[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-arm] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-arm] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check |
Date: |
Fri, 22 Jan 2016 12:16:01 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Jan 22, 2016 at 10:28:43AM +0000, Alex Bennée wrote:
>
> Edgar E. Iglesias <address@hidden> writes:
>
> > From: "Edgar E. Iglesias" <address@hidden>
> >
> > 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 <address@hidden>
> > ---
> > 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
[Qemu-arm] [PATCH v2 2/3] target-arm: Make pamax an argument to check_s2_startlevel, Edgar E. Iglesias, 2016/01/21