Messages in this thread |  | | From | Jerry Snitselaar <> | Subject | Re: Question about domain_init (v5.3-v5.7) | Date | Fri, 27 Nov 2020 00:48:25 -0700 |
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Lu Baolu @ 2020-11-26 19:12 MST:
> Hi Jerry, > > On 11/27/20 5:35 AM, Jerry Snitselaar wrote: >> Lu Baolu @ 2020-11-26 04:01 MST: >> >>> Hi Jerry, >>> >>> On 2020/11/26 4:27, Jerry Snitselaar wrote: >>>> Is there a reason we check the requested guest address width against >>>> the >>>> iommu's mgaw, instead of the agaw that we already know for the iommu? >>>> I've run into a case with a new system where the mgaw reported is 57, >>>> but if they set PAE to 46 instead of 52 in the bios, then sagaw reports >>>> the highest supported agaw is 48 and the domain_init code fails here. In >>> >>> Isn't this a platform bug? If it's too late to fix it in the BIOS, you >>> maybe have to add a platform specific quirk to set mgaw to the highest >>> supported agaw? >>> >>> Best regards, >>> baolu >> Is there somewhere you can point me to that discusses how they >> should be >> setting the mgaw? I misunderstood when I previously asked you about >> whether the mgaw could be a value that was greater than any of sagaw. >> If it is a bios issue, then they should fix it there. > > MGAW indicates the max gpa width supported by 2nd translation. The VT-d > spec requires that this value must be at least equal to the host > physical addressibility. According to this, BIOS is good, right? >
Yes, the host address width is 46. MGAW reports 57 (56+1), and highest sagaw bit is for 48.
> For this failure case, domain_init() just wants to find a suitable agaw > for the private domain. I think it makes sense to check against > iommu->agaw instead of cap_mgaw. > > Best regards, > baolu > >> >>> >>>> other places like prepare_domain_attach_device, the dmar domain agaw >>>> gets adjusted down to the iommu agaw. The agaw of the iommu gets >>>> determined based off what is reported for sagaw. I'm wondering if it >>>> can't instead do: >>>> --- >>>> drivers/iommu/intel-iommu.c | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> diff --git a/drivers/iommu/intel-iommu.c >>>> b/drivers/iommu/intel-iommu.c >>>> index 6ca5c92ef2e5..a8e41ec36d9e 100644 >>>> --- a/drivers/iommu/intel-iommu.c >>>> +++ b/drivers/iommu/intel-iommu.c >>>> @@ -1862,8 +1862,8 @@ static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu, >>>> domain_reserve_special_ranges(domain); >>>> /* calculate AGAW */ >>>> - if (guest_width > cap_mgaw(iommu->cap)) >>>> - guest_width = cap_mgaw(iommu->cap); >>>> + if (guest_width > agaw_to_width(iommu->agaw)) >>>> + guest_width = agaw_to_width(iommu->agaw); >>>> domain->gaw = guest_width; >>>> adjust_width = guestwidth_to_adjustwidth(guest_width); >>>> agaw = width_to_agaw(adjust_width); >>>> -- >>>> 2.27.0 >>>> >>>> Thoughts? With the former code the ehci device for the ilo fails when >>>> trying to get a private domain. >>>> Thanks, >>>> Jerry >>>> >>
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