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Message-ID: <298d2e19-566d-2e58-b639-724c10885646@amd.com>
Date: Mon, 12 Jul 2021 11:49:52 -0500
From: Brijesh Singh <brijesh.singh@....com>
To: Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
linux-coco@...ts.linux.dev, linux-mm@...ck.org,
linux-crypto@...r.kernel.org
Cc: brijesh.singh@....com, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
Tom Lendacky <thomas.lendacky@....com>,
"H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Dov Murik <dovmurik@...ux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@....com>,
Borislav Petkov <bp@...en8.de>,
Michael Roth <michael.roth@....com>,
Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part2 RFC v4 10/40] x86/fault: Add support to handle the
RMP fault for user address
On 7/12/21 11:29 AM, Dave Hansen wrote:
> On 7/12/21 9:24 AM, Brijesh Singh wrote:
>> Apologies if I was not clear in the messaging, that's exactly what I
>> mean that we don't feed RMP entries during the page state change.
>>
>> The sequence of the operation is:
>>
>> 1. Guest issues a VMGEXIT (page state change) to add a page in the RMP
>> 2. Hyperivosr adds the page in the RMP table.
>>
>> The check will be inside the hypervisor (#2), to query the backing page
>> type, if the backing page is from the hugetlbfs, then don't add the page
>> in the RMP, and fail the page state change VMGEXIT.
>
> Right, but *LOOOOOONG* before that, something walked the page tables and
> stuffed the PFN into the NPT (that's the AMD equivalent of EPT, right?).
> You could also avoid this whole mess by refusing to allow hugetblfs to
> be mapped into the guest in the first place.
>
Ah, that should be doable. For SEV stuff, we require the VMM to register
the memory region to the hypervisor during the VM creation time. I can
check the hugetlbfs while registering the memory region and fail much
earlier.
thanks
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