Re: [PATCH v2 11/20] arm64: entry: sdei: Restore all clobberable GPRs
Mark Rutland <[email protected]>
| Newsgroups | org.infradead.lists.linux-arm-kernel,org.kernel.vger.stable |
|---|---|
| Message-ID | <anXDGLkN-DbQ5hga@J2N7QTR9R3> |
On Tue, Aug 04, 2026 at 06:04:54PM +0100, Mark Rutland wrote:
> Currently __sdei_asm_handler() avoids restoring x20 to x27, as these are
> not be clobbered by existing code. This is correct today, but it makes
> it awkward to rework __sdei_asm_handler(). Given the rarity of SDEI
> events, restoring x20 to x27 should not have a measurable impact.
>
> Restore x20 to x27 when returning from an SDEI event handler. This will
> free up those GPRs for usage in __sdei_asm_handler() prior to return.
Sashiko noticed an error below that I'll fix for v3.
> - /* restore regs >x17 that we clobbered */
> + /* restore regs >x17 that firmware won't restore */
> mov x4, x19 // keep x4 for __sdei_asm_exit_trampoline
> - ldp x28, x29, [x4, #SDEI_EVENT_INTREGS + 16 * 14]
> ldp x18, x19, [x4, #SDEI_EVENT_INTREGS + 16 * 9]
> + ldp x20, x21, [x4, #SDEI_EVENT_INTREGS + 16 * 10]
> + ldp x22, x23, [x4, #SDEI_EVENT_INTREGS + 16 * 11]
> + ldp x24, x25, [x4, #SDEI_EVENT_INTREGS + 16 * 12]
> + ldp x22, x27, [x4, #SDEI_EVENT_INTREGS + 16 * 13]
^^^
That should be 'x26'.
Mark.
> + ldp x28, x29, [x4, #SDEI_EVENT_INTREGS + 16 * 14]
> ldp lr, x1, [x4, #SDEI_EVENT_INTREGS + S_LR]
> mov sp, x1
>
> --
> 2.30.2
>