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Message-ID: <24a4eb65-5e1b-44f9-a8ae-71f5f8f26ceb@amd.com>
Date: Wed, 15 May 2024 02:02:12 +0700
From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To: Michael Kelley <mhklinux@...look.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
"joro@...tes.org" <joro@...tes.org>
Cc: "thomas.lendacky@....com" <thomas.lendacky@....com>,
"vasant.hegde@....com" <vasant.hegde@....com>,
"michael.roth@....com" <michael.roth@....com>,
"jon.grimm@....com" <jon.grimm@....com>,
"rientjes@...gle.com" <rientjes@...gle.com>
Subject: Re: [PATCH 0/9] iommu/amd: Add AMD IOMMU emulation support for
SEV-SNP guest kernel
On 5/14/2024 3:05 AM, Michael Kelley wrote:
> From: Suravee Suthikulpanit<suravee.suthikulpanit@....com> Sent: Tuesday, April 30, 2024 8:24 AM
>> To boot a VM w/ x2APIC ID > 255, guest interrupt remapping emulation
>> is required.
>
> Top-level question: Is there a reason the MSI extended destination ID mechanism is
> insufficient to avoid the need for interrupt remapping? (see function pointer
> "msi_ext_dest_id"). I'm unclear on whether it is or not. If it is not sufficient, perhaps
> you could explain why.
In case of running a Linux VM w/ QEMU/KVM as hypervisor, the
qemu-system-x86_64 option kvm-msi-ext-dest-id=on would allow booting the
VM w/ x2APIC ID > 255. However, for other hypervisor, it might not
support this feature.
>> For SEV guest, this can be achieved using an emulated
>> AMD IOMMU.
> You've used "SEV" here and in several other places. I think you intend this to be
> the more specific "SEV-SNP", and exclude SEV and SEV-ES. For avoid any confusion,
> I'd suggest using "SEV-SNP" throughout if that's what you mean.
Actually, The CC_ATTR_GUEST_MEM_ENCRYPT attribute is true for all SEV
guests, so this will enable IOMMU emulation for all SEV guests.
Thanks,
Suravee
> Michael
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