From: Isaku Yamahata <isaku.yamahata@gmail.com>
To: Michael Roth <michael.roth@amd.com>
Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev,
linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com,
hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com,
seanjc@google.com, vkuznets@redhat.com, jmattson@google.com,
luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com,
pgonda@google.com, peterz@infradead.org,
srinivas.pandruvada@linux.intel.com, rientjes@google.com,
dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de,
vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com,
tony.luck@intel.com, marcorr@google.com,
sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com,
dgilbert@redhat.com, jarkko@kernel.org, ashish.kalra@amd.com,
nikunj.dadhania@amd.com, isaku.yamahata@gmail.com
Subject: Re: [PATCH RFC v8 01/56] KVM: x86: Add 'fault_is_private' x86 op
Date: Fri, 17 Mar 2023 21:53:35 -0700 [thread overview]
Message-ID: <20230318045335.GD408922@ls.amr.corp.intel.com> (raw)
In-Reply-To: <20230220183847.59159-2-michael.roth@amd.com>
On Mon, Feb 20, 2023 at 12:37:52PM -0600,
Michael Roth <michael.roth@amd.com> wrote:
> This callback is used by the KVM MMU to check whether a #NPF was for a
> private GPA or not.
>
> In some cases the full 64-bit error code for the #NPF will be needed to
> make this determination, so also update kvm_mmu_do_page_fault() to
> accept the full 64-bit value so it can be plumbed through to the
> callback.
Here is a patch to change error code 64-bit.
From 428a676face7a06a90e59dca1c32941c9b6ee001 Mon Sep 17 00:00:00 2001
Message-Id: <428a676face7a06a90e59dca1c32941c9b6ee001.1679114841.git.isaku.yamahata@intel.com>
From: Isaku Yamahata <isaku.yamahata@intel.com>
Date: Fri, 17 Mar 2023 12:58:42 -0700
Subject: [PATCH 1/4] KVM: x86/mmu: Pass round full 64-bit error code for the
KVM page fault
In some cases the full 64-bit error code for the KVM page fault will be
needed to make this determination, so also update kvm_mmu_do_page_fault()
to accept the full 64-bit value so it can be plumbed through to the
callback.
The upper 32 bits of error code is discarded at kvm_mmu_page_fault()
by lower_32_bits(). Now it's passed down as full 64 bits. It turns out
that only FNAME(page_fault) depends on it. Move lower_32_bits() into
FNAME(page_fault).
The accesses of fault->error_code are as follows
- FNAME(page_fault): change to explicitly use lower_32_bits()
- kvm_tdp_page_fault(): explicit mask with PFERR_LEVEL_MASK
- kvm_mmu_page_fault(): explicit mask with PFERR_RSVD_MASK,
PFERR_NESTED_GUEST_PAGE
- mmutrace: changed u32 -> u64
- pgprintk(): change %x -> %llx
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
arch/x86/kvm/mmu.h | 2 +-
arch/x86/kvm/mmu/mmu.c | 7 +++----
arch/x86/kvm/mmu/mmu_internal.h | 4 ++--
arch/x86/kvm/mmu/mmutrace.h | 2 +-
arch/x86/kvm/mmu/paging_tmpl.h | 4 ++--
5 files changed, 9 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index de9c6b98c41b..4aaef2132b97 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -156,7 +156,7 @@ static inline void kvm_mmu_load_pgd(struct kvm_vcpu *vcpu)
}
kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
- u32 error_code, int max_level);
+ u64 error_code, int max_level);
/*
* Check if a given access (described through the I/D, W/R and U/S bits of a
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 960609d72dd6..0ec94c72895c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4860,7 +4860,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
static int nonpaging_page_fault(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
- pgprintk("%s: gva %llx error %x\n", __func__, fault->addr, fault->error_code);
+ pgprintk("%s: gva %llx error %llx\n", __func__, fault->addr, fault->error_code);
/* This path builds a PAE pagetable, we can map 2mb pages at maximum. */
fault->max_level = PG_LEVEL_2M;
@@ -4986,7 +4986,7 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
}
kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
- u32 error_code, int max_level)
+ u64 error_code, int max_level)
{
int r;
struct kvm_page_fault fault = (struct kvm_page_fault) {
@@ -6238,8 +6238,7 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
}
if (r == RET_PF_INVALID) {
- r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa,
- lower_32_bits(error_code), false);
+ r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, error_code, false);
if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm))
return -EIO;
}
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index aa0836191b5a..bb5709f1cb57 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -341,7 +341,7 @@ static inline bool is_nx_huge_page_enabled(struct kvm *kvm)
struct kvm_page_fault {
/* arguments to kvm_mmu_do_page_fault. */
const gpa_t addr;
- const u32 error_code;
+ const u64 error_code;
const bool prefetch;
/* Derived from error_code. */
@@ -427,7 +427,7 @@ enum {
};
static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
- u32 err, bool prefetch)
+ u64 err, bool prefetch)
{
struct kvm_page_fault fault = {
.addr = cr2_or_gpa,
diff --git a/arch/x86/kvm/mmu/mmutrace.h b/arch/x86/kvm/mmu/mmutrace.h
index 2d7555381955..2e77883c92f6 100644
--- a/arch/x86/kvm/mmu/mmutrace.h
+++ b/arch/x86/kvm/mmu/mmutrace.h
@@ -261,7 +261,7 @@ TRACE_EVENT(
TP_STRUCT__entry(
__field(int, vcpu_id)
__field(gpa_t, cr2_or_gpa)
- __field(u32, error_code)
+ __field(u64, error_code)
__field(u64 *, sptep)
__field(u64, old_spte)
__field(u64, new_spte)
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 594af2e1fd2f..cab6822709e2 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -791,7 +791,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
int r;
bool is_self_change_mapping;
- pgprintk("%s: addr %llx err %x\n", __func__, fault->addr, fault->error_code);
+ pgprintk("%s: addr %llx err %llx\n", __func__, fault->addr, fault->error_code);
WARN_ON_ONCE(fault->is_tdp);
/*
@@ -800,7 +800,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
* The bit needs to be cleared before walking guest page tables.
*/
r = FNAME(walk_addr)(&walker, vcpu, fault->addr,
- fault->error_code & ~PFERR_RSVD_MASK);
+ lower_32_bits(fault->error_code) & ~PFERR_RSVD_MASK);
/*
* The page is not mapped by the guest. Let the guest handle it.
--
2.25.1
--
Isaku Yamahata <isaku.yamahata@gmail.com>
next prev parent reply other threads:[~2023-03-18 4:53 UTC|newest]
Thread overview: 147+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-20 18:37 [PATCH RFC v8 00/56] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Michael Roth
2023-02-20 18:37 ` [PATCH RFC v8 01/56] KVM: x86: Add 'fault_is_private' x86 op Michael Roth
2023-03-01 10:25 ` Zhi Wang
2023-03-18 4:51 ` Isaku Yamahata
2023-03-20 17:46 ` Michael Roth
2023-03-18 4:53 ` Isaku Yamahata [this message]
2023-02-20 18:37 ` [PATCH RFC v8 02/56] KVM: x86: Add 'update_mem_attr' " Michael Roth
2023-03-18 4:56 ` Isaku Yamahata
2023-03-20 18:05 ` Michael Roth
2023-03-21 11:21 ` Zhi Wang
2023-03-22 1:58 ` Michael Roth
2023-03-23 18:17 ` Zhi Wang
2023-03-28 4:36 ` Michael Roth
2023-03-28 23:00 ` Zhi Wang
2023-03-29 23:50 ` Michael Roth
2023-02-20 18:37 ` [PATCH RFC v8 03/56] KVM: x86: Add platform hooks for private memory invalidations Michael Roth
2023-03-18 5:13 ` Isaku Yamahata
2023-03-20 18:09 ` Michael Roth
2023-02-20 18:37 ` [PATCH RFC v8 04/56] KVM: Add HVA range operator Michael Roth
2023-02-20 21:37 ` Zhi Wang
2023-03-27 0:34 ` Michael Roth
2023-04-04 14:40 ` Zhi Wang
2023-02-20 18:37 ` [PATCH RFC v8 05/56] KVM: SEV: Require KVM_PROTECTED_VM when AMD_MEM_ENCRYPT is enabled Michael Roth
2023-02-20 18:37 ` [PATCH RFC v8 06/56] KVM: Split out memory attribute xarray updates to helper function Michael Roth
2023-02-20 18:37 ` [PATCH RFC v8 07/56] KVM: SEV: Populate private memory fd during LAUNCH_UPDATE_DATA Michael Roth
2023-02-20 18:37 ` [PATCH RFC v8 08/56] KVM: SEV: Rename sev_{pin,unpin}_memory Michael Roth
2023-03-03 14:00 ` Vlastimil Babka
2023-03-06 11:01 ` Nikunj A. Dadhania
2023-02-20 18:38 ` [PATCH RFC v8 09/56] KVM: SEV: Handle memory backed by restricted memfd Michael Roth
2023-03-03 14:05 ` Vlastimil Babka
2023-03-06 11:03 ` Nikunj A. Dadhania
2023-02-20 18:38 ` [PATCH RFC v8 10/56] x86/cpufeatures: Add SEV-SNP CPU feature Michael Roth
2023-02-21 21:21 ` Sathyanarayanan Kuppuswamy
2023-02-22 23:27 ` Kalra, Ashish
2023-02-20 18:38 ` [PATCH RFC v8 11/56] x86/sev: Add the host SEV-SNP initialization support Michael Roth
2023-02-20 20:12 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 12/56] x86/sev: Add RMP entry lookup helpers Michael Roth
2023-03-03 15:28 ` Vlastimil Babka
2023-03-29 22:59 ` Michael Roth
2023-04-20 16:31 ` Vlastimil Babka
2023-02-20 18:38 ` [PATCH RFC v8 13/56] x86/fault: Add helper for dumping RMP entries Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 14/56] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 15/56] x86/sev: Invalidate pages from the direct map when adding them to the RMP table Michael Roth
2023-03-01 12:07 ` Tom Dohrmann
2023-03-01 16:15 ` Dave Hansen
2023-03-28 22:12 ` Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 16/56] x86/traps: Define RMP violation #PF error code Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 17/56] x86/fault: Add support to handle the RMP fault for user address Michael Roth
2023-03-01 16:21 ` Dave Hansen
2023-03-28 23:31 ` Michael Roth
2023-04-11 18:27 ` Dave Hansen
2023-03-03 15:31 ` Vlastimil Babka
2023-02-20 18:38 ` [PATCH RFC v8 18/56] x86/fault: fix handle_split_page_fault() to work with memfd backed pages Michael Roth
2023-02-20 19:57 ` Hugh Dickins
2023-02-20 20:31 ` Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 19/56] x86/fault: Return pfn from dump_pagetable() for SEV-specific fault handling Michael Roth
2023-02-20 21:13 ` Zhi Wang
2023-02-28 10:53 ` Wu Zongyong
2023-02-20 18:38 ` [PATCH RFC v8 20/56] crypto:ccp: Define the SEV-SNP commands Michael Roth
2023-04-17 14:54 ` Sabin Rapan
2023-02-20 18:38 ` [PATCH RFC v8 21/56] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 22/56] crypto:ccp: Provide API to issue SEV and SNP commands Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 23/56] crypto: ccp: Introduce snp leaked pages list Michael Roth
2023-03-03 15:54 ` Vlastimil Babka
2023-02-20 18:38 ` [PATCH RFC v8 24/56] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled Michael Roth
2023-02-21 9:28 ` Zhi Wang
2023-02-21 15:31 ` Kalra, Ashish
2023-02-21 21:15 ` Zhi Wang
2023-02-21 22:06 ` Kalra, Ashish
2023-02-20 18:38 ` [PATCH RFC v8 25/56] crypto: ccp: Handle the legacy SEV command " Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 26/56] crypto: ccp: Add the SNP_PLATFORM_STATUS command Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 27/56] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command Michael Roth
2023-02-22 12:32 ` Zhi Wang
2023-02-22 16:50 ` Tom Lendacky
2023-02-22 22:43 ` Kalra, Ashish
2023-02-23 6:38 ` Zhi Wang
2023-02-23 14:19 ` Tom Lendacky
2023-02-20 18:38 ` [PATCH RFC v8 28/56] crypto: ccp: Provide APIs to query extended attestation report Michael Roth
2023-02-22 20:24 ` Zhi Wang
2023-02-22 22:35 ` Kalra, Ashish
2023-02-23 8:14 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 29/56] KVM: SVM: Add support to handle AP reset MSR protocol Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 30/56] KVM: SVM: Provide the Hypervisor Feature support VMGEXIT Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 31/56] KVM: SVM: Make AVIC backing, VMSA and VMCB memory allocation SNP safe Michael Roth
2023-02-22 20:42 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 32/56] KVM: SVM: Add initial SEV-SNP support Michael Roth
2023-02-23 17:46 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 33/56] KVM: SVM: Add KVM_SNP_INIT command Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 34/56] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command Michael Roth
2023-02-23 21:41 ` Zhi Wang
2023-02-24 16:22 ` Tom Lendacky
2023-04-26 17:06 ` Sabin Rapan
2023-04-26 18:02 ` Tom Lendacky
2023-02-20 18:38 ` [PATCH RFC v8 35/56] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command Michael Roth
2023-02-24 11:55 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 36/56] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command Michael Roth
2023-03-24 14:40 ` Alexander Graf
2023-02-20 18:38 ` [PATCH RFC v8 37/56] KVM: X86: Keep the NPT and RMP page level in sync Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 38/56] KVM: x86: Define RMP page fault error bits for #NPF Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 39/56] KVM: SVM: Add support to handle GHCB GPA register VMGEXIT Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 40/56] KVM: SVM: Add KVM_EXIT_VMGEXIT Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 41/56] KVM: SVM: Add support to handle MSR based Page State Change VMGEXIT Michael Roth
2023-02-24 15:06 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 42/56] KVM: SVM: Add support to handle " Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 43/56] KVM: x86: Export the kvm_zap_gfn_range() for the SNP use Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 44/56] KVM: SVM: Add support to handle the RMP nested page fault Michael Roth
2023-02-28 19:11 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 45/56] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event Michael Roth
2023-02-24 11:01 ` Alexander Graf
2023-02-28 19:34 ` Zhi Wang
2023-04-17 13:05 ` Alexander Graf
2023-02-20 18:38 ` [PATCH RFC v8 46/56] KVM: SVM: Use a VMSA physical address variable for populating VMCB Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 47/56] KVM: SVM: Support SEV-SNP AP Creation NAE event Michael Roth
2023-02-24 12:37 ` Alexander Graf
2023-02-28 20:47 ` Zhi Wang
2023-03-01 21:14 ` Alexander Graf
2023-04-05 0:54 ` Michael Roth
2023-04-04 22:48 ` Michael Roth
2023-04-05 15:20 ` Tom Lendacky
2023-02-20 18:38 ` [PATCH RFC v8 48/56] KVM: SVM: Add SNP-specific handling for memory attribute updates Michael Roth
2023-03-01 23:37 ` Dave Hansen
2023-04-05 23:48 ` Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 49/56] KVM: SVM: Implement .fault_is_private callback for SNP Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 50/56] KVM: SEV: Handle restricted memory invalidations " Michael Roth
2023-03-01 10:41 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 51/56] KVM: SVM: Add module parameter to enable the SEV-SNP Michael Roth
2023-03-01 10:45 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 52/56] ccp: Add support to decrypt the page Michael Roth
2023-03-01 21:20 ` Zhi Wang
2023-03-02 5:59 ` Dov Murik
2023-03-02 14:33 ` Tom Lendacky
2023-03-02 21:11 ` Dov Murik
2023-02-20 18:38 ` [PATCH RFC v8 53/56] KVM: SVM: Make VMSAVE target area memory allocation SNP safe Michael Roth
2023-03-01 21:23 ` Zhi Wang
2023-02-20 18:38 ` [PATCH RFC v8 54/56] x86/sev: Add KVM commands for instance certs Michael Roth
2023-02-21 12:40 ` Dov Murik
2023-03-02 0:02 ` Zhi Wang
2023-03-02 1:41 ` Dionna Amalie Glaze
2023-03-02 11:27 ` Zhi Wang
2023-03-02 11:34 ` Dov Murik
2023-02-20 18:38 ` [PATCH RFC v8 55/56] x86/sev: Document KVM_SEV_SNP_{G,S}ET_CERTS Michael Roth
2023-02-20 18:38 ` [PATCH RFC v8 56/56] iommu/amd: Add IOMMU_SNP_SHUTDOWN support Michael Roth
2023-03-01 16:56 ` [PATCH RFC v8 00/56] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Dave Hansen
2023-03-01 22:59 ` Zhi Wang
2023-03-01 23:39 ` Dave Hansen
2023-08-03 18:27 ` Schander, Johanna 'Mimoja' Amelie
2023-08-04 1:01 ` Kalra, Ashish
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230318045335.GD408922@ls.amr.corp.intel.com \
--to=isaku.yamahata@gmail.com \
--cc=ak@linux.intel.com \
--cc=alpergun@google.com \
--cc=ardb@kernel.org \
--cc=ashish.kalra@amd.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=dgilbert@redhat.com \
--cc=dovmurik@linux.ibm.com \
--cc=hpa@zytor.com \
--cc=jarkko@kernel.org \
--cc=jmattson@google.com \
--cc=jroedel@suse.de \
--cc=kirill@shutemov.name \
--cc=kvm@vger.kernel.org \
--cc=linux-coco@lists.linux.dev \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=marcorr@google.com \
--cc=michael.roth@amd.com \
--cc=mingo@redhat.com \
--cc=nikunj.dadhania@amd.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=pgonda@google.com \
--cc=rientjes@google.com \
--cc=sathyanarayanan.kuppuswamy@linux.intel.com \
--cc=seanjc@google.com \
--cc=slp@redhat.com \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=tobin@ibm.com \
--cc=tony.luck@intel.com \
--cc=vbabka@suse.cz \
--cc=vkuznets@redhat.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).