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Re: [PATCH for-4.18 v3] x86/pvh: fix identity mapping of low 1MB
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Wed, 18 Oct 2023 05:09:53 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Paul Durrant <paul@xxxxxxx>
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- Thread-topic: [PATCH for-4.18 v3] x86/pvh: fix identity mapping of low 1MB
Hi Roger,
> On Oct 17, 2023, at 16:29, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>
> The mapping of memory regions below the 1MB mark was all done by the PVH dom0
> builder code, causing the region to be avoided by the arch specific IOMMU
> hardware domain initialization code. That lead to the IOMMU being enabled
> without reserved regions in the low 1MB identity mapped in the p2m for PVH
> hardware domains. Firmware which happens to be missing RMRR/IVMD ranges
> describing E820 reserved regions in the low 1MB would transiently trigger
> IOMMU
> faults until the p2m is populated by the PVH dom0 builder:
>
> AMD-Vi: IO_PAGE_FAULT: 0000:00:13.1 d0 addr 00000000000eb380 flags 0x20 RW
> AMD-Vi: IO_PAGE_FAULT: 0000:00:13.1 d0 addr 00000000000eb340 flags 0
> AMD-Vi: IO_PAGE_FAULT: 0000:00:13.2 d0 addr 00000000000ea1c0 flags 0
> AMD-Vi: IO_PAGE_FAULT: 0000:00:14.5 d0 addr 00000000000eb480 flags 0x20 RW
> AMD-Vi: IO_PAGE_FAULT: 0000:00:12.0 d0 addr 00000000000eb080 flags 0x20 RW
> AMD-Vi: IO_PAGE_FAULT: 0000:00:14.5 d0 addr 00000000000eb400 flags 0
> AMD-Vi: IO_PAGE_FAULT: 0000:00:12.0 d0 addr 00000000000eb040 flags 0
>
> Those errors have been observed on the osstest pinot{0,1} boxes (AMD Fam15h
> Opteron(tm) Processor 3350 HE).
>
> Rely on the IOMMU arch init code to create any identity mappings for reserved
> regions in the low 1MB range (like it already does for reserved regions
> elsewhere), and leave the mapping of any holes to be performed by the dom0
> builder code.
>
> Fixes: 6b4f6a31ace1 ('x86/PVH: de-duplicate mappings for first Mb of Dom0
> memory')
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
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