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Re: [PATCH v8] xen/arm: pci: introduce PCI_PASSTHROUGH Kconfig option
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
- Date: Wed, 23 Jul 2025 10:26:29 -0400
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- Cc: Rahul Singh <rahul.singh@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, "Volodymyr Babchuk" <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 23 Jul 2025 14:27:05 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 7/23/25 06:18, Jan Beulich wrote:
> On 13.06.2025 17:17, Stewart Hildebrand wrote:
>> --- a/xen/arch/arm/Kconfig
>> +++ b/xen/arch/arm/Kconfig
>> @@ -8,6 +8,8 @@ config ARM_64
>> depends on !ARM_32
>> select 64BIT
>> select HAS_FAST_MULTIPLY
>> + select HAS_VPCI_GUEST_SUPPORT if PCI_PASSTHROUGH
>> + select HAS_PASSTHROUGH if PCI_PASSTHROUGH
>
> As I just learned, this change (or maybe it was the "select HAS_PCI"
> further down) has exposed the quarantining Kconfig option prompt, which
> (aiui) is entirely meaningless on Arm. IOW I think further adjustments
> are necessary.
>
> Jan
Not entirely meaningless - the choice between "none" and "basic" still
seems relevant. Just "scratch page" quarantining hasn't been implemented
in any of the Arm iommu drivers.
Perhaps just the IOMMU_QUARANTINE_SCRATCH_PAGE option should be hidden
on Arm (or only exposed on x86)? E.g.:
diff --git a/xen/drivers/passthrough/Kconfig b/xen/drivers/passthrough/Kconfig
index 561f9694b2a6..51c54ed530b0 100644
--- a/xen/drivers/passthrough/Kconfig
+++ b/xen/drivers/passthrough/Kconfig
@@ -90,4 +90,5 @@ choice
bool "basic"
config IOMMU_QUARANTINE_SCRATCH_PAGE
bool "scratch page"
+ depends on X86
endchoice
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