From: Brijesh Singh <brijesh.singh@amd.com>
To: Vlastimil Babka <vbabka@suse.cz>,
Sean Christopherson <seanjc@google.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, linux-efi@vger.kernel.org,
platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev,
linux-mm@kvack.org, linux-crypto@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Dov Murik <dovmurik@linux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Borislav Petkov <bp@alien8.de>,
Michael Roth <michael.roth@amd.com>,
tony.luck@intel.com, npmccallum@redhat.com,
brijesh.ksingh@gmail.com
Subject: Re: [PATCH Part2 RFC v4 07/40] x86/sev: Split the physmap when adding the page in RMP table
Date: Fri, 30 Jul 2021 11:10:01 -0500 [thread overview]
Message-ID: <6c2eefa9-a7f2-399b-f38f-bfae580cdca9@amd.com> (raw)
In-Reply-To: <b6793038-c24b-a65b-1ca4-ed581b254ff4@suse.cz>
On 7/30/21 6:31 AM, Vlastimil Babka wrote:
> On 7/15/21 9:38 PM, Brijesh Singh wrote:
>>
>> On 7/15/21 1:39 PM, Sean Christopherson wrote:
>>> On Thu, Jul 15, 2021, Brijesh Singh wrote:
>>>> The memfd_secrets uses the set_direct_map_{invalid,default}_noflush() and it
>>>> is designed to remove/add the present bit in the direct map. We can't use
>>>> them, because in our case the page may get accessed by the KVM (e.g
>>>> kvm_guest_write, kvm_guest_map etc).
>>> But KVM should never access a guest private page, i.e. the direct map should
>>> always be restored to PRESENT before KVM attempts to access the page.
>>>
>> Yes, KVM should *never* access the guest private pages. So, we could potentially
>> enhance the RMPUPDATE() to check for the assigned and act accordingly.
> I think I'm not the first one suggesting it, but IMHO the best solution would be
> to leave direct map alone (except maybe in some debugging/development mode where
> you could do the unmapping to catch unexpected host accesses), and once there's
> a situation with host accessing a shared page of the guest, it would temporarily
> kmap() it outside of the direct map. Shouldn't these situations be rare enough,
> and already recognizable due to the need to set up the page sharing in the first
> place, that this approach would be feasible?
The host accessing a guest shared is not rare, some shared pages are
accessed on every VM-Entry and Exit. However, there are limited number
of such pages and we could track and temporary kmap() outside of the
direct map. The main challenge is when a host pages are added as
'private' in the RMP table.
e.g
page = alloc_page(GFP_KERNEL_ACCOUNT);
// firmware context page
rmp_make_firmware(page_to_pfn(page), PG_LEVEL_4K);
or
// VMSA page
rmp_make_private(page_to_pfn(page), 0, sev->asid, PG_LEVEL_4K);
The page is added as 4K in the RMP entry; If the pfn is part of the
large direct map then hardware will raise an RMP violation and to
resolve the fault we must split the direct map.
thanks
>
>> Are you thinking something along the line of this:
>>
>> int rmpupdate(struct page *page, struct rmpupdate *val)
>> {
>> ...
>>
>> /*
>> * If page is getting assigned in the RMP entry then unmap
>> * it from the direct map before its added in the RMP table.
>> */
>> if (val.assigned)
>> set_direct_map_invalid_noflush(page_to_virt(page), 1);
>>
>> ...
>>
>> /*
>> * If the page is getting unassigned then restore the mapping
>> * in the direct map after its removed from the RMP table.
>> */
>> if (!val.assigned)
>> set_direct_map_default_noflush(page_to_virt(page), 1);
>>
>> ...
>> }
>>
>> thanks
next prev parent reply other threads:[~2021-07-30 16:10 UTC|newest]
Thread overview: 178+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 18:35 [PATCH Part2 RFC v4 00/40] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 01/40] KVM: SVM: Add support to handle AP reset MSR protocol Brijesh Singh
2021-07-14 20:17 ` Sean Christopherson
2021-07-15 7:39 ` Joerg Roedel
2021-07-15 13:42 ` Tom Lendacky
2021-07-15 15:45 ` Sean Christopherson
2021-07-15 17:05 ` Tom Lendacky
2021-07-07 18:35 ` [PATCH Part2 RFC v4 02/40] KVM: SVM: Provide the Hypervisor Feature support VMGEXIT Brijesh Singh
2021-07-14 20:37 ` Sean Christopherson
2021-07-14 21:00 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 03/40] x86/cpufeatures: Add SEV-SNP CPU feature Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 04/40] x86/sev: Add the host SEV-SNP initialization support Brijesh Singh
2021-07-14 21:07 ` Sean Christopherson
2021-07-14 22:02 ` Brijesh Singh
2021-07-14 22:06 ` Sean Christopherson
2021-07-14 22:11 ` Brijesh Singh
2022-06-02 11:47 ` Jarkko Sakkinen
2022-06-06 11:42 ` Dr. David Alan Gilbert
2021-07-07 18:35 ` [PATCH Part2 RFC v4 05/40] x86/sev: Add RMP entry lookup helpers Brijesh Singh
2021-07-15 18:37 ` Sean Christopherson
2021-07-15 19:28 ` Brijesh Singh
2021-07-16 17:22 ` Brijesh Singh
2021-07-20 22:06 ` Sean Christopherson
2021-07-20 23:10 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 06/40] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction Brijesh Singh
2021-07-12 18:44 ` Peter Gonda
2021-07-12 19:00 ` Dave Hansen
2021-07-15 18:56 ` Sean Christopherson
2021-07-15 19:08 ` Dave Hansen
2021-07-15 19:18 ` Sean Christopherson
2021-07-07 18:35 ` [PATCH Part2 RFC v4 07/40] x86/sev: Split the physmap when adding the page in RMP table Brijesh Singh
2021-07-14 22:25 ` Sean Christopherson
2021-07-15 17:05 ` Brijesh Singh
2021-07-15 17:51 ` Sean Christopherson
2021-07-15 18:14 ` Brijesh Singh
2021-07-15 18:39 ` Sean Christopherson
2021-07-15 19:38 ` Brijesh Singh
2021-07-15 22:01 ` Sean Christopherson
2021-07-15 22:11 ` Brijesh Singh
2021-07-30 11:31 ` Vlastimil Babka
2021-07-30 16:10 ` Brijesh Singh [this message]
2021-07-07 18:35 ` [PATCH Part2 RFC v4 08/40] x86/traps: Define RMP violation #PF error code Brijesh Singh
2021-07-15 19:02 ` Sean Christopherson
2021-07-15 19:16 ` Dave Hansen
2021-07-07 18:35 ` [PATCH Part2 RFC v4 09/40] x86/fault: Add support to dump RMP entry on fault Brijesh Singh
2021-07-07 19:21 ` Dave Hansen
2021-07-08 15:02 ` Brijesh Singh
2021-07-08 15:30 ` Dave Hansen
2021-07-08 16:48 ` Brijesh Singh
2021-07-08 16:58 ` Dave Hansen
2021-07-08 17:11 ` Brijesh Singh
2021-07-08 17:15 ` Dave Hansen
2021-07-07 18:35 ` [PATCH Part2 RFC v4 10/40] x86/fault: Add support to handle the RMP fault for user address Brijesh Singh
2021-07-08 16:16 ` Dave Hansen
2021-07-12 15:43 ` Brijesh Singh
2021-07-12 16:00 ` Dave Hansen
2021-07-12 16:11 ` Brijesh Singh
2021-07-12 16:15 ` Dave Hansen
2021-07-12 16:24 ` Brijesh Singh
2021-07-12 16:29 ` Dave Hansen
2021-07-12 16:49 ` Brijesh Singh
2021-07-15 21:53 ` Sean Christopherson
2021-07-30 16:00 ` Vlastimil Babka
2021-07-30 16:31 ` Dave Hansen
2021-07-07 18:35 ` [PATCH Part2 RFC v4 11/40] crypto:ccp: Define the SEV-SNP commands Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 12/40] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 13/40] crypto: ccp: Shutdown SNP firmware on kexec Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 14/40] crypto:ccp: Provide APIs to issue SEV-SNP commands Brijesh Singh
2021-07-08 18:56 ` Dr. David Alan Gilbert
2021-07-07 18:35 ` [PATCH Part2 RFC v4 15/40] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled Brijesh Singh
2021-07-14 13:22 ` Marc Orr
2021-07-14 16:45 ` Brijesh Singh
2021-07-14 18:14 ` Marc Orr
2021-07-15 23:48 ` Sean Christopherson
2021-07-16 12:55 ` Brijesh Singh
2021-07-16 15:35 ` Sean Christopherson
2021-07-16 15:47 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 16/40] crypto: ccp: Handle the legacy SEV command " Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 17/40] crypto: ccp: Add the SNP_PLATFORM_STATUS command Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 18/40] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 19/40] crypto: ccp: provide APIs to query extended attestation report Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 20/40] KVM: SVM: Make AVIC backing, VMSA and VMCB memory allocation SNP safe Brijesh Singh
2021-07-14 13:35 ` Marc Orr
2021-07-14 16:47 ` Brijesh Singh
2021-07-20 18:02 ` Sean Christopherson
2021-08-03 14:38 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 21/40] KVM: SVM: Add initial SEV-SNP support Brijesh Singh
2021-07-16 18:00 ` Sean Christopherson
2021-07-16 18:46 ` Brijesh Singh
2021-07-16 19:31 ` Sean Christopherson
2021-07-16 21:03 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 22/40] KVM: SVM: Add KVM_SNP_INIT command Brijesh Singh
2021-07-16 19:33 ` Sean Christopherson
2021-07-16 21:25 ` Brijesh Singh
2021-07-19 20:24 ` Sean Christopherson
2021-07-07 18:35 ` [PATCH Part2 RFC v4 23/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command Brijesh Singh
2021-07-12 18:45 ` Peter Gonda
2021-07-16 19:43 ` Sean Christopherson
2021-07-16 21:42 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 24/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command Brijesh Singh
2021-07-16 20:01 ` Sean Christopherson
2021-07-16 22:00 ` Brijesh Singh
2021-07-19 20:51 ` Sean Christopherson
2021-07-19 21:34 ` Brijesh Singh
2021-07-19 21:36 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates Brijesh Singh
2021-07-16 20:09 ` Sean Christopherson
2021-07-16 22:16 ` Brijesh Singh
2021-07-17 0:46 ` Sean Christopherson
2021-07-19 12:55 ` Brijesh Singh
2021-07-19 17:18 ` Sean Christopherson
2021-07-19 18:34 ` Brijesh Singh
2021-07-19 19:03 ` Sean Christopherson
2021-07-19 19:14 ` Sean Christopherson
2021-07-19 19:37 ` Brijesh Singh
2021-07-20 16:40 ` Sean Christopherson
2021-07-20 18:23 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 26/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command Brijesh Singh
2021-07-16 20:18 ` Sean Christopherson
2021-07-16 22:48 ` Brijesh Singh
2021-07-19 16:54 ` Sean Christopherson
2021-07-19 18:29 ` Brijesh Singh
2021-07-19 19:14 ` Sean Christopherson
2021-07-19 19:49 ` Brijesh Singh
2021-07-19 20:13 ` Sean Christopherson
2021-07-21 17:53 ` Marc Orr
2021-07-07 18:36 ` [PATCH Part2 RFC v4 27/40] KVM: X86: Add kvm_x86_ops to get the max page level for the TDP Brijesh Singh
2021-07-16 19:19 ` Sean Christopherson
2021-07-16 20:41 ` Brijesh Singh
2021-07-20 19:38 ` Sean Christopherson
2021-07-20 20:06 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 28/40] KVM: X86: Introduce kvm_mmu_map_tdp_page() for use by SEV Brijesh Singh
2021-07-16 18:15 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 29/40] KVM: X86: Introduce kvm_mmu_get_tdp_walk() for SEV-SNP use Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 30/40] KVM: X86: Define new RMP check related #NPF error bits Brijesh Singh
2021-07-16 20:22 ` Sean Christopherson
2021-07-17 0:34 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 31/40] KVM: X86: update page-fault trace to log the 64-bit error code Brijesh Singh
2021-07-16 20:25 ` Sean Christopherson
2021-07-17 0:35 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 32/40] KVM: SVM: Add support to handle GHCB GPA register VMGEXIT Brijesh Singh
2021-07-16 20:45 ` Sean Christopherson
2021-07-17 0:44 ` Brijesh Singh
2021-07-19 20:04 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 33/40] KVM: SVM: Add support to handle MSR based Page State Change VMGEXIT Brijesh Singh
2021-07-16 21:00 ` Sean Christopherson
2021-07-19 14:19 ` Brijesh Singh
2021-07-19 18:55 ` Sean Christopherson
2021-07-19 19:15 ` Brijesh Singh
2021-08-13 16:32 ` Borislav Petkov
2021-07-07 18:36 ` [PATCH Part2 RFC v4 34/40] KVM: SVM: Add support to handle " Brijesh Singh
2021-07-16 21:14 ` Sean Christopherson
2021-07-19 14:24 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 35/40] KVM: Add arch hooks to track the host write to guest memory Brijesh Singh
2021-07-19 23:30 ` Sean Christopherson
2021-07-20 15:15 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 36/40] KVM: X86: Export the kvm_zap_gfn_range() for the SNP use Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 37/40] KVM: SVM: Add support to handle the RMP nested page fault Brijesh Singh
2021-07-20 0:10 ` Sean Christopherson
2021-07-20 17:55 ` Brijesh Singh
2021-07-20 22:31 ` Sean Christopherson
2021-07-20 23:53 ` Brijesh Singh
2021-07-21 20:15 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 38/40] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event Brijesh Singh
2021-07-19 22:50 ` Sean Christopherson
2021-07-20 14:37 ` Brijesh Singh
2021-07-20 16:28 ` Sean Christopherson
2021-07-20 18:21 ` Brijesh Singh
2021-07-20 22:09 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 39/40] KVM: SVM: Use a VMSA physical address variable for populating VMCB Brijesh Singh
2021-07-21 0:20 ` Sean Christopherson
2021-07-21 16:26 ` Tom Lendacky
2021-07-07 18:36 ` [PATCH Part2 RFC v4 40/40] KVM: SVM: Support SEV-SNP AP Creation NAE event Brijesh Singh
2021-07-21 0:01 ` Sean Christopherson
2021-07-21 17:47 ` Tom Lendacky
2021-07-21 19:52 ` Sean Christopherson
2021-08-20 14:44 ` Tom Lendacky
2021-07-08 15:40 ` [PATCH Part2 RFC v4 00/40] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Dave Hansen
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