From: riel@xxxxxxxxxxx <riel@xxxxxxxxxxx> Sent: Sunday, January 12, 2025 7:54 AM
>
> Add invlpgb.h with the helper functions and definitions needed to use
> broadcast TLB invalidation on AMD EPYC 3 and newer CPUs.
>
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
> ---
> arch/x86/include/asm/invlpgb.h | 95 +++++++++++++++++++++++++++++++++
> arch/x86/include/asm/tlbflush.h | 1 +
> 2 files changed, 96 insertions(+)
> create mode 100644 arch/x86/include/asm/invlpgb.h
>
> diff --git a/arch/x86/include/asm/invlpgb.h b/arch/x86/include/asm/invlpgb.h
> new file mode 100644
> index 000000000000..d62e3733a1ab
> --- /dev/null
> +++ b/arch/x86/include/asm/invlpgb.h
> @@ -0,0 +1,95 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_INVLPGB
> +#define _ASM_X86_INVLPGB
> +
> +#include <vdso/bits.h>
> +
> +/*
> + * INVLPGB does broadcast TLB invalidation across all the CPUs in the system.
> + *
> + * The INVLPGB instruction is weakly ordered, and a batch of invalidations can
> + * be done in a parallel fashion.
> + *
> + * TLBSYNC is used to ensure that pending INVLPGB invalidations initiated from
> + * this CPU have completed.
> + */
> +static inline void __invlpgb(unsigned long asid, unsigned long pcid, unsigned long addr,
> + int extra_count, bool pmd_stride, unsigned long flags)
> +{
> + u32 edx = (pcid << 16) | asid;
> + u32 ecx = (pmd_stride << 31);
> + u64 rax = addr | flags;
> +
> + /* Protect against negative numbers. */
> + extra_count = max(extra_count, 0);
> + ecx |= extra_count;
> +
> + asm volatile("invlpgb" : : "a" (rax), "c" (ecx), "d" (edx));
The above needs to be:
asm volatile(".byte 0x0f, 0x01, 0xfe" : : "a" (rax), "c" (ecx), "d" (edx));
plus an explanatory comment.
As Boris Petkov previously noted[1], the "invlpgb" instruction name requires
binutils version 2.36. But the current Linux kernel minimum binutils version
is 2.25 (in scripts/min-tool-version.sh). For example, I'm using binutils 2.34,
and your asm statement doesn't compile.
> +}
> +
> +/* Wait for INVLPGB originated by this CPU to complete. */
> +static inline void tlbsync(void)
> +{
> + asm volatile("tlbsync");
Same as above for "tlbsync".
Michael
[1] https://lore.kernel.org/lkml/20250102124247.GPZ3aJx8JTJa6PcaOW@fat_crate.local/
