v2 2/3] target-arm: Make pamax an argument to check_s2_startlevel

[Edgar E. Iglesias]

On Thu, Jan 21, 2016 at 03:54:54PM +0000, Alex Bennée wrote:
> 
> Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:
> 
> > From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
> >
> > Make pamax an argument to check_s2_startlevel in preparation
> > for future reuse.
> >
> > No functional change.
> >
> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> > ---
> >  target-arm/helper.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/target-arm/helper.c b/target-arm/helper.c
> > index 8aedce9..4abeb4d 100644
> > --- a/target-arm/helper.c
> > +++ b/target-arm/helper.c
> > @@ -6579,7 +6579,8 @@ typedef enum {
> >   * Returns true if the suggested starting level is OK and false otherwise.
> >   */
> >  static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
> > -                                int inputsize, int stride)
> > +                                int inputsize, int stride,
> > +                                unsigned int pamax)
> >  {
> 
> If you fix the docstring above you can have my:
> 
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

I've fixed the comment for v3.

Thanks,
Edgar

> 
> 
> >      const int grainsize = stride + 3;
> >      int startsizecheck;
> > @@ -6595,8 +6596,6 @@ static bool check_s2_startlevel(ARMCPU *cpu, bool is_aa64, int level,
> >      }
> >
> >      if (is_aa64) {
> > -        unsigned int pamax = arm_pamax(cpu);
> > -
> >          switch (stride) {
> >          case 13: /* 64KB Pages.  */
> >              if (level == 0 || (level == 1 && pamax <= 42)) {
> > @@ -6808,6 +6807,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >           * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
> >           */
> >          int startlevel = extract32(tcr->raw_tcr, 6, 2);
> > +        unsigned int pamax = arm_pamax(cpu);
> >          bool ok;
> >
> >          if (va_size == 32 || stride == 9) {
> > @@ -6820,7 +6820,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >
> >          /* Check that the starting level is valid. */
> >          ok = check_s2_startlevel(cpu, va_size == 64, level,
> > -                                 inputsize, stride);
> > +                                 inputsize, stride, pamax);
> >          if (!ok) {
> >              /* AArch64 reports these as level 0 faults.
> >               * AArch32 reports these as level 1 faults.
> 
> 
> --
> Alex Bennée

Re: [Qemu-devel] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check

[Alex Bennée]

Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:

> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>
> Implement the inputsize > pamax check for Stage 2 translations.
> We have multiple choices for how to respond to errors and
> choose to fault.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> ---
>  target-arm/helper.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 4abeb4d..9a7ff5e 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -6808,7 +6808,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>           */
>          int startlevel = extract32(tcr->raw_tcr, 6, 2);
>          unsigned int pamax = arm_pamax(cpu);
> -        bool ok;
> +        bool ok = true;
>
>          if (va_size == 32 || stride == 9) {
>              /* AArch32 or 4KB pages */
> @@ -6818,9 +6818,17 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>              level = 3 - startlevel;
>          }
>
> -        /* Check that the starting level is valid. */
> -        ok = check_s2_startlevel(cpu, va_size == 64, level,
> -                                 inputsize, stride, pamax);
> +        if (va_size == 64 &&
> +            inputsize > pamax &&
> +            (arm_el_is_aa64(env, 1) || inputsize > 40)) {

If va_size == 64 doesn't that imply arm_el_is_aa64(env, 1)? Looking
further up the function it seems that is what sets va_size in the first
place. I think that makes the inputsize > 40 check redundant.

> +            /* We have multiple choices but choose to fault.  */
> +            ok = false;
> +        }
> +        if (ok) {
> +            /* Check that the starting level is valid. */
> +            ok = check_s2_startlevel(cpu, va_size == 64, level,
> +                                     inputsize, stride, pamax);
> +        }
>          if (!ok) {
>              /* AArch64 reports these as level 0 faults.
>               * AArch32 reports these as level 1 faults.

I'm not a fan of the ok = true / ok = false / ok =
check_s2_start_level() / if (!ok) ping-pong here as it is hard to
follow. I'm not sure how you could make it cleaner to follow though.
Maybe something like:

        /* For stage 2 translations the starting level is specified by the
         * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
         */
        int startlevel = extract32(tcr->raw_tcr, 6, 2);
        unsigned int pamax = arm_pamax(cpu);
        bool is_aarch64_regime = (va_size == 64);
        bool ok;

        if (va_size == 32 || stride == 9) {
            /* AArch32 or 4KB pages */
            level = 2 - startlevel;
        } else {
            /* 16KB or 64KB pages */
            level = 3 - startlevel;
        }

        if (is_aarch64_regime &&
            inputsize > pamax) {
            /* We have multiple choices but choose to fault.  */
            ok = false;
        } else {
            /* Check that the starting level is valid. */
            ok = check_s2_startlevel(cpu, is_aarch64_regime, level,
                                     inputsize, stride, pamax);
        }
        if (!ok) {
            /* AArch64 reports these as level 0 faults.
             * AArch32 reports these as level 1 faults.
             */
            level = is_aarch64_regime ? 0 : 1;
            fault_type = translation_fault;
            goto do_fault;
        }

But I'm wondering if it just makes more sense to push the:

    is_aarch64_regime && inputsize > pamax

Check into check_s2_startlevel? Then you could just have a simple call
which succeeds or falls through to a fault?

        /* Check that the starting level is valid. */
        if (!check_s2_startlevel(cpu, is_aarch64_regime, level,
                                     inputsize, stride, pamax) ){
            /* AArch64 reports these as level 0 faults.
             * AArch32 reports these as level 1 faults.
             */
            level = is_aarch64_regime ? 0 : 1;
            fault_type = translation_fault;
            goto do_fault;
        }

--
Alex Bennée

Re: [Qemu-devel] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check

[Edgar E. Iglesias]

On Fri, Jan 22, 2016 at 10:28:43AM +0000, Alex Bennée wrote:
> 
> Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:
> 
> > From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
> >
> > Implement the inputsize > pamax check for Stage 2 translations.
> > We have multiple choices for how to respond to errors and
> > choose to fault.
> >
> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> > ---
> >  target-arm/helper.c | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/target-arm/helper.c b/target-arm/helper.c
> > index 4abeb4d..9a7ff5e 100644
> > --- a/target-arm/helper.c
> > +++ b/target-arm/helper.c
> > @@ -6808,7 +6808,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >           */
> >          int startlevel = extract32(tcr->raw_tcr, 6, 2);
> >          unsigned int pamax = arm_pamax(cpu);
> > -        bool ok;
> > +        bool ok = true;
> >
> >          if (va_size == 32 || stride == 9) {
> >              /* AArch32 or 4KB pages */
> > @@ -6818,9 +6818,17 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >              level = 3 - startlevel;
> >          }
> >
> > -        /* Check that the starting level is valid. */
> > -        ok = check_s2_startlevel(cpu, va_size == 64, level,
> > -                                 inputsize, stride, pamax);
> > +        if (va_size == 64 &&
> > +            inputsize > pamax &&
> > +            (arm_el_is_aa64(env, 1) || inputsize > 40)) {
> 
> If va_size == 64 doesn't that imply arm_el_is_aa64(env, 1)? Looking
> further up the function it seems that is what sets va_size in the first
> place. I think that makes the inputsize > 40 check redundant.

va_size == 64 is true if the EL corresponding to the translation _regime_
is in 64 bit mode (in this case EL2).

EL1 may very well be in 32bit mode.


> 
> > +            /* We have multiple choices but choose to fault.  */
> > +            ok = false;
> > +        }
> > +        if (ok) {
> > +            /* Check that the starting level is valid. */
> > +            ok = check_s2_startlevel(cpu, va_size == 64, level,
> > +                                     inputsize, stride, pamax);
> > +        }
> >          if (!ok) {
> >              /* AArch64 reports these as level 0 faults.
> >               * AArch32 reports these as level 1 faults.
> 
> I'm not a fan of the ok = true / ok = false / ok =
> check_s2_start_level() / if (!ok) ping-pong here as it is hard to
> follow. I'm not sure how you could make it cleaner to follow though.
> Maybe something like:
> 
>         /* For stage 2 translations the starting level is specified by the
>          * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
>          */
>         int startlevel = extract32(tcr->raw_tcr, 6, 2);
>         unsigned int pamax = arm_pamax(cpu);
>         bool is_aarch64_regime = (va_size == 64);
>         bool ok;
> 
>         if (va_size == 32 || stride == 9) {
>             /* AArch32 or 4KB pages */
>             level = 2 - startlevel;
>         } else {
>             /* 16KB or 64KB pages */
>             level = 3 - startlevel;
>         }
> 
>         if (is_aarch64_regime &&
>             inputsize > pamax) {
>             /* We have multiple choices but choose to fault.  */
>             ok = false;
>         } else {
>             /* Check that the starting level is valid. */
>             ok = check_s2_startlevel(cpu, is_aarch64_regime, level,
>                                      inputsize, stride, pamax);
>         }
>         if (!ok) {
>             /* AArch64 reports these as level 0 faults.
>              * AArch32 reports these as level 1 faults.
>              */
>             level = is_aarch64_regime ? 0 : 1;
>             fault_type = translation_fault;
>             goto do_fault;
>         }
> 
> But I'm wondering if it just makes more sense to push the:
> 
>     is_aarch64_regime && inputsize > pamax
> 
> Check into check_s2_startlevel? Then you could just have a simple call
> which succeeds or falls through to a fault?

Yeah, I guess we could rename check_s2_startlevel to something more generic
and move all the checks there. I don't feel very strongly about either way...

Thanks,
Edgar



> 
>         /* Check that the starting level is valid. */
>         if (!check_s2_startlevel(cpu, is_aarch64_regime, level,
>                                      inputsize, stride, pamax) ){
>             /* AArch64 reports these as level 0 faults.
>              * AArch32 reports these as level 1 faults.
>              */
>             level = is_aarch64_regime ? 0 : 1;
>             fault_type = translation_fault;
>             goto do_fault;
>         }
> 
> --
> Alex Bennée

Re: [Qemu-devel] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check

[Alex Bennée]

Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:

> On Fri, Jan 22, 2016 at 10:28:43AM +0000, Alex Bennée wrote:
>>
>> Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:
>>
>> > From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>> >
>> > Implement the inputsize > pamax check for Stage 2 translations.
>> > We have multiple choices for how to respond to errors and
>> > choose to fault.
>> >
>> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
>> > ---
>> >  target-arm/helper.c | 16 ++++++++++++----
>> >  1 file changed, 12 insertions(+), 4 deletions(-)
>> >
>> > diff --git a/target-arm/helper.c b/target-arm/helper.c
>> > index 4abeb4d..9a7ff5e 100644
>> > --- a/target-arm/helper.c
>> > +++ b/target-arm/helper.c
>> > @@ -6808,7 +6808,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>> >           */
>> >          int startlevel = extract32(tcr->raw_tcr, 6, 2);
>> >          unsigned int pamax = arm_pamax(cpu);
>> > -        bool ok;
>> > +        bool ok = true;
>> >
>> >          if (va_size == 32 || stride == 9) {
>> >              /* AArch32 or 4KB pages */
>> > @@ -6818,9 +6818,17 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
>> >              level = 3 - startlevel;
>> >          }
>> >
>> > -        /* Check that the starting level is valid. */
>> > -        ok = check_s2_startlevel(cpu, va_size == 64, level,
>> > -                                 inputsize, stride, pamax);
>> > +        if (va_size == 64 &&
>> > +            inputsize > pamax &&
>> > +            (arm_el_is_aa64(env, 1) || inputsize > 40)) {
>>
>> If va_size == 64 doesn't that imply arm_el_is_aa64(env, 1)? Looking
>> further up the function it seems that is what sets va_size in the first
>> place. I think that makes the inputsize > 40 check redundant.
>
> va_size == 64 is true if the EL corresponding to the translation _regime_
> is in 64 bit mode (in this case EL2).
>
> EL1 may very well be in 32bit mode.

Ahh yes, I missed that on the first reading. I think it might be clearer
when reading the code to have the:

    bool is_aarch64_regime = (va_size == 64);

And use that to make it clear. And then comment on later check that it's
incompatible with EL1 being aarch32.

>
>>
>> > +            /* We have multiple choices but choose to fault.  */
>> > +            ok = false;
>> > +        }
>> > +        if (ok) {
>> > +            /* Check that the starting level is valid. */
>> > +            ok = check_s2_startlevel(cpu, va_size == 64, level,
>> > +                                     inputsize, stride, pamax);
>> > +        }
>> >          if (!ok) {
>> >              /* AArch64 reports these as level 0 faults.
>> >               * AArch32 reports these as level 1 faults.
>>
>> I'm not a fan of the ok = true / ok = false / ok =
>> check_s2_start_level() / if (!ok) ping-pong here as it is hard to
>> follow. I'm not sure how you could make it cleaner to follow though.
>> Maybe something like:
>>
>>         /* For stage 2 translations the starting level is specified by the
>>          * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
>>          */
>>         int startlevel = extract32(tcr->raw_tcr, 6, 2);
>>         unsigned int pamax = arm_pamax(cpu);
>>         bool is_aarch64_regime = (va_size == 64);
>>         bool ok;
>>
>>         if (va_size == 32 || stride == 9) {
>>             /* AArch32 or 4KB pages */
>>             level = 2 - startlevel;
>>         } else {
>>             /* 16KB or 64KB pages */
>>             level = 3 - startlevel;
>>         }
>>
>>         if (is_aarch64_regime &&
>>             inputsize > pamax) {
>>             /* We have multiple choices but choose to fault.  */
>>             ok = false;
>>         } else {
>>             /* Check that the starting level is valid. */
>>             ok = check_s2_startlevel(cpu, is_aarch64_regime, level,
>>                                      inputsize, stride, pamax);
>>         }
>>         if (!ok) {
>>             /* AArch64 reports these as level 0 faults.
>>              * AArch32 reports these as level 1 faults.
>>              */
>>             level = is_aarch64_regime ? 0 : 1;
>>             fault_type = translation_fault;
>>             goto do_fault;
>>         }
>>
>> But I'm wondering if it just makes more sense to push the:
>>
>>     is_aarch64_regime && inputsize > pamax
>>
>> Check into check_s2_startlevel? Then you could just have a simple call
>> which succeeds or falls through to a fault?
>
> Yeah, I guess we could rename check_s2_startlevel to something more generic
> and move all the checks there. I don't feel very strongly about either way...

I think it would be cleaner to follow. get_phys_addr_lpae is already a
bit of a monster so the less conditions to keep track of while reading
it the better IMHO.

> Thanks,
> Edgar
>
>
>
>>
>>         /* Check that the starting level is valid. */
>>         if (!check_s2_startlevel(cpu, is_aarch64_regime, level,
>>                                      inputsize, stride, pamax) ){
>>             /* AArch64 reports these as level 0 faults.
>>              * AArch32 reports these as level 1 faults.
>>              */
>>             level = is_aarch64_regime ? 0 : 1;
>>             fault_type = translation_fault;
>>             goto do_fault;
>>         }
>>
>> --
>> Alex Bennée


--
Alex Bennée

Re: [Qemu-devel] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check

[Edgar E. Iglesias]

On Fri, Jan 22, 2016 at 11:45:57AM +0000, Alex Bennée wrote:
> 
> Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:
> 
> > On Fri, Jan 22, 2016 at 10:28:43AM +0000, Alex Bennée wrote:
> >>
> >> Edgar E. Iglesias <edgar.iglesias@gmail.com> writes:
> >>
> >> > From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
> >> >
> >> > Implement the inputsize > pamax check for Stage 2 translations.
> >> > We have multiple choices for how to respond to errors and
> >> > choose to fault.
> >> >
> >> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> >> > ---
> >> >  target-arm/helper.c | 16 ++++++++++++----
> >> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >> >
> >> > diff --git a/target-arm/helper.c b/target-arm/helper.c
> >> > index 4abeb4d..9a7ff5e 100644
> >> > --- a/target-arm/helper.c
> >> > +++ b/target-arm/helper.c
> >> > @@ -6808,7 +6808,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >> >           */
> >> >          int startlevel = extract32(tcr->raw_tcr, 6, 2);
> >> >          unsigned int pamax = arm_pamax(cpu);
> >> > -        bool ok;
> >> > +        bool ok = true;
> >> >
> >> >          if (va_size == 32 || stride == 9) {
> >> >              /* AArch32 or 4KB pages */
> >> > @@ -6818,9 +6818,17 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >> >              level = 3 - startlevel;
> >> >          }
> >> >
> >> > -        /* Check that the starting level is valid. */
> >> > -        ok = check_s2_startlevel(cpu, va_size == 64, level,
> >> > -                                 inputsize, stride, pamax);
> >> > +        if (va_size == 64 &&
> >> > +            inputsize > pamax &&
> >> > +            (arm_el_is_aa64(env, 1) || inputsize > 40)) {
> >>
> >> If va_size == 64 doesn't that imply arm_el_is_aa64(env, 1)? Looking
> >> further up the function it seems that is what sets va_size in the first
> >> place. I think that makes the inputsize > 40 check redundant.
> >
> > va_size == 64 is true if the EL corresponding to the translation _regime_
> > is in 64 bit mode (in this case EL2).
> >
> > EL1 may very well be in 32bit mode.
> 
> Ahh yes, I missed that on the first reading. I think it might be clearer
> when reading the code to have the:
> 
>     bool is_aarch64_regime = (va_size == 64);
> 
> And use that to make it clear. And then comment on later check that it's
> incompatible with EL1 being aarch32.
> 
> >
> >>
> >> > +            /* We have multiple choices but choose to fault.  */
> >> > +            ok = false;
> >> > +        }
> >> > +        if (ok) {
> >> > +            /* Check that the starting level is valid. */
> >> > +            ok = check_s2_startlevel(cpu, va_size == 64, level,
> >> > +                                     inputsize, stride, pamax);
> >> > +        }
> >> >          if (!ok) {
> >> >              /* AArch64 reports these as level 0 faults.
> >> >               * AArch32 reports these as level 1 faults.
> >>
> >> I'm not a fan of the ok = true / ok = false / ok =
> >> check_s2_start_level() / if (!ok) ping-pong here as it is hard to
> >> follow. I'm not sure how you could make it cleaner to follow though.
> >> Maybe something like:
> >>
> >>         /* For stage 2 translations the starting level is specified by the
> >>          * VTCR_EL2.SL0 field (whose interpretation depends on the page size)
> >>          */
> >>         int startlevel = extract32(tcr->raw_tcr, 6, 2);
> >>         unsigned int pamax = arm_pamax(cpu);
> >>         bool is_aarch64_regime = (va_size == 64);
> >>         bool ok;
> >>
> >>         if (va_size == 32 || stride == 9) {
> >>             /* AArch32 or 4KB pages */
> >>             level = 2 - startlevel;
> >>         } else {
> >>             /* 16KB or 64KB pages */
> >>             level = 3 - startlevel;
> >>         }
> >>
> >>         if (is_aarch64_regime &&
> >>             inputsize > pamax) {
> >>             /* We have multiple choices but choose to fault.  */
> >>             ok = false;
> >>         } else {
> >>             /* Check that the starting level is valid. */
> >>             ok = check_s2_startlevel(cpu, is_aarch64_regime, level,
> >>                                      inputsize, stride, pamax);
> >>         }
> >>         if (!ok) {
> >>             /* AArch64 reports these as level 0 faults.
> >>              * AArch32 reports these as level 1 faults.
> >>              */
> >>             level = is_aarch64_regime ? 0 : 1;
> >>             fault_type = translation_fault;
> >>             goto do_fault;
> >>         }
> >>
> >> But I'm wondering if it just makes more sense to push the:
> >>
> >>     is_aarch64_regime && inputsize > pamax
> >>
> >> Check into check_s2_startlevel? Then you could just have a simple call
> >> which succeeds or falls through to a fault?
> >
> > Yeah, I guess we could rename check_s2_startlevel to something more generic
> > and move all the checks there. I don't feel very strongly about either way...
> 
> I think it would be cleaner to follow. get_phys_addr_lpae is already a
> bit of a monster so the less conditions to keep track of while reading
> it the better IMHO.


OK, I'll have a look at that for v4.

Thanks!
Edgar


> 
> > Thanks,
> > Edgar
> >
> >
> >
> >>
> >>         /* Check that the starting level is valid. */
> >>         if (!check_s2_startlevel(cpu, is_aarch64_regime, level,
> >>                                      inputsize, stride, pamax) ){
> >>             /* AArch64 reports these as level 0 faults.
> >>              * AArch32 reports these as level 1 faults.
> >>              */
> >>             level = is_aarch64_regime ? 0 : 1;
> >>             fault_type = translation_fault;
> >>             goto do_fault;
> >>         }
> >>
> >> --
> >> Alex Bennée
> 
> 
> --
> Alex Bennée