x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 172 insertions, 0 deletions

diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs
new file mode 100644
index 000000000..ae20ed676
--- /dev/null
+++ b/rust/macros/kunit.rs
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Procedural macro to run KUnit tests using a user-space like syntax.
+//!
+//! Copyright (c) 2023 José Expósito <jose.exposito89@gmail.com>
+
+use std::ffi::CString;
+
+use proc_macro2::TokenStream;
+use quote::{
+    format_ident,
+    quote,
+    ToTokens, //
+};
+use syn::{
+    parse_quote,
+    Error,
+    Ident,
+    Item,
+    ItemMod,
+    LitCStr,
+    Result, //
+};
+
+pub(crate) fn kunit_tests(test_suite: Ident, mut module: ItemMod) -> Result<TokenStream> {
+    if test_suite.to_string().len() > 255 {
+        return Err(Error::new_spanned(
+            test_suite,
+            "test suite names cannot exceed the maximum length of 255 bytes",
+        ));
+    }
+
+    // We cannot handle modules that defer to another file (e.g. `mod foo;`).
+    let Some((module_brace, module_items)) = module.content.take() else {
+        Err(Error::new_spanned(
+            module,
+            "`#[kunit_tests(test_name)]` attribute should only be applied to inline modules",
+        ))?
+    };
+
+    // Make the entire module gated behind `CONFIG_KUNIT`.
+    module
+        .attrs
+        .insert(0, parse_quote!(#[cfg(CONFIG_KUNIT="y")]));
+
+    let mut processed_items = Vec::new();
+    let mut test_cases = Vec::new();
+
+    // Generate the test KUnit test suite and a test case for each `#[test]`.
+    //
+    // The code generated for the following test module:
+    //
+    // ```
+    // #[kunit_tests(kunit_test_suit_name)]
+    // mod tests {
+    //     #[test]
+    //     fn foo() {
+    //         assert_eq!(1, 1);
+    //     }
+    //
+    //     #[test]
+    //     fn bar() {
+    //         assert_eq!(2, 2);
+    //     }
+    // }
+    // ```
+    //
+    // Looks like:
+    //
+    // ```
+    // unsafe extern "C" fn kunit_rust_wrapper_foo(_test: *mut ::kernel::bindings::kunit) { foo(); }
+    // unsafe extern "C" fn kunit_rust_wrapper_bar(_test: *mut ::kernel::bindings::kunit) { bar(); }
+    //
+    // static mut TEST_CASES: [::kernel::bindings::kunit_case; 3] = [
+    //     ::kernel::kunit::kunit_case(c"foo", kunit_rust_wrapper_foo),
+    //     ::kernel::kunit::kunit_case(c"bar", kunit_rust_wrapper_bar),
+    //     ::pin_init::zeroed(),
+    // ];
+    //
+    // ::kernel::kunit_unsafe_test_suite!(kunit_test_suit_name, TEST_CASES);
+    // ```
+    //
+    // Non-function items (e.g. imports) are preserved.
+    for item in module_items {
+        let Item::Fn(mut f) = item else {
+            processed_items.push(item);
+            continue;
+        };
+
+        if f.attrs
+            .extract_if(.., |attr| attr.path().is_ident("test"))
+            .count()
+            == 0
+        {
+            processed_items.push(Item::Fn(f));
+            continue;
+        }
+
+        let test = f.sig.ident.clone();
+
+        // Retrieve `#[cfg]` applied on the function which needs to be present on derived items too.
+        let cfg_attrs: Vec<_> = f
+            .attrs
+            .iter()
+            .filter(|attr| attr.path().is_ident("cfg"))
+            .cloned()
+            .collect();
+
+        // Before the test, override usual `assert!` and `assert_eq!` macros with ones that call
+        // KUnit instead.
+        let test_str = test.to_string();
+        let path = CString::new(crate::helpers::file()).expect("file path cannot contain NUL");
+        processed_items.push(parse_quote! {
+            #[allow(unused)]
+            macro_rules! assert {
+                ($cond:expr $(,)?) => {{
+                    kernel::kunit_assert!(#test_str, #path, 0, $cond);
+                }}
+            }
+        });
+        processed_items.push(parse_quote! {
+            #[allow(unused)]
+            macro_rules! assert_eq {
+                ($left:expr, $right:expr $(,)?) => {{
+                    kernel::kunit_assert_eq!(#test_str, #path, 0, $left, $right);
+                }}
+            }
+        });
+
+        // Add back the test item.
+        processed_items.push(Item::Fn(f));
+
+        let kunit_wrapper_fn_name = format_ident!("kunit_rust_wrapper_{test}");
+        let test_cstr = LitCStr::new(
+            &CString::new(test_str.as_str()).expect("identifier cannot contain NUL"),
+            test.span(),
+        );
+        processed_items.push(parse_quote! {
+            unsafe extern "C" fn #kunit_wrapper_fn_name(_test: *mut ::kernel::bindings::kunit) {
+                (*_test).status = ::kernel::bindings::kunit_status_KUNIT_SKIPPED;
+
+                // Append any `cfg` attributes the user might have written on their tests so we
+                // don't attempt to call them when they are `cfg`'d out. An extra `use` is used
+                // here to reduce the length of the assert message.
+                #(#cfg_attrs)*
+                {
+                    (*_test).status = ::kernel::bindings::kunit_status_KUNIT_SUCCESS;
+                    use ::kernel::kunit::is_test_result_ok;
+                    assert!(is_test_result_ok(#test()));
+                }
+            }
+        });
+
+        test_cases.push(quote!(
+            ::kernel::kunit::kunit_case(#test_cstr, #kunit_wrapper_fn_name)
+        ));
+    }
+
+    let num_tests_plus_1 = test_cases.len() + 1;
+    processed_items.push(parse_quote! {
+        static mut TEST_CASES: [::kernel::bindings::kunit_case; #num_tests_plus_1] = [
+            #(#test_cases,)*
+            ::pin_init::zeroed(),
+        ];
+    });
+    processed_items.push(parse_quote! {
+        ::kernel::kunit_unsafe_test_suite!(#test_suite, TEST_CASES);
+    });
+
+    module.content = Some((module_brace, processed_items));
+    Ok(module.to_token_stream())
+}