Re: [PATCH v14 09/13] x86/mm: global ASID process exit helpers

[Borislav Petkov <bp@alien8.de>]

On Sun, Mar 02, 2025 at 08:53:10AM -0500, Rik van Riel wrote:
> I've been there. Repeatedly :)

Yap, it is. And despite all the compile-time disabling fun, clang still can't
do proper DCE and complains about the inline asm in __invlpgb() using a u64 on
32-bit builds.

So I did the fix below, ontop and with that randconfig builds all pass fine.

What I have so far is here:

https://web.git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git/log/?h=tip-x86-cpu-tlbi

Lemme go through the rest of your patches now.

Thx.

diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h
index 5375145eb959..04f2c6f4cee3 100644
--- a/arch/x86/include/asm/tlb.h
+++ b/arch/x86/include/asm/tlb.h
@@ -29,6 +29,7 @@ static inline void invlpg(unsigned long addr)
 }
 
 
+#ifdef CONFIG_BROADCAST_TLB_FLUSH
 /*
  * INVLPGB does broadcast TLB invalidation across all the CPUs in the system.
  *
@@ -74,6 +75,14 @@ static inline void __tlbsync(void)
 	/* TLBSYNC: supported in binutils >= 0.36. */
 	asm volatile(".byte 0x0f, 0x01, 0xff" ::: "memory");
 }
+#else
+/* Some compilers simply can't do DCE */
+static inline void __invlpgb(unsigned long asid, unsigned long pcid,
+			     unsigned long addr, u16 nr_pages,
+			     bool pmd_stride, u8 flags) { }
+
+static inline void __tlbsync(void) { }
+#endif
 
 /*
  * INVLPGB can be targeted by virtual address, PCID, ASID, or any combination


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette