linux-kernel - Re: [PATCH v4 27/30] x86/tlb: Make __flush_tlb

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Message-ID: <Z4bWBUGUH34qLUt0@google.com>
Date: Tue, 14 Jan 2025 13:24:21 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Valentin Schneider <vschneid@...hat.com>
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Subject: Re: [PATCH v4 27/30] x86/tlb: Make __flush_tlb_local() noinstr-compliant

On Tue, Jan 14, 2025, Valentin Schneider wrote:
> Later patches will require issuing a __flush_tlb_all() from noinstr code.
> This requires making both __flush_tlb_local() and __flush_tlb_global()
> noinstr-compliant.
> 
> For __flush_tlb_local(), xen_flush_tlb() has already been made noinstr, so
> it's just native_flush_tlb_global(), and simply __always_inline'ing
> invalidate_user_asid() gets us there
> 
> Signed-off-by: Valentin Schneider <vschneid@...hat.com>
> ---

...

> @@ -1206,7 +1206,7 @@ STATIC_NOPV noinstr void native_flush_tlb_global(void)
>  /*
>   * Flush the entire current user mapping
>   */
> -STATIC_NOPV void native_flush_tlb_local(void)
> +STATIC_NOPV noinstr void native_flush_tlb_local(void)

native_write_cr3() and __native_read_cr3() need to be __always_inline.

vmlinux.o: warning: objtool: native_flush_tlb_local+0x8: call to __native_read_cr3() leaves .noinstr.text section