From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41167) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aMZhZ-0003J5-6u for qemu-devel@nongnu.org; Fri, 22 Jan 2016 06:16:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aMZhV-0002dd-SN for qemu-devel@nongnu.org; Fri, 22 Jan 2016 06:16:25 -0500 Date: Fri, 22 Jan 2016 12:16:01 +0100 From: "Edgar E. Iglesias" Message-ID: <20160122111601.GD25287@toto> References: <1453375108-25229-1-git-send-email-edgar.iglesias@gmail.com> <1453375108-25229-4-git-send-email-edgar.iglesias@gmail.com> <8737tpj4bo.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8737tpj4bo.fsf@linaro.org> Subject: Re: [Qemu-devel] [PATCH v2 3/3] target-arm: Implement the S2 MMU inputsize > pamax check List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex =?iso-8859-1?Q?Benn=E9e?= Cc: edgar.iglesias@xilinx.com, peter.maydell@linaro.org, qemu-arm@nongnu.org, qemu-devel@nongnu.org On Fri, Jan 22, 2016 at 10:28:43AM +0000, Alex Bennée wrote: > > Edgar E. Iglesias writes: > > > From: "Edgar E. Iglesias" > > > > 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 > > --- > > 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