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Message-ID: <6cc43cd3-5f67-49cf-bafb-67a0a22368cf@nvidia.com>
Date: Mon, 6 Oct 2025 15:38:06 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: Alexandre Courbot <acourbot@...dia.com>, linux-kernel@...r.kernel.org,
rust-for-linux@...r.kernel.org, dri-devel@...ts.freedesktop.org,
dakr@...nel.org
Cc: Alistair Popple <apopple@...dia.com>, Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
Gary Guo <gary@...yguo.net>, bjorn3_gh@...tonmail.com,
Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
John Hubbard <jhubbard@...dia.com>, Timur Tabi <ttabi@...dia.com>,
joel@...lfernandes.org, Elle Rhumsaa <elle@...thered-steel.dev>,
Yury Norov <yury.norov@...il.com>,
Daniel Almeida <daniel.almeida@...labora.com>,
Andrea Righi <arighi@...dia.com>, nouveau@...ts.freedesktop.org
Subject: Re: [PATCH v6 5/5] rust: bitfield: Add KUNIT tests for bitfield
On 10/6/2025 6:37 AM, Alexandre Courbot wrote:
> On Sat Oct 4, 2025 at 12:47 AM JST, Joel Fernandes wrote:
>> Add KUNIT tests to make sure the macro is working correctly.
>>
>> Reviewed-by: Alexandre Courbot <acourbot@...dia.com>
>> Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
>> ---
>> rust/kernel/bitfield.rs | 323 ++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 323 insertions(+)
>>
>> diff --git a/rust/kernel/bitfield.rs b/rust/kernel/bitfield.rs
>> index 09cd5741598c..f0e341a1a979 100644
>> --- a/rust/kernel/bitfield.rs
>> +++ b/rust/kernel/bitfield.rs
>> @@ -329,3 +329,326 @@ fn default() -> Self {
>> }
>> };
>> }
>> +
>> +#[::kernel::macros::kunit_tests(kernel_bitfield)]
>> +mod tests {
>> + use core::convert::TryFrom;
>> +
>> + // Enum types for testing => and ?=> conversions
>> + #[derive(Debug, Default, Clone, Copy, PartialEq)]
>> + enum MemoryType {
>> + #[default]
>> + Unmapped = 0,
>> + Normal = 1,
>> + Device = 2,
>> + Reserved = 3,
>> + }
>> +
>> + impl TryFrom<u8> for MemoryType {
>> + type Error = u8;
>> + fn try_from(value: u8) -> Result<Self, Self::Error> {
>> + match value {
>> + 0 => Ok(MemoryType::Unmapped),
>> + 1 => Ok(MemoryType::Normal),
>> + 2 => Ok(MemoryType::Device),
>> + 3 => Ok(MemoryType::Reserved),
>> + _ => Err(value),
>> + }
>> + }
>> + }
>> +
>> + impl From<MemoryType> for u64 {
>> + fn from(mt: MemoryType) -> u64 {
>> + mt as u64
>> + }
>> + }
>> +
>> + #[derive(Debug, Default, Clone, Copy, PartialEq)]
>> + enum Priority {
>> + #[default]
>> + Low = 0,
>> + Medium = 1,
>> + High = 2,
>> + Critical = 3,
>> + }
>> +
>> + impl From<u8> for Priority {
>> + fn from(value: u8) -> Self {
>> + match value & 0x3 {
>> + 0 => Priority::Low,
>> + 1 => Priority::Medium,
>> + 2 => Priority::High,
>> + _ => Priority::Critical,
>> + }
>> + }
>> + }
>> +
>> + impl From<Priority> for u16 {
>> + fn from(p: Priority) -> u16 {
>> + p as u16
>> + }
>> + }
>> +
>> + bitfield! {
>> + struct TestPageTableEntry(u64) {
>> + 0:0 present as bool;
>> + 1:1 writable as bool;
>> + 11:9 available as u8;
>> + 13:12 mem_type as u8 ?=> MemoryType;
>> + 17:14 extended_type as u8 ?=> MemoryType; // For testing failures
>> + 51:12 pfn as u64;
>
> Is the overlap with `mem_type` and `extended_type` on purpose?
Yes, here I was testing the failure mode of ?=> without having to introduce a
new enum type. But I could just do so with mem_type by adding more bits to it,
so I'll do that and remove extended_type.
> It looks strange to me that the PFN also includes the memory type.
I agree with this (even though these structs are just approximately accurate and
for testing purposes). Since we're testing overlap already in later tests, I
will just remove it from this test.
Following is the new struct now, hope it looks ok:
bitfield! {
struct TestPageTableEntry(u64) {
0:0 present as bool;
1:1 writable as bool;
11:9 available as u8;
15:12 mem_type as u8 ?=> MemoryType;
51:16 pfn as u64;
61:52 available2 as u16;
}
}
>> + 51:12 pfn_overlap as u64;
>
> If `pfn` needs to be adjusted then I guess this one also needs to be.
>
>> + 61:52 available2 as u16;
>> + }
>> + }
>> +
>> + bitfield! {
>> + struct TestControlRegister(u16) {
>> + 0:0 enable as bool;
>> + 3:1 mode as u8;
>> + 5:4 priority as u8 => Priority;
>> + 7:4 priority_nibble as u8;
>> + 15:8 channel as u8;
>> + }
>> + }
>> +
>> + bitfield! {
>> + struct TestStatusRegister(u8) {
>> + 0:0 ready as bool;
>> + 1:1 error as bool;
>> + 3:2 state as u8;
>> + 7:4 reserved as u8;
>> + 7:0 full_byte as u8; // For entire register
>> + }
>> + }
>> +
>> + #[test]
>> + fn test_single_bits() {
>> + let mut pte = TestPageTableEntry::default();
>> +
>> + assert!(!pte.present());
>> + assert!(!pte.writable());
>> + assert_eq!(u64::from(pte), 0x0);
>> +
>> + pte = pte.set_present(true);
>> + assert!(pte.present());
>> + assert_eq!(u64::from(pte), 0x1);
>> +
>> + pte = pte.set_writable(true);
>> + assert!(pte.writable());
>> + assert_eq!(u64::from(pte), 0x3);
>> +
>> + pte = pte.set_writable(false);
>> + assert!(!pte.writable());
>> + assert_eq!(u64::from(pte), 0x1);
>> +
>> + assert_eq!(pte.available(), 0);
>> + pte = pte.set_available(0x5);
>> + assert_eq!(pte.available(), 0x5);
>> + assert_eq!(u64::from(pte), 0xA01);
>> + }
>> +
>> + #[test]
>> + fn test_range_fields() {
>> + let mut pte = TestPageTableEntry::default();
>> + assert_eq!(u64::from(pte), 0x0);
>> +
>> + pte = pte.set_pfn(0x123456);
>> + assert_eq!(pte.pfn(), 0x123456);
>> + // Test overlapping field reads same value
>> + assert_eq!(pte.pfn_overlap(), 0x123456);
>> + assert_eq!(u64::from(pte), 0x123456000);
>> +
>> + pte = pte.set_available(0x7);
>> + assert_eq!(pte.available(), 0x7);
>> + assert_eq!(u64::from(pte), 0x123456E00);
>> +
>> + pte = pte.set_available2(0x3FF);
>> + assert_eq!(pte.available2(), 0x3FF);
>> + assert_eq!(u64::from(pte), 0x3FF0000123456E00);
>> +
>> + // Test TryFrom with ?=> for MemoryType
>> + pte = pte.set_mem_type(MemoryType::Device);
>> + assert_eq!(pte.mem_type(), Ok(MemoryType::Device));
>> + assert_eq!(u64::from(pte), 0x3FF0000123456E00);
>> +
>> + pte = pte.set_mem_type(MemoryType::Normal);
>> + assert_eq!(pte.mem_type(), Ok(MemoryType::Normal));
>> + assert_eq!(u64::from(pte), 0x3FF0000123455E00);
>> +
>> + // Test all valid values for mem_type
>> + pte = pte.set_mem_type(MemoryType::Reserved);
>> + assert_eq!(pte.mem_type(), Ok(MemoryType::Reserved));
>> + assert_eq!(u64::from(pte), 0x3FF0000123457E00);
>> +
>> + // Test failure case using extended_type field which has 4 bits (0-15)
>> + // MemoryType only handles 0-3, so values 4-15 should return Err
>> + let mut raw = pte.into();
>> + // Set bits 17:14 to 7 (invalid for MemoryType)
>> + raw = (raw & !::kernel::bits::genmask_u64(14..=17)) | (0x7 << 14);
>> + let invalid_pte = TestPageTableEntry(raw);
>> + // Should return Err with the invalid value
>> + assert_eq!(invalid_pte.extended_type(), Err(0x7));
>> +
>> + // Test a valid value after testing invalid to ensure both cases work
>> + // Set bits 17:14 to 2 (valid: Device)
>> + raw = (raw & !::kernel::bits::genmask_u64(14..=17)) | (0x2 << 14);
>> + let valid_pte = TestPageTableEntry(raw);
>> + assert_eq!(valid_pte.extended_type(), Ok(MemoryType::Device));
>> +
>> + let max_pfn = ::kernel::bits::genmask_u64(0..=39);
>> + pte = pte.set_pfn(max_pfn);
>> + assert_eq!(pte.pfn(), max_pfn);
>> + assert_eq!(pte.pfn_overlap(), max_pfn);
>> + }
>> +
>> + #[test]
>> + fn test_builder_pattern() {
>> + let pte = TestPageTableEntry::default()
>> + .set_present(true)
>> + .set_writable(true)
>> + .set_available(0x7)
>> + .set_pfn(0xABCDEF)
>> + .set_mem_type(MemoryType::Reserved)
>> + .set_available2(0x3FF);
>> +
>> + assert!(pte.present());
>> + assert!(pte.writable());
>> + assert_eq!(pte.available(), 0x7);
>> + assert_eq!(pte.pfn(), 0xABCDEF);
>> + assert_eq!(pte.pfn_overlap(), 0xABCDEF);
>> + assert_eq!(pte.mem_type(), Ok(MemoryType::Reserved));
>> + assert_eq!(pte.available2(), 0x3FF);
>
> Maybe check the raw value here as well, although I guess the previous
> test already covered this anyway.
>
> With these points confirmed,
>
> Reviewed-by: Alexandre Courbot <acourbot@...dia.com>
Thanks! I will resend just this patch as a reply-to this patch (hope that's Ok).
- Joel
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