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Re: [PATCH v5 1/2] xen/arm: fix arm_iommu_map_page after f9f6b22abf1d
- To: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>, Julien Grall <julien@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Wed, 6 Aug 2025 10:30:45 -0400
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- Cc: Stefano Stabellini <stefano.stabellini@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, "Michal Orzel" <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 06 Aug 2025 14:31:03 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2025-08-06 09:58, Stewart Hildebrand wrote:
On 7/26/25 05:23, Julien Grall wrote:
Hi,
On 25/07/2025 15:01, Stewart Hildebrand wrote:
From: Stefano Stabellini <stefano.stabellini@xxxxxxx>
Up until f9f6b22abf1d "xen/arm: Map ITS doorbell register to IOMMU page
tables" the only caller of iommu_map on ARM was grant_table.c which has
a specific usage model and restrictions as described by the in-code
comment in arm_iommu_map_page.
f9f6b22abf1d introduced a second caller to iommu_map on ARM:
vgic_v3_its_init_virtual. This specific statement in the
f9f6b22abf1d commit message is partially wrong:
"Note that the 1:1 check in arm_iommu_map_page remains for now, as
virtual ITSes are currently only created for hwdom where the doorbell
mapping is always 1:1."
Leading to crashes any time the hardware domain is not direct-mapped
(e.g. cache coloring and non-Dom0 hardware domain):
(XEN) Xen BUG at drivers/passthrough/arm/iommu_helpers.c:47
[...]
(XEN) Xen call trace:
(XEN) [<00000a000024c758>] arm_iommu_map_page+0x80/0x90 (PC)
(XEN) [<00000a000024c750>] arm_iommu_map_page+0x78/0x90 (LR)
(XEN) [<00000a0000250884>] iommu_map+0xcc/0x29c
(XEN) [<00000a0000288024>] vgic_v3_its_init_domain+0x18c/0x1e8
(XEN) [<00000a0000285228>] vgic-v3.c#vgic_v3_domain_init+0x168/0x21c
(XEN) [<00000a0000281dcc>] domain_vgic_init+0x14c/0x210
(XEN) [<00000a00002705a4>] arch_domain_create+0x150/0x1f0
(XEN) [<00000a00002055e8>] domain_create+0x47c/0x6c0
(XEN) [<00000a00002cf090>] create_domUs+0x7f8/0x8cc
(XEN) [<00000a00002eb588>] start_xen+0x8f4/0x998
(XEN) [<00000a000020018c>] head.o#primary_switched+0x4/0x10
Specifically, non-1:1 hardware domain exists with cache coloring
enabled. For that, is_domain_direct_mapped(d) is false but
domain_use_host_layout(d) is true.
Change the is_domain_direct_mapped(d) checks in arm_iommu_map_page and
arm_iommu_unmap_page into domain_use_host_layout(d) checks.
Drop stale in-code comment specific to grant table mappings.
Fixes: f9f6b22abf1d ("xen/arm: Map ITS doorbell register to IOMMU page tables")
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
Thanks for the review! Is this ready to be committed?
Tested-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Thanks,
Jason
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