From: Vlastimil Babka <vbabka@suse.cz>
To: Brijesh Singh <brijesh.singh@amd.com>, Peter Gonda <pgonda@google.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@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>,
Sean Christopherson <seanjc@google.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 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>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Andi Kleen <ak@linux.intel.com>,
tony.luck@intel.com, marcorr@google.com,
sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support
Date: Mon, 22 Nov 2021 18:03:40 +0100 [thread overview]
Message-ID: <6e67f74a-fb4e-fda4-9583-dad28f14ed3a@suse.cz> (raw)
In-Reply-To: <daf5066b-e89b-d377-ed8a-9338f1a04c0d@amd.com>
On 11/22/21 16:23, Brijesh Singh wrote:
> Hi Peter,
>
> On 11/12/21 9:43 AM, Peter Gonda wrote:
>> Hi Brijesh,,
>>
>> One high level discussion I'd like to have on these SNP KVM patches.
>>
>> In these patches (V5) if a host userspace process writes a guest
>> private page a SIGBUS is issued to that process. If the kernel writes
>> a guest private page then the kernel panics due to the unhandled RMP
>> fault page fault. This is an issue because not all writes into guest
>> memory may come from a bug in the host. For instance a malicious or
>> even buggy guest could easily point the host to writing a private page
>> during the emulation of many virtual devices (virtio, NVMe, etc). For
>> example if a well behaved guests behavior is to: start up a driver,
>> select some pages to share with the guest, ask the host to convert
>> them to shared, then use those pages for virtual device DMA, if a
>> buggy guest forget the step to request the pages be converted to
>> shared its easy to see how the host could rightfully write to private
>> memory. I think we can better guarantee host reliability when running
>> SNP guests without changing SNP’s security properties.
>>
>> Here is an alternative to the current approach: On RMP violation (host
>> or userspace) the page fault handler converts the page from private to
>> shared to allow the write to continue. This pulls from s390’s error
>> handling which does exactly this. See ‘arch_make_page_accessible()’.
>> Additionally it adds less complexity to the SNP kernel patches, and
>> requires no new ABI.
>>
>> In the current (V5) KVM implementation if a userspace process
>> generates an RMP violation (writes to guest private memory) the
>> process receives a SIGBUS. At first glance, it would appear that
>> user-space shouldn’t write to private memory. However, guaranteeing
>> this in a generic fashion requires locking the RMP entries (via locks
>> external to the RMP). Otherwise, a user-space process emulating a
>> guest device IO may be vulnerable to having the guest memory
>> (maliciously or by guest bug) converted to private while user-space
>> emulation is happening. This results in a well behaved userspace
>> process receiving a SIGBUS.
>>
>> This proposal allows buggy and malicious guests to run under SNP
>> without jeopardizing the reliability / safety of host processes. This
>> is very important to a cloud service provider (CSP) since it’s common
>> to have host wide daemons that write/read all guests, i.e. a single
>> process could manage the networking for all VMs on the host. Crashing
>> that singleton process kills networking for all VMs on the system.
>>
> Thank you for starting the thread; based on the discussion, I am keeping the
> current implementation as-is and *not* going with the auto conversion from
> private to shared. To summarize what we are doing in the current SNP series:
>
> - If userspace accesses guest private memory, it gets SIGBUS.
So, is there anything protecting host userspace processes from malicious guests?
> - If kernel accesses[*] guest private memory, it does panic.
>
> [*] Kernel consults the RMP table for the page ownership before the access.
> If the page is shared, then it uses the locking mechanism to ensure that a
> guest will not be able to change the page ownership while kernel has it mapped.
>
> thanks
>
next prev parent reply other threads:[~2021-11-22 17:03 UTC|newest]
Thread overview: 239+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-20 15:58 [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 01/45] x86/cpufeatures: Add SEV-SNP CPU feature Brijesh Singh
2021-09-16 16:56 ` Borislav Petkov
2021-09-16 17:35 ` Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 02/45] iommu/amd: Introduce function to check SEV-SNP support Brijesh Singh
2021-09-16 17:26 ` Borislav Petkov
2021-08-20 15:58 ` [PATCH Part2 v5 03/45] x86/sev: Add the host SEV-SNP initialization support Brijesh Singh
2021-09-24 8:58 ` Borislav Petkov
2021-08-20 15:58 ` [PATCH Part2 v5 04/45] x86/sev: Add RMP entry lookup helpers Brijesh Singh
2021-09-24 9:49 ` Borislav Petkov
2021-09-27 16:01 ` Brijesh Singh
2021-09-27 16:04 ` Brijesh Singh
2021-09-29 12:56 ` Borislav Petkov
2022-06-02 11:57 ` Jarkko Sakkinen
2021-08-20 15:58 ` [PATCH Part2 v5 05/45] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction Brijesh Singh
2021-09-24 14:04 ` Borislav Petkov
2021-09-27 16:06 ` Brijesh Singh
2021-10-15 18:05 ` Sean Christopherson
2021-10-15 20:18 ` Brijesh Singh
2021-10-15 20:27 ` Sean Christopherson
2021-10-15 20:36 ` Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 06/45] x86/sev: Invalid pages from direct map when adding it to RMP table Brijesh Singh
2021-09-29 14:34 ` Borislav Petkov
2021-09-30 16:19 ` Brijesh Singh
2021-10-01 11:06 ` Borislav Petkov
2021-08-20 15:58 ` [PATCH Part2 v5 07/45] x86/traps: Define RMP violation #PF error code Brijesh Singh
2021-09-29 17:25 ` Borislav Petkov
2021-08-20 15:58 ` [PATCH Part2 v5 08/45] x86/fault: Add support to handle the RMP fault for user address Brijesh Singh
2021-08-23 14:20 ` Dave Hansen
2021-08-23 14:36 ` Brijesh Singh
2021-08-23 14:50 ` Dave Hansen
2021-08-24 16:42 ` Joerg Roedel
2021-08-25 9:16 ` Vlastimil Babka
2021-08-25 13:50 ` Tom Lendacky
2021-09-29 18:19 ` Borislav Petkov
2021-08-20 15:58 ` [PATCH Part2 v5 09/45] x86/fault: Add support to dump RMP entry on fault Brijesh Singh
2021-09-29 18:38 ` Borislav Petkov
2021-08-20 15:58 ` [PATCH Part2 v5 10/45] crypto: ccp: shutdown SEV firmware on kexec Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 11/45] crypto:ccp: Define the SEV-SNP commands Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 12/45] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 13/45] crypto:ccp: Provide APIs to issue SEV-SNP commands Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 14/45] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled Brijesh Singh
2022-02-25 18:03 ` Alper Gun
2022-03-01 14:12 ` Brijesh Singh
2022-06-14 0:10 ` Alper Gun
2021-08-20 15:58 ` [PATCH Part2 v5 15/45] crypto: ccp: Handle the legacy SEV command " Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 16/45] crypto: ccp: Add the SNP_PLATFORM_STATUS command Brijesh Singh
2021-09-10 3:18 ` Marc Orr
2021-09-13 11:17 ` Brijesh Singh
2021-09-22 17:35 ` Dr. David Alan Gilbert
2021-09-23 18:01 ` Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 17/45] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command Brijesh Singh
2021-09-01 21:02 ` Connor Kuehl
2021-09-01 23:06 ` Brijesh Singh
2021-09-10 3:27 ` Marc Orr
2021-09-13 11:29 ` Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 18/45] crypto: ccp: Provide APIs to query extended attestation report Brijesh Singh
2021-09-10 3:30 ` Marc Orr
2021-09-12 7:46 ` Dov Murik
2021-08-20 15:58 ` [PATCH Part2 v5 19/45] KVM: SVM: Add support to handle AP reset MSR protocol Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 20/45] KVM: SVM: Provide the Hypervisor Feature support VMGEXIT Brijesh Singh
2021-10-12 20:38 ` Sean Christopherson
2021-08-20 15:58 ` [PATCH Part2 v5 21/45] KVM: SVM: Make AVIC backing, VMSA and VMCB memory allocation SNP safe Brijesh Singh
2021-09-22 18:55 ` Dr. David Alan Gilbert
2021-09-23 18:09 ` Brijesh Singh
2021-09-23 18:39 ` Dr. David Alan Gilbert
2021-09-23 22:23 ` Brijesh Singh
2021-09-23 19:17 ` Marc Orr
2021-09-23 20:44 ` Brijesh Singh
2021-09-23 20:55 ` Marc Orr
2021-10-12 20:44 ` Sean Christopherson
2021-08-20 15:58 ` [PATCH Part2 v5 22/45] KVM: SVM: Add initial SEV-SNP support Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 23/45] KVM: SVM: Add KVM_SNP_INIT command Brijesh Singh
2021-09-05 6:56 ` Dov Murik
2021-09-05 13:59 ` Brijesh Singh
2021-09-10 3:32 ` Marc Orr
2021-09-13 11:32 ` Brijesh Singh
2021-09-16 15:50 ` Peter Gonda
2022-06-13 20:58 ` Alper Gun
2022-06-13 23:15 ` Ashish Kalra
2022-06-13 23:33 ` Alper Gun
2022-06-14 0:21 ` Ashish Kalra
2022-06-14 15:37 ` Peter Gonda
2022-06-14 16:11 ` Kalra, Ashish
2022-06-14 16:30 ` Peter Gonda
2022-06-14 17:16 ` Kalra, Ashish
2022-06-14 18:58 ` Alper Gun
2022-06-14 20:23 ` Kalra, Ashish
2022-06-14 20:29 ` Peter Gonda
2022-06-14 20:39 ` Kalra, Ashish
2021-08-20 15:58 ` [PATCH Part2 v5 24/45] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command Brijesh Singh
2021-08-20 15:58 ` [PATCH Part2 v5 25/45] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command Brijesh Singh
2021-09-27 16:43 ` Peter Gonda
2021-09-27 19:33 ` Brijesh Singh
2021-10-05 15:01 ` Peter Gonda
2021-08-20 15:58 ` [PATCH Part2 v5 26/45] KVM: SVM: Mark the private vma unmerable for SEV-SNP guests Brijesh Singh
2021-09-23 17:18 ` Dr. David Alan Gilbert
2021-10-12 18:46 ` Sean Christopherson
2021-10-13 12:39 ` Brijesh Singh
2021-10-13 14:34 ` Sean Christopherson
2021-10-13 14:51 ` Brijesh Singh
2021-10-13 15:33 ` Sean Christopherson
2021-08-20 15:59 ` [PATCH Part2 v5 27/45] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command Brijesh Singh
2022-05-18 20:21 ` Marc Orr
2022-05-18 20:35 ` Kalra, Ashish
2021-08-20 15:59 ` [PATCH Part2 v5 28/45] KVM: X86: Keep the NPT and RMP page level in sync Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 29/45] KVM: x86/mmu: Move 'pfn' variable to caller of direct_page_fault() Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 30/45] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX and SNP Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 31/45] KVM: x86: Introduce kvm_mmu_get_tdp_walk() for SEV-SNP use Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 32/45] KVM: x86: Define RMP page fault error bits for #NPF Brijesh Singh
2021-09-30 23:41 ` Marc Orr
2021-10-01 13:03 ` Borislav Petkov
2021-08-20 15:59 ` [PATCH Part2 v5 33/45] KVM: x86: Update page-fault trace to log full 64-bit error code Brijesh Singh
2021-10-13 21:23 ` Sean Christopherson
2021-08-20 15:59 ` [PATCH Part2 v5 34/45] KVM: SVM: Do not use long-lived GHCB map while setting scratch area Brijesh Singh
2021-10-13 21:20 ` Sean Christopherson
2021-10-15 16:11 ` Brijesh Singh
2021-10-15 16:44 ` Sean Christopherson
2021-08-20 15:59 ` [PATCH Part2 v5 35/45] KVM: SVM: Remove the long-lived GHCB host map Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 36/45] KVM: SVM: Add support to handle GHCB GPA register VMGEXIT Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 37/45] KVM: SVM: Add support to handle MSR based Page State Change VMGEXIT Brijesh Singh
2021-09-28 9:56 ` Dr. David Alan Gilbert
2021-10-12 21:48 ` Sean Christopherson
2021-10-13 17:04 ` Sean Christopherson
2021-10-13 17:05 ` Brijesh Singh
2021-10-13 17:24 ` Sean Christopherson
2021-10-13 17:49 ` Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 38/45] KVM: SVM: Add support to handle " Brijesh Singh
2021-09-28 10:17 ` Dr. David Alan Gilbert
2021-09-28 23:20 ` Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 39/45] KVM: SVM: Introduce ops for the post gfn map and unmap Brijesh Singh
2021-10-13 0:23 ` Sean Christopherson
2021-10-13 18:10 ` Brijesh Singh
2021-10-13 20:10 ` Sean Christopherson
2021-10-13 21:49 ` Brijesh Singh
2021-10-13 22:10 ` Sean Christopherson
2021-10-13 22:31 ` Brijesh Singh
2021-10-13 20:16 ` Sean Christopherson
2021-10-15 16:31 ` Brijesh Singh
2021-10-15 17:16 ` Sean Christopherson
2022-09-08 21:21 ` Michael Roth
2022-09-08 22:28 ` Michael Roth
2022-09-14 8:05 ` Sean Christopherson
2022-09-14 11:02 ` Marc Orr
2022-09-14 16:15 ` Sean Christopherson
2022-09-14 16:32 ` Marc Orr
2022-09-14 16:39 ` Marc Orr
2022-09-19 17:56 ` Michael Roth
2021-08-20 15:59 ` [PATCH Part2 v5 40/45] KVM: x86: Export the kvm_zap_gfn_range() for the SNP use Brijesh Singh
2021-08-20 15:59 ` [PATCH Part2 v5 41/45] KVM: SVM: Add support to handle the RMP nested page fault Brijesh Singh
2021-09-29 12:24 ` Dr. David Alan Gilbert
2021-10-13 17:57 ` Sean Christopherson
2021-08-20 15:59 ` [PATCH Part2 v5 42/45] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event Brijesh Singh
2021-09-29 21:33 ` Peter Gonda
2021-09-29 22:00 ` Peter Gonda
2021-08-20 15:59 ` [PATCH Part2 v5 43/45] KVM: SVM: Use a VMSA physical address variable for populating VMCB Brijesh Singh
2021-10-15 18:58 ` Sean Christopherson
2021-08-20 15:59 ` [PATCH Part2 v5 44/45] KVM: SVM: Support SEV-SNP AP Creation NAE event Brijesh Singh
2021-10-15 19:50 ` Sean Christopherson
2021-10-20 21:48 ` Brijesh Singh
2021-10-20 23:01 ` Sean Christopherson
2021-08-20 15:59 ` [PATCH Part2 v5 45/45] KVM: SVM: Add module parameter to enable the SEV-SNP Brijesh Singh
2021-11-12 15:43 ` [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Peter Gonda
2021-11-12 17:59 ` Dave Hansen
2021-11-12 18:35 ` Borislav Petkov
2021-11-12 19:48 ` Sean Christopherson
2021-11-12 20:04 ` Borislav Petkov
2021-11-12 20:37 ` Sean Christopherson
2021-11-12 20:53 ` Borislav Petkov
2021-11-12 21:12 ` Peter Gonda
2021-11-12 21:20 ` Andy Lutomirski
2021-11-12 22:04 ` Borislav Petkov
2021-11-12 22:52 ` Peter Gonda
2021-11-13 0:00 ` Sean Christopherson
2021-11-13 0:10 ` Marc Orr
2021-11-13 18:34 ` Sean Christopherson
2021-11-14 7:54 ` Marc Orr
2021-11-15 17:16 ` Sean Christopherson
2021-11-15 16:36 ` Joerg Roedel
2021-11-15 17:25 ` Sean Christopherson
2021-11-12 21:30 ` Marc Orr
2021-11-12 21:37 ` Dave Hansen
2021-11-12 21:40 ` Marc Orr
2021-11-12 21:39 ` Andy Lutomirski
2021-11-12 21:43 ` Marc Orr
2021-11-12 22:54 ` Peter Gonda
2021-11-13 0:53 ` Sean Christopherson
2021-11-13 1:04 ` Marc Orr
2021-11-13 18:28 ` Sean Christopherson
2021-11-14 7:41 ` Marc Orr
2021-11-15 18:17 ` Sean Christopherson
2021-11-15 16:52 ` Joerg Roedel
2021-11-15 16:18 ` Brijesh Singh
2021-11-15 18:44 ` Sean Christopherson
2021-11-15 18:58 ` Brijesh Singh
2021-11-12 21:16 ` Marc Orr
2021-11-12 21:23 ` Andy Lutomirski
2021-11-12 21:35 ` Borislav Petkov
2021-11-15 12:30 ` Dr. David Alan Gilbert
2021-11-15 14:42 ` Joerg Roedel
2021-11-15 15:33 ` Dr. David Alan Gilbert
2021-11-15 16:20 ` Joerg Roedel
2021-11-15 16:32 ` Dr. David Alan Gilbert
2021-11-15 18:26 ` Sean Christopherson
2021-11-15 18:41 ` Marc Orr
2021-11-15 19:15 ` Sean Christopherson
2021-11-16 3:07 ` Marc Orr
2021-11-16 5:14 ` Andy Lutomirski
2021-11-16 13:21 ` Joerg Roedel
2021-11-16 18:26 ` Sean Christopherson
2021-11-16 18:39 ` Peter Gonda
2021-11-16 13:30 ` Joerg Roedel
2021-11-16 5:00 ` Andy Lutomirski
2021-11-16 13:02 ` Joerg Roedel
2021-11-16 20:08 ` Sean Christopherson
2021-11-15 16:16 ` Joerg Roedel
2021-11-22 15:23 ` Brijesh Singh
2021-11-22 17:03 ` Vlastimil Babka [this message]
2021-11-22 18:01 ` Brijesh Singh
2021-11-22 18:30 ` Dave Hansen
2021-11-22 19:06 ` Brijesh Singh
2021-11-22 19:14 ` Dave Hansen
2021-11-22 20:33 ` Brijesh Singh
2021-11-22 21:34 ` Sean Christopherson
2021-11-22 22:51 ` Dave Hansen
2021-11-23 5:15 ` Luck, Tony
2021-11-23 7:18 ` Borislav Petkov
2021-11-23 15:36 ` Sean Christopherson
2021-11-23 16:26 ` Borislav Petkov
2021-11-23 8:55 ` Vlastimil Babka
2021-11-24 16:03 ` Joerg Roedel
2021-11-24 17:48 ` Dave Hansen
2021-11-24 19:34 ` Vlastimil Babka
2021-11-25 10:05 ` Joerg Roedel
2021-11-29 14:44 ` Brijesh Singh
2021-11-29 14:58 ` Vlastimil Babka
2021-11-29 16:13 ` Brijesh Singh
2021-11-30 19:40 ` Vlastimil Babka
2021-11-29 16:41 ` Dave Hansen
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