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    SubjectRe: [PATCH V6 6/8] x86/entry: Convert SWAPGS to swapgs and remove the definition of SWAPGS
    On Mon, May 02, 2022 at 02:18:35PM +0200, Juergen Gross wrote:
    > The syscall will land in the hypervisor, which then will activate
    > the related registered callback (xen_sysenter_target).

    Aha, that would do a bit of a fixup and then go to the common label
    entry_SYSENTER_compat_after_hwframe.

    We probably should document this so that it is clear what uses those...

    ---
    diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
    index 9da5eef9affe..93065c4914ad 100644
    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -103,6 +103,11 @@ SYM_INNER_LABEL(entry_SYSCALL_64_safe_stack, SYM_L_GLOBAL)
    pushq %r11 /* pt_regs->flags */
    pushq $__USER_CS /* pt_regs->cs */
    pushq %rcx /* pt_regs->ip */
    +
    + /*
    + * XENPV jumps here after frame fixup in the respective entry points in
    + * ...xen-asm.S.
    + */
    SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
    pushq %rax /* pt_regs->orig_ax */

    diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
    index c5aeb0819707..b473f8e17afc 100644
    --- a/arch/x86/entry/entry_64_compat.S
    +++ b/arch/x86/entry/entry_64_compat.S
    @@ -71,6 +71,11 @@ SYM_CODE_START(entry_SYSENTER_compat)
    pushfq /* pt_regs->flags (except IF = 0) */
    pushq $__USER32_CS /* pt_regs->cs */
    pushq $0 /* pt_regs->ip = 0 (placeholder) */
    +
    + /*
    + * XENPV jumps here after frame fixup in the respective entry points in
    + * ...xen-asm.S.
    + */
    SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)

    /*
    > I wouldn't insist on the CONFIG_DEBUG_ENTRY chunk.

    Ok, simpler asm, cool, let's do it then.

    Thx.

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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