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Re: [PATCH 4/4] x86: Avoid using .byte for instructions where safe to do so
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 5 Jan 2026 16:58:46 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 05 Jan 2026 15:58:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 30.12.2025 14:54, Andrew Cooper wrote:
> --- a/xen/arch/x86/include/asm/asm-defns.h
> +++ b/xen/arch/x86/include/asm/asm-defns.h
> @@ -1,9 +1,5 @@
> #include <asm/page-bits.h>
>
> -.macro clzero
> - .byte 0x0f, 0x01, 0xfc
> -.endm
This can't go away yet, as it became known to gas only in 2.26.
> --- a/xen/arch/x86/include/asm/prot-key.h
> +++ b/xen/arch/x86/include/asm/prot-key.h
> @@ -19,16 +19,14 @@ static inline uint32_t rdpkru(void)
> {
> uint32_t pkru;
>
> - asm volatile ( ".byte 0x0f,0x01,0xee"
> - : "=a" (pkru) : "c" (0) : "dx" );
> + asm volatile ( "rdpkru" : "=a" (pkru) : "c" (0) : "dx" );
>
> return pkru;
> }
>
> static inline void wrpkru(uint32_t pkru)
> {
> - asm volatile ( ".byte 0x0f,0x01,0xef"
> - :: "a" (pkru), "d" (0), "c" (0) );
> + asm volatile ( "wrpkru" :: "a" (pkru), "d" (0), "c" (0) );
> }
Same for both of these.
Jan
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