Re: [PATCH v3 04/15] KVM: arm64: Teach ptdump about FEAT_XNX permissions

[Nathan Chancellor <nathan@kernel.org>]

Hi Oliver,

On Mon, Nov 24, 2025 at 11:01:46AM -0800, Oliver Upton wrote:
> Although KVM doesn't make direct use of the feature, guest hypervisors
> can use FEAT_XNX which influences the permissions of the shadow stage-2.
> Update ptdump to separately print the privileged and unprivileged
> execute permissions.
> 
> Signed-off-by: Oliver Upton <oupton@kernel.org>
> ---
>  arch/arm64/kvm/ptdump.c | 35 +++++++++++++++++++++++++++--------
>  1 file changed, 27 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
> index dc5acfb00af9..bd722383d0e3 100644
> --- a/arch/arm64/kvm/ptdump.c
> +++ b/arch/arm64/kvm/ptdump.c
> @@ -31,27 +31,46 @@ static const struct ptdump_prot_bits stage2_pte_bits[] = {
>  		.val	= PTE_VALID,
>  		.set	= " ",
>  		.clear	= "F",
> -	}, {
> +	},
> +	{
>  		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R,
>  		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R,
>  		.set	= "R",
>  		.clear	= " ",
> -	}, {
> +	},
> +	{
>  		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
>  		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W,
>  		.set	= "W",
>  		.clear	= " ",
> -	}, {
> +	},
> +	{
>  		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> -		.val	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> -		.set	= "NX",
> -		.clear	= "x ",
> -	}, {
> +		.val	= FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b00),
> +		.set	= "px ux ",
> +	},
> +	{
> +		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> +		.val	= FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b01),
> +		.set	= "PXNux ",
> +	},
> +	{
> +		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> +		.val	= FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b10),
> +		.set	= "PXNUXN",
> +	},
> +	{
> +		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN,
> +		.val	= FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b11),
> +		.set	= "px UXN",
> +	},
> +	{
>  		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_AF,
>  		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF,
>  		.set	= "AF",
>  		.clear	= "  ",
> -	}, {
> +	},
> +	{
>  		.mask	= PMD_TYPE_MASK,
>  		.val	= PMD_TYPE_SECT,
>  		.set	= "BLK",
> -- 
> 2.47.3
> 

This change as commit 81e9fe5c6f25 ("KVM: arm64: Teach ptdump about
FEAT_XNX permissions") in -next does not build for me.

GCC 15.2.0

  In file included from arch/arm64/include/asm/sysreg.h:1155,
                   from arch/arm64/include/asm/memory.h:219,
                   from arch/arm64/include/asm/thread_info.h:17,
                   from include/linux/thread_info.h:60,
                   from arch/arm64/include/asm/preempt.h:5,
                   from include/linux/preempt.h:79,
                   from include/linux/spinlock.h:56,
                   from include/linux/wait.h:9,
                   from include/linux/wait_bit.h:8,
                   from include/linux/fs.h:7,
                   from include/linux/debugfs.h:15,
                   from arch/arm64/kvm/ptdump.c:9:
  include/linux/bitfield.h:114:9: error: braced-group within expression allowed only inside a function
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:49:27: note: in expansion of macro 'FIELD_PREP'
     49 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b00),
        |                           ^~~~~~~~~~
  include/linux/bitfield.h:114:9: error: braced-group within expression allowed only inside a function
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:54:27: note: in expansion of macro 'FIELD_PREP'
     54 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b01),
        |                           ^~~~~~~~~~
  include/linux/bitfield.h:114:9: error: braced-group within expression allowed only inside a function
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:59:27: note: in expansion of macro 'FIELD_PREP'
     59 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b10),
        |                           ^~~~~~~~~~
  include/linux/bitfield.h:114:9: error: braced-group within expression allowed only inside a function
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:64:27: note: in expansion of macro 'FIELD_PREP'
     64 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b11),
        |                           ^~~~~~~~~~

clang 21.1.6:

  arch/arm64/kvm/ptdump.c:49:10: error: statement expression not allowed at file scope
     49 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b00),
        |                           ^
  include/linux/bitfield.h:114:2: note: expanded from macro 'FIELD_PREP'
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:54:10: error: statement expression not allowed at file scope
     54 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b01),
        |                           ^
  include/linux/bitfield.h:114:2: note: expanded from macro 'FIELD_PREP'
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:59:10: error: statement expression not allowed at file scope
     59 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b10),
        |                           ^
  include/linux/bitfield.h:114:2: note: expanded from macro 'FIELD_PREP'
    114 |         ({                                                              \
        |         ^
  arch/arm64/kvm/ptdump.c:64:10: error: statement expression not allowed at file scope
     64 |                 .val    = FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, 0b11),
        |                           ^
  include/linux/bitfield.h:114:2: note: expanded from macro 'FIELD_PREP'
    114 |         ({                                                              \
        |         ^

Cheers,
Nathan