The comment above the NULL collection check in vgic_its_save_ite()
names only MAPC with V=0, which is UNPREDICTABLE. The route that
requires the check is clearing GITS_BASER<coll>.Valid on a disabled
ITS, a legitimate operation that orphans every ITE at once. Name both
routes.

No functional change intended.

Suggested-by: Eric Auger <eauger@redhat.com>
Link: https://lore.kernel.org/all/0ce5e496-a067-48fd-80d2-94fe9981d505@redhat.com/
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---

Notes:
    Based on kvmarm/next, since the comment this reworks was added by
    c6c156d931c3 ("KVM: arm64: vgic-its: Don't dereference a NULL collection
    on ITT save") and is not in a release yet.

 arch/arm64/kvm/vgic/vgic-its.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index f6538b1976f9b..26c665e0a2386 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -2112,9 +2112,9 @@ static int vgic_its_save_ite(struct vgic_its *its, struct its_device *dev,
 	u64 val;
 
 	/*
-	 * MAPC with V=0 keeps the ITEs mapped but drops their collection,
-	 * and with it the ICID. Save a zeroed entry, which the restore path
-	 * reads back as invalid.
+	 * MAPC with V=0 and clearing GITS_BASER<coll>.Valid both keep the
+	 * ITEs mapped while dropping their collection, and with it the ICID.
+	 * Save a zeroed entry, which the restore path reads back as invalid.
 	 */
 	if (!ite->collection)
 		return vgic_its_write_entry_lock(its, gpa, 0ULL, ite);

base-commit: 57e7cf13ac26bf1a3dba6cfa601f7b2481811575
-- 
2.39.5

On Mon, 17 Aug 2026 10:27:05 +0100, Fuad Tabba wrote:
> The comment above the NULL collection check in vgic_its_save_ite()
> names only MAPC with V=0, which is UNPREDICTABLE. The route that
> requires the check is clearing GITS_BASER<coll>.Valid on a disabled
> ITS, a legitimate operation that orphans every ITE at once. Name both
> routes.
> 
> No functional change intended.
> 
> [...]

Applied to next, thanks!

[1/1] KVM: arm64: vgic-its: Reword the comment on a collection-less ITE
      commit: 356abf7cedff742621c9b7ae8ecfa7d0febb0b9e

Cheers,

	M.
-- 
Without deviation from the norm, progress is not possible.

On 8/17/26 11:27 AM, Fuad Tabba wrote:
> The comment above the NULL collection check in vgic_its_save_ite()
> names only MAPC with V=0, which is UNPREDICTABLE. The route that
> requires the check is clearing GITS_BASER<coll>.Valid on a disabled
> ITS, a legitimate operation that orphans every ITE at once. Name both
> routes.
> 
> No functional change intended.
> 
> Suggested-by: Eric Auger <eauger@redhat.com>
> Link: https://lore.kernel.org/all/0ce5e496-a067-48fd-80d2-94fe9981d505@redhat.com/
> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric


> ---
> 
> Notes:
>     Based on kvmarm/next, since the comment this reworks was added by
>     c6c156d931c3 ("KVM: arm64: vgic-its: Don't dereference a NULL collection
>     on ITT save") and is not in a release yet.
> 
>  arch/arm64/kvm/vgic/vgic-its.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
> index f6538b1976f9b..26c665e0a2386 100644
> --- a/arch/arm64/kvm/vgic/vgic-its.c
> +++ b/arch/arm64/kvm/vgic/vgic-its.c
> @@ -2112,9 +2112,9 @@ static int vgic_its_save_ite(struct vgic_its *its, struct its_device *dev,
>  	u64 val;
>  
>  	/*
> -	 * MAPC with V=0 keeps the ITEs mapped but drops their collection,
> -	 * and with it the ICID. Save a zeroed entry, which the restore path
> -	 * reads back as invalid.
> +	 * MAPC with V=0 and clearing GITS_BASER<coll>.Valid both keep the
> +	 * ITEs mapped while dropping their collection, and with it the ICID.
> +	 * Save a zeroed entry, which the restore path reads back as invalid.
>  	 */
>  	if (!ite->collection)
>  		return vgic_its_write_entry_lock(its, gpa, 0ULL, ite);
> 
> base-commit: 57e7cf13ac26bf1a3dba6cfa601f7b2481811575