From: Johannes Berg <johannes.berg@xxxxxxxxx> [ Upstream commit fe5b391fc56f77cf3c22a9dd4f0ce20db0e3533f ] On 32-bit ARCH=um, CONFIG_X86_32 is still defined, so it doesn't indicate building on real X86 machines. There's no MSR on UML though, so add a check for CONFIG_X86. Reported-by: Arnd Bergmann <arnd@xxxxxxxx> Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> Link: https://lore.kernel.org/r/20250606090110.15784-2-johannes@xxxxxxxxxxxxxxxx Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- **YES** This commit should be backported to stable kernel trees for the following reasons: 1. **It fixes a build failure**: The commit addresses a build breakage on 32-bit UML (User Mode Linux) where `CONFIG_X86_32` is defined but MSR (Machine Specific Register) support is not available. This prevents successful compilation when building for 32-bit UML. 2. **The fix is minimal and contained**: The change is a simple one-line modification that adds an additional check for `CONFIG_X86` alongside the existing `CONFIG_X86_32` check. The change from: ```c #ifdef CONFIG_X86_32 ``` to: ```c #if defined(CONFIG_X86) && defined(CONFIG_X86_32) ``` This ensures MSR usage is only enabled on real x86 hardware, not on UML. 3. **Similar pattern to other backported fixes**: Looking at the similar commits, we see that: - Commit #1 (pata_cs5535 + UML) was backported (YES) - it added `depends on !UML` to prevent build issues - Commit #2 (dmaengine: idxd + UML) was backported (YES) - similar UML build fix These show a pattern where UML build fixes are considered important for stable backporting. 4. **No functional changes for normal users**: The fix only affects build configurations and doesn't change any runtime behavior for users running on actual x86 hardware. This minimizes regression risk. 5. **Prevents allyesconfig/allmodconfig breakage**: As seen in similar commits, UML build failures can break comprehensive kernel build tests (allyesconfig/allmodconfig), which are important for continuous integration and testing. 6. **The issue affects a subsystem driver**: While pata_cs5536 is a specific driver for older AMD CS5536 hardware, build failures in any driver can impact kernel testing infrastructure and distributions that build comprehensive kernel packages. The commit follows the stable tree rules by being a minimal, focused fix for an actual bug (build failure) with very low risk of introducing new issues. drivers/ata/pata_cs5536.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/ata/pata_cs5536.c b/drivers/ata/pata_cs5536.c index b811efd2cc346..73e81e160c91f 100644 --- a/drivers/ata/pata_cs5536.c +++ b/drivers/ata/pata_cs5536.c @@ -27,7 +27,7 @@ #include <scsi/scsi_host.h> #include <linux/dmi.h> -#ifdef CONFIG_X86_32 +#if defined(CONFIG_X86) && defined(CONFIG_X86_32) #include <asm/msr.h> static int use_msr; module_param_named(msr, use_msr, int, 0644); -- 2.39.5