From: Andy Lutomirski <luto@amacapital.net>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>,
Borislav Petkov <bp@alien8.de>,
linux-kernel@vger.kernel.org, x86@kernel.org,
kvm@vger.kernel.org, linux-crypto@vger.kernel.org,
ak@linux.intel.com, herbert@gondor.apana.org.au,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
"H. Peter Anvin" <hpa@zytor.com>, Tony Luck <tony.luck@intel.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
David Rientjes <rientjes@google.com>,
Sean Christopherson <seanjc@google.com>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [RFC Part2 PATCH 04/30] x86/mm: split the physmap when adding the page in RMP table
Date: Mon, 19 Apr 2021 11:37:19 -0700 [thread overview]
Message-ID: <D67BDFB6-84AA-4CA3-A951-7EEE0E4B4B26@amacapital.net> (raw)
In-Reply-To: <535400b4-0593-a7ca-1548-532ee1fefbd7@intel.com>
> On Apr 19, 2021, at 11:33 AM, Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 4/19/21 11:10 AM, Andy Lutomirski wrote:
>> I’m confused by this scenario. This should only affect physical pages
>> that are in the 2M area that contains guest memory. But, if we have a
>> 2M direct map PMD entry that contains kernel data and guest private
>> memory, we’re already in a situation in which the kernel touching
>> that memory would machine check, right?
>
> Not machine check, but page fault. Do machine checks even play a
> special role in SEV-SNP? I thought that was only TDX?
Brain fart.
>
> My point was just that you can't _easily_ do the 2M->4k kernel mapping
> demotion in a page fault handler, like I think Borislav was suggesting.
We are certainly toast if this hits the stack. Or if it hits a page table or the GDT or IDT :). The latter delightful choices would be triple faults.
I sure hope the code we use to split a mapping is properly NMI safe.
>
>> ISTM we should fully unmap any guest private page from the kernel and
>> all host user pagetables before actually making it be a guest private
>> page.
>
> Yes, that sounds attractive. Then, we'd actually know if the host
> kernel was doing stray reads somehow because we'd get a fault there too.
next prev parent reply other threads:[~2021-04-19 18:37 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 17:04 [RFC Part2 PATCH 00/30] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 01/30] x86: Add the host SEV-SNP initialization support Brijesh Singh
2021-03-25 14:58 ` Dave Hansen
2021-03-25 15:31 ` Brijesh Singh
2021-03-25 15:51 ` Dave Hansen
2021-03-25 17:41 ` Brijesh Singh
2021-04-14 7:27 ` Borislav Petkov
2021-04-14 22:48 ` Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 02/30] x86/sev-snp: add RMP entry lookup helpers Brijesh Singh
2021-04-15 16:57 ` Borislav Petkov
2021-04-15 18:08 ` Brijesh Singh
2021-04-15 19:50 ` Borislav Petkov
2021-04-15 22:18 ` Brijesh Singh
2021-04-15 17:03 ` Borislav Petkov
2021-04-15 18:09 ` Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 03/30] x86: add helper functions for RMPUPDATE and PSMASH instruction Brijesh Singh
2021-04-15 18:00 ` Borislav Petkov
2021-04-15 18:15 ` Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 04/30] x86/mm: split the physmap when adding the page in RMP table Brijesh Singh
2021-03-25 15:17 ` Dave Hansen
2021-04-19 12:32 ` Borislav Petkov
2021-04-19 15:25 ` Brijesh Singh
2021-04-19 16:52 ` Borislav Petkov
[not found] ` <30bff969-e8cf-a991-7660-054ea136855a@amd.com>
2021-04-19 17:58 ` Dave Hansen
2021-04-19 18:10 ` Andy Lutomirski
2021-04-19 18:33 ` Dave Hansen
2021-04-19 18:37 ` Andy Lutomirski [this message]
2021-04-20 9:51 ` Borislav Petkov
2021-04-19 21:25 ` Brijesh Singh
2021-04-20 9:47 ` Borislav Petkov
2021-03-24 17:04 ` [RFC Part2 PATCH 05/30] x86: define RMP violation #PF error code Brijesh Singh
2021-03-24 18:03 ` Dave Hansen
2021-03-25 14:32 ` Brijesh Singh
2021-03-25 14:34 ` Dave Hansen
2021-04-20 10:32 ` Borislav Petkov
2021-04-20 21:37 ` Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 06/30] x86/fault: dump the RMP entry on #PF Brijesh Singh
2021-03-24 17:47 ` Andy Lutomirski
2021-03-24 20:35 ` Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 07/30] mm: add support to split the large THP based on RMP violation Brijesh Singh
2021-03-25 14:30 ` Dave Hansen
2021-03-25 14:48 ` Dave Hansen
2021-03-25 15:24 ` Brijesh Singh
2021-03-25 15:59 ` Dave Hansen
2021-04-21 12:59 ` Vlastimil Babka
2021-04-21 13:43 ` Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 08/30] crypto:ccp: define the SEV-SNP commands Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 09/30] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 10/30] crypto: ccp: shutdown SNP firmware on kexec Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 11/30] crypto:ccp: provide APIs to issue SEV-SNP commands Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 12/30] crypto ccp: handle the legacy SEV command when SNP is enabled Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 13/30] KVM: SVM: add initial SEV-SNP support Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 14/30] KVM: SVM: make AVIC backing, VMSA and VMCB memory allocation SNP safe Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 15/30] KVM: SVM: define new SEV_FEATURES field in the VMCB Save State Area Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 16/30] KVM: SVM: add KVM_SNP_INIT command Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 17/30] KVM: SVM: add KVM_SEV_SNP_LAUNCH_START command Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 18/30] KVM: SVM: add KVM_SEV_SNP_LAUNCH_UPDATE command Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 19/30] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 20/30] KVM: SVM: add KVM_SEV_SNP_LAUNCH_FINISH command Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 21/30] KVM: X86: Add kvm_x86_ops to get the max page level for the TDP Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 22/30] x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by SEV Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 23/30] KVM: X86: Introduce kvm_mmu_get_tdp_walk() for SEV-SNP use Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 24/30] KVM: X86: define new RMP check related #NPF error bits Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 25/30] KVM: X86: update page-fault trace to log the 64-bit error code Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 26/30] KVM: SVM: add support to handle GHCB GPA register VMGEXIT Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 27/30] KVM: SVM: add support to handle MSR based Page State Change VMGEXIT Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 28/30] KVM: SVM: add support to handle " Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 29/30] KVM: X86: export the kvm_zap_gfn_range() for the SNP use Brijesh Singh
2021-03-24 17:04 ` [RFC Part2 PATCH 30/30] KVM: X86: Add support to handle the RMP nested page fault Brijesh Singh
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