Re: [PATCH v6 7/7] mm: allow page scrubbing routine(s) to be arch controlled

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.06.2025 15:02, Jan Beulich wrote:
> --- /dev/null
> +++ b/xen/arch/x86/scrub_page.S
> @@ -0,0 +1,39 @@
> +        .file __FILE__
> +
> +#include <asm/asm_defns.h>
> +#include <xen/page-size.h>
> +#include <xen/scrub.h>
> +
> +FUNC(scrub_page_cold)
> +        mov     $PAGE_SIZE/32, %ecx
> +        mov     $SCRUB_PATTERN, %rax
> +
> +0:      movnti  %rax,   (%rdi)
> +        movnti  %rax,  8(%rdi)
> +        movnti  %rax, 16(%rdi)
> +        movnti  %rax, 24(%rdi)
> +        add     $32, %rdi
> +        sub     $1, %ecx
> +        jnz     0b
> +
> +        sfence
> +        ret
> +END(scrub_page_cold)
> +
> +        .macro scrub_page_stosb
> +        mov     $PAGE_SIZE, %ecx
> +        mov     $SCRUB_BYTE_PATTERN, %eax
> +        rep stosb
> +        ret
> +        .endm
> +
> +        .macro scrub_page_stosq
> +        mov     $PAGE_SIZE/8, %ecx
> +        mov     $SCRUB_PATTERN, %rax
> +        rep stosq
> +        ret
> +        .endm
> +
> +FUNC(scrub_page_hot)
> +        ALTERNATIVE scrub_page_stosq, scrub_page_stosb, X86_FEATURE_ERMS
> +END(scrub_page_hot)

Bah, I've noticed only now that I failed to do the ret -> RET conversion here
during the most recent re-basing.

Jan