Re: [PATCH] x86/domctl: restore all registers in arch_{get,set}_info_guest()

[Frediano Ziglio <freddy77@xxxxxxxxx>]

On Mon, 20 Jul 2026 at 01:13, Marek Marczykowski-Górecki
<marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Commit 9f892f84c279 ("x86/domctl: Stop using XLAT_cpu_user_regs()")
> converted memcpy() of the cpu_user_regs structure to explicit copy of
> its fields. In the compat case, it intentionally missed few of them,
> named in the commit message. But the 64bit case missed also r8-r15
> registers, which was not intentional. This, at least, caused Linux
> 6.18.x crash when resuming PVH domU.
>
> Fix it by adding missing assignments.
>
> Fixes: 9f892f84c279 ("x86/domctl: Stop using XLAT_cpu_user_regs()")
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> ---
>  xen/arch/x86/domain.c | 8 ++++++++
>  xen/arch/x86/domctl.c | 8 ++++++++
>  2 files changed, 16 insertions(+)
>
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index 1d458f1372e5..ba7244ccc513 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -1255,6 +1255,14 @@ int arch_set_info_guest(
>
>      if ( !compat )
>      {
> +        v->arch.user_regs.r15               = c.nat->user_regs.r15;
> +        v->arch.user_regs.r14               = c.nat->user_regs.r14;
> +        v->arch.user_regs.r13               = c.nat->user_regs.r13;
> +        v->arch.user_regs.r12               = c.nat->user_regs.r12;
> +        v->arch.user_regs.r11               = c.nat->user_regs.r11;
> +        v->arch.user_regs.r10               = c.nat->user_regs.r10;
> +        v->arch.user_regs.r9                = c.nat->user_regs.r9;
> +        v->arch.user_regs.r8                = c.nat->user_regs.r8;
>          v->arch.user_regs.rbx               = c.nat->user_regs.rbx;
>          v->arch.user_regs.rcx               = c.nat->user_regs.rcx;
>          v->arch.user_regs.rdx               = c.nat->user_regs.rdx;
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index 07f712a0a40d..3ea4c650eee0 100644
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -1481,6 +1481,14 @@ void arch_get_info_guest(struct vcpu *v, 
> vcpu_guest_context_u c)
>      if ( !compat )
>      {
>          /* Backing memory is pre-zeroed. */
> +        c.nat->user_regs.r15               = v->arch.user_regs.r15;
> +        c.nat->user_regs.r14               = v->arch.user_regs.r14;
> +        c.nat->user_regs.r13               = v->arch.user_regs.r13;
> +        c.nat->user_regs.r12               = v->arch.user_regs.r12;
> +        c.nat->user_regs.r11               = v->arch.user_regs.r11;
> +        c.nat->user_regs.r10               = v->arch.user_regs.r10;
> +        c.nat->user_regs.r9                = v->arch.user_regs.r9;
> +        c.nat->user_regs.r8                = v->arch.user_regs.r8;
>          c.nat->user_regs.rbx               = v->arch.user_regs.rbx;
>          c.nat->user_regs.rcx               = v->arch.user_regs.rcx;
>          c.nat->user_regs.rdx               = v->arch.user_regs.rdx;

Reviewed-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>

Frediano