[PATCH v2] arm64: cpufeature: Fix the visibility of compat hwcaps

[PATCH v2] arm64: cpufeature: Fix the visibility of compat hwcaps

[Amit Daniel Kachhap]

Commit 237405ebef58 ("arm64: cpufeature: Force HWCAP to be based on the
sysreg visible to user-space") forced the hwcaps to use sanitised
user-space view of the id registers. However, the ID register structures
used to select few compat cpufeatures (vfp, crc32, ...) are masked and
hence such hwcaps do not appear in /proc/cpuinfo anymore for PER_LINUX32
personality.

Add the ID register structures explicitly and set the relevant entry as
visible for compat hwcaps.

While at it, update the comment for structure ftr_generic_32bits[] which
lists the ID register that use it.

Fixes: 237405ebef58 ("arm64: cpufeature: Force HWCAP to be based on the sysreg visible to user-space")
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
Changes in v2:
*) Rebased to linux v6.1-rc3.
*) Modified comments for structure ftr_generic_32bits as pointed by
   James.
*) Sending this fix patch separately from the previous series
   (http://lists.infradead.org/pipermail/linux-arm-kernel/2022-October/784025.html).

 arch/arm64/kernel/cpufeature.c | 38 +++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6062454a9067..4132a24fd7d0 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -428,6 +428,30 @@ static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = {
 	ARM64_FTR_END,
 };
 
+static const struct arm64_ftr_bits ftr_mvfr0[] = {
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPROUND_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPSHVEC_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPSQRT_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPDIVIDE_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPTRAP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPDP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_FPSP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR0_SIMD_SHIFT, 4, 0),
+	ARM64_FTR_END,
+};
+
+static const struct arm64_ftr_bits ftr_mvfr1[] = {
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_SIMDFMAC_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_FPHP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_SIMDHP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_SIMDSP_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_SIMDINT_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_SIMDLS_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_FPDNAN_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR1_FPFTZ_SHIFT, 4, 0),
+	ARM64_FTR_END,
+};
+
 static const struct arm64_ftr_bits ftr_mvfr2[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR2_FPMISC_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, MVFR2_SIMDMISC_SHIFT, 4, 0),
@@ -458,10 +482,10 @@ static const struct arm64_ftr_bits ftr_id_isar0[] = {
 
 static const struct arm64_ftr_bits ftr_id_isar5[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_RDM_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_CRC32_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_SHA2_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_SHA1_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_AES_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_CRC32_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_SHA2_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_SHA1_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_AES_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR5_SEVL_SHIFT, 4, 0),
 	ARM64_FTR_END,
 };
@@ -574,7 +598,7 @@ static const struct arm64_ftr_bits ftr_smcr[] = {
  * Common ftr bits for a 32bit register with all hidden, strict
  * attributes, with 4bit feature fields and a default safe value of
  * 0. Covers the following 32bit registers:
- * id_isar[1-4], id_mmfr[1-3], id_pfr1, mvfr[0-1]
+ * id_isar[1-3], id_mmfr[1-3]
  */
 static const struct arm64_ftr_bits ftr_generic_32bits[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0),
@@ -645,8 +669,8 @@ static const struct __ftr_reg_entry {
 	ARM64_FTR_REG(SYS_ID_ISAR6_EL1, ftr_id_isar6),
 
 	/* Op1 = 0, CRn = 0, CRm = 3 */
-	ARM64_FTR_REG(SYS_MVFR0_EL1, ftr_generic_32bits),
-	ARM64_FTR_REG(SYS_MVFR1_EL1, ftr_generic_32bits),
+	ARM64_FTR_REG(SYS_MVFR0_EL1, ftr_mvfr0),
+	ARM64_FTR_REG(SYS_MVFR1_EL1, ftr_mvfr1),
 	ARM64_FTR_REG(SYS_MVFR2_EL1, ftr_mvfr2),
 	ARM64_FTR_REG(SYS_ID_PFR2_EL1, ftr_id_pfr2),
 	ARM64_FTR_REG(SYS_ID_DFR1_EL1, ftr_id_dfr1),
-- 
2.17.1


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Re: [PATCH v2] arm64: cpufeature: Fix the visibility of compat hwcaps

[Suzuki K Poulose]

Hi Amit

On 02/11/2022 10:21, Amit Daniel Kachhap wrote:
> Commit 237405ebef58 ("arm64: cpufeature: Force HWCAP to be based on the
> sysreg visible to user-space") forced the hwcaps to use sanitised
> user-space view of the id registers. However, the ID register structures
> used to select few compat cpufeatures (vfp, crc32, ...) are masked and
> hence such hwcaps do not appear in /proc/cpuinfo anymore for PER_LINUX32
> personality.
> 
> Add the ID register structures explicitly and set the relevant entry as
> visible for compat hwcaps.
> 
> While at it, update the comment for structure ftr_generic_32bits[] which
> lists the ID register that use it.
> 

Minor nit: With this change, we expose mvfr*_el1 and the following
document needs an update to reflect the change.

Documentation/arm64/cpu-feature-registers.rst

Otherwise, looks good to me.

Suzuki


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Re: [PATCH v2] arm64: cpufeature: Fix the visibility of compat hwcaps

[Amit Kachhap]

On 11/2/22 16:17, Suzuki K Poulose wrote:
> Hi Amit
> 
> On 02/11/2022 10:21, Amit Daniel Kachhap wrote:
>> Commit 237405ebef58 ("arm64: cpufeature: Force HWCAP to be based on the
>> sysreg visible to user-space") forced the hwcaps to use sanitised
>> user-space view of the id registers. However, the ID register structures
>> used to select few compat cpufeatures (vfp, crc32, ...) are masked and
>> hence such hwcaps do not appear in /proc/cpuinfo anymore for PER_LINUX32
>> personality.
>>
>> Add the ID register structures explicitly and set the relevant entry as
>> visible for compat hwcaps.
>>
>> While at it, update the comment for structure ftr_generic_32bits[] which
>> lists the ID register that use it.
>>
> 
> Minor nit: With this change, we expose mvfr*_el1 and the following
> document needs an update to reflect the change.
> 
> Documentation/arm64/cpu-feature-registers.rst

I just send the v3 with your suggestion. I missed changing the mrs
instruction emulation for crm argument in v2 which I did now.

> 
> Otherwise, looks good to me.

Thanks for your feedback.

Amit
> 
> Suzuki
> 

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