From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> To: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org> Cc: Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>, "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>, Varun Sethi <Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>, David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org> Subject: Re: [PATCH v6 6/8] dma-mapping: detect and configure IOMMU in of_dma_configure Date: Tue, 16 Dec 2014 13:08:15 +0100 [thread overview] Message-ID: <2447060.c0PHi7y3cP@wuerfel> (raw) In-Reply-To: <20141215180933.GW20738-5wv7dgnIgG8@public.gmane.org> On Monday 15 December 2014 18:09:33 Will Deacon wrote: > > Using a single domain is a bit of a waste of resources in my case, so an > > evolution would be to create four domains and assign devices to them based on > > a policy. The policy could be fixed (round-robin for instance), or > > configurable (possibly through DT, although it's really a policy, not a > > hardware description). I think in case of the ARM SMMU, we concluded that the grouping is indeed best done in DT, because of there is no good algorithmic way to come up with a set of bitmasks that make up a proper grouping into domains. > I think having one default domain, which is home to all of the masters that > don't have any DMA restrictions is a good use of the hardware. That then > leaves you with three domains to cover VFIO, devices with DMA limitations > and potentially device isolation (if we had a way to describe that). Yes, I agree. There are also a number of degrees to which one might want to enable IOMMUs at boot time: - force-disable: use swiotlb only and turn off all IOMMUs or program them with a static linear mapping if they cannot be disabled in hardware - soft-enable: use IOMMUs only for devices whose dma-mask does not cover all the physical memory. This would provide the highest performance - force-enable: use the IOMMU for any device that has an 'iommus' property, to catch any wild DMA pointer accesses. - secure-enable: like force-enable, but use as many separate domains as possible to provide isolation between devices as well. Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v6 6/8] dma-mapping: detect and configure IOMMU in of_dma_configure Date: Tue, 16 Dec 2014 13:08:15 +0100 [thread overview] Message-ID: <2447060.c0PHi7y3cP@wuerfel> (raw) In-Reply-To: <20141215180933.GW20738@arm.com> On Monday 15 December 2014 18:09:33 Will Deacon wrote: > > Using a single domain is a bit of a waste of resources in my case, so an > > evolution would be to create four domains and assign devices to them based on > > a policy. The policy could be fixed (round-robin for instance), or > > configurable (possibly through DT, although it's really a policy, not a > > hardware description). I think in case of the ARM SMMU, we concluded that the grouping is indeed best done in DT, because of there is no good algorithmic way to come up with a set of bitmasks that make up a proper grouping into domains. > I think having one default domain, which is home to all of the masters that > don't have any DMA restrictions is a good use of the hardware. That then > leaves you with three domains to cover VFIO, devices with DMA limitations > and potentially device isolation (if we had a way to describe that). Yes, I agree. There are also a number of degrees to which one might want to enable IOMMUs at boot time: - force-disable: use swiotlb only and turn off all IOMMUs or program them with a static linear mapping if they cannot be disabled in hardware - soft-enable: use IOMMUs only for devices whose dma-mask does not cover all the physical memory. This would provide the highest performance - force-enable: use the IOMMU for any device that has an 'iommus' property, to catch any wild DMA pointer accesses. - secure-enable: like force-enable, but use as many separate domains as possible to provide isolation between devices as well. Arnd
next prev parent reply other threads:[~2014-12-16 12:08 UTC|newest] Thread overview: 220+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-12-01 16:57 [PATCH v6 0/8] Introduce automatic DMA configuration for IOMMU masters Will Deacon 2014-12-01 16:57 ` Will Deacon [not found] ` <1417453034-21379-1-git-send-email-will.deacon-5wv7dgnIgG8@public.gmane.org> 2014-12-01 16:57 ` [PATCH v6 1/8] iommu: provide early initialisation hook for IOMMU drivers Will Deacon 2014-12-01 16:57 ` Will Deacon [not found] ` <1417453034-21379-2-git-send-email-will.deacon-5wv7dgnIgG8@public.gmane.org> 2014-12-01 23:54 ` Rob Herring 2014-12-01 23:54 ` Rob Herring [not found] ` <CAL_JsqKHvh9KSTYrrs1Pts5Kg=8dA1V6NiW57_2vdDH173qQGg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-02 9:23 ` Marek Szyprowski 2014-12-02 9:23 ` Marek Szyprowski [not found] ` <547D84F4.8030204-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> 2014-12-02 9:36 ` Arnd Bergmann 2014-12-02 9:36 ` Arnd Bergmann 2014-12-02 9:43 ` Will Deacon 2014-12-02 9:43 ` Will Deacon 2014-12-02 12:05 ` Thierry Reding 2014-12-02 12:05 ` Thierry Reding 2014-12-02 14:16 ` Grant Likely 2014-12-02 14:16 ` Grant Likely [not found] ` <CACxGe6vyMkyE9ZRj_FQzi19ESEo7OV_RQoVV65xBYpdQV8cRGQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-03 19:57 ` Arnd Bergmann 2014-12-03 19:57 ` Arnd Bergmann 2014-12-04 9:49 ` Will Deacon 2014-12-04 9:49 ` Will Deacon [not found] ` <20141204094953.GA13224-5wv7dgnIgG8@public.gmane.org> 2014-12-04 10:10 ` Arnd Bergmann 2014-12-04 10:10 ` Arnd Bergmann 2014-12-04 10:21 ` Will Deacon 2014-12-04 10:21 ` Will Deacon [not found] ` <20141204102127.GF13224-5wv7dgnIgG8@public.gmane.org> 2014-12-04 11:19 ` Arnd Bergmann 2014-12-04 11:19 ` Arnd Bergmann 2014-12-04 11:25 ` Grant Likely 2014-12-04 11:25 ` Grant Likely [not found] ` <CACxGe6v4ZVHHGcc3Lhp8+FgKakyCkJFRAT2ufj-3DGWa=wmGkA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-04 11:52 ` Will Deacon 2014-12-04 11:52 ` Will Deacon [not found] ` <20141204115254.GF14519-5wv7dgnIgG8@public.gmane.org> 2014-12-04 12:43 ` Grant Likely 2014-12-04 12:43 ` Grant Likely 2014-12-04 12:26 ` Robin Murphy 2014-12-04 12:26 ` Robin Murphy [not found] ` <54805312.6000402-5wv7dgnIgG8@public.gmane.org> 2014-12-04 12:42 ` Grant Likely 2014-12-04 12:42 ` Grant Likely [not found] ` <CACxGe6uR5J4Cjdh_xYhBPoQRgeYwHPv5=AnuRmQKSD3yZrMK9Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-04 13:43 ` Robin Murphy 2014-12-04 13:43 ` Robin Murphy [not found] ` <54806504.20507-5wv7dgnIgG8@public.gmane.org> 2014-12-04 13:58 ` Grant Likely 2014-12-04 13:58 ` Grant Likely 2014-12-04 14:49 ` Thierry Reding 2014-12-04 14:49 ` Thierry Reding [not found] ` <20141204144925.GB31464-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2014-12-04 17:42 ` Robin Murphy 2014-12-04 17:42 ` Robin Murphy [not found] ` <54809D09.2050406-5wv7dgnIgG8@public.gmane.org> 2014-12-04 17:58 ` Grant Likely 2014-12-04 17:58 ` Grant Likely [not found] ` <CACxGe6tpFHdP1-5NWiNVAqzXx-diN1xfRbu0AQDyVJ6AU_4RXg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-04 19:42 ` Robin Murphy 2014-12-04 19:42 ` Robin Murphy [not found] ` <5480B924.2010205-5wv7dgnIgG8@public.gmane.org> 2014-12-05 12:10 ` Will Deacon 2014-12-05 12:10 ` Will Deacon [not found] ` <20141205121037.GI1630-5wv7dgnIgG8@public.gmane.org> 2014-12-05 12:21 ` Arnd Bergmann 2014-12-05 12:21 ` Arnd Bergmann 2014-12-05 12:35 ` Robin Murphy 2014-12-05 12:35 ` Robin Murphy [not found] ` <5481A688.4030606-5wv7dgnIgG8@public.gmane.org> 2014-12-05 13:06 ` Grant Likely 2014-12-05 13:06 ` Grant Likely [not found] ` <CACxGe6vppOQj-hJnqEEtLwDuSr4bzcbTgEFj8=x4ULu=yxswpg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-05 13:18 ` Thierry Reding 2014-12-05 13:18 ` Thierry Reding [not found] ` <20141205131815.GA18747-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2014-12-05 13:21 ` Grant Likely 2014-12-05 13:21 ` Grant Likely [not found] ` <CACxGe6vqstoCBiJ7TLvhNt+40TUJRB2ORoRKKtorhM-ETHXu0A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-05 13:31 ` Thierry Reding 2014-12-05 13:31 ` Thierry Reding 2014-12-05 13:49 ` Marek Szyprowski 2014-12-05 13:49 ` Marek Szyprowski 2014-12-04 12:51 ` Arnd Bergmann 2014-12-04 12:51 ` Arnd Bergmann 2014-12-02 10:30 ` Pantelis Antoniou 2014-12-02 10:30 ` Pantelis Antoniou 2014-12-01 16:57 ` [PATCH v6 2/8] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops Will Deacon 2014-12-01 16:57 ` Will Deacon [not found] ` <1417453034-21379-3-git-send-email-will.deacon-5wv7dgnIgG8@public.gmane.org> 2014-12-01 22:58 ` Rob Herring 2014-12-01 22:58 ` Rob Herring [not found] ` <CAL_JsqLtN3euwXHM4BzYxkXsgE=Dmn05aXzL+kr_8x23voneZA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-02 9:16 ` Arnd Bergmann 2014-12-02 9:16 ` Arnd Bergmann 2014-12-01 16:57 ` [PATCH v6 3/8] iommu: add new iommu_ops callback for adding an OF device Will Deacon 2014-12-01 16:57 ` Will Deacon 2014-12-01 16:57 ` [PATCH v6 4/8] iommu: provide helper function to configure an IOMMU for an of master Will Deacon 2014-12-01 16:57 ` Will Deacon 2014-12-01 16:57 ` [PATCH v6 5/8] iommu: fix initialization without 'add_device' callback Will Deacon 2014-12-01 16:57 ` Will Deacon 2014-12-01 16:57 ` [PATCH v6 6/8] dma-mapping: detect and configure IOMMU in of_dma_configure Will Deacon 2014-12-01 16:57 ` Will Deacon [not found] ` <1417453034-21379-7-git-send-email-will.deacon-5wv7dgnIgG8@public.gmane.org> 2014-12-01 23:06 ` Rob Herring 2014-12-01 23:06 ` Rob Herring 2014-12-10 14:52 ` Rob Clark 2014-12-10 14:52 ` Rob Clark [not found] ` <CAF6AEGs6dZauq1QxY_OqBPUs0xHYjjGTi+H7Vm-mNvJtmTAHRA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-10 15:08 ` Will Deacon 2014-12-10 15:08 ` Will Deacon [not found] ` <20141210150853.GH23639-5wv7dgnIgG8@public.gmane.org> 2014-12-10 15:54 ` Robin Murphy 2014-12-10 15:54 ` Robin Murphy [not found] ` <54886CA2.3040406-5wv7dgnIgG8@public.gmane.org> 2014-12-10 15:56 ` Laurent Pinchart 2014-12-10 15:56 ` Laurent Pinchart 2014-12-14 15:49 ` Laurent Pinchart 2014-12-14 15:49 ` Laurent Pinchart 2014-12-14 15:59 ` Laurent Pinchart 2014-12-14 15:59 ` Laurent Pinchart 2014-12-15 17:10 ` Will Deacon 2014-12-15 17:10 ` Will Deacon 2014-12-15 16:40 ` Will Deacon 2014-12-15 16:40 ` Will Deacon [not found] ` <20141215164041.GN20738-5wv7dgnIgG8@public.gmane.org> 2014-12-15 17:16 ` Laurent Pinchart 2014-12-15 17:16 ` Laurent Pinchart 2014-12-15 18:09 ` Will Deacon 2014-12-15 18:09 ` Will Deacon [not found] ` <20141215180933.GW20738-5wv7dgnIgG8@public.gmane.org> 2014-12-16 12:08 ` Arnd Bergmann [this message] 2014-12-16 12:08 ` Arnd Bergmann 2014-12-17 12:09 ` Will Deacon 2014-12-17 12:09 ` Will Deacon [not found] ` <20141217120948.GB870-5wv7dgnIgG8@public.gmane.org> 2014-12-17 14:15 ` Arnd Bergmann 2014-12-17 14:15 ` Arnd Bergmann 2014-12-17 14:45 ` Will Deacon 2014-12-17 14:45 ` Will Deacon 2014-12-17 15:35 ` Arnd Bergmann 2014-12-17 15:35 ` Arnd Bergmann 2014-12-17 17:17 ` Will Deacon 2014-12-17 17:17 ` Will Deacon [not found] ` <20141217171752.GB30307-5wv7dgnIgG8@public.gmane.org> 2014-12-17 19:48 ` Arnd Bergmann 2014-12-17 19:48 ` Arnd Bergmann 2014-12-21 10:04 ` Will Deacon 2014-12-21 10:04 ` Will Deacon [not found] ` <20141221100451.GA23242-5wv7dgnIgG8@public.gmane.org> 2014-12-22 13:36 ` Arnd Bergmann 2014-12-22 13:36 ` Arnd Bergmann 2015-01-07 18:57 ` Will Deacon 2015-01-07 18:57 ` Will Deacon [not found] ` <20150107185704.GV7485-5wv7dgnIgG8@public.gmane.org> 2015-01-07 19:29 ` Arnd Bergmann 2015-01-07 19:29 ` Arnd Bergmann 2015-01-08 10:53 ` Will Deacon 2015-01-08 10:53 ` Will Deacon 2014-12-17 14:27 ` Robin Murphy 2014-12-17 14:27 ` Robin Murphy [not found] ` <549192D2.10008-5wv7dgnIgG8@public.gmane.org> 2014-12-17 15:01 ` Will Deacon 2014-12-17 15:01 ` Will Deacon [not found] ` <20141217150158.GF870-5wv7dgnIgG8@public.gmane.org> 2014-12-17 15:38 ` Arnd Bergmann 2014-12-17 15:38 ` Arnd Bergmann 2014-12-17 17:20 ` Will Deacon 2014-12-17 17:20 ` Will Deacon 2014-12-17 0:05 ` Laurent Pinchart 2014-12-17 0:05 ` Laurent Pinchart 2014-12-14 15:51 ` Laurent Pinchart 2014-12-14 15:51 ` Laurent Pinchart 2014-12-15 11:32 ` Will Deacon 2014-12-15 11:32 ` Will Deacon [not found] ` <20141215113252.GH20738-5wv7dgnIgG8@public.gmane.org> 2014-12-17 0:19 ` Laurent Pinchart 2014-12-17 0:19 ` Laurent Pinchart 2014-12-17 11:14 ` Will Deacon 2014-12-17 11:14 ` Will Deacon 2014-12-01 16:57 ` [PATCH v6 7/8] arm: call iommu_init before of_platform_populate Will Deacon 2014-12-01 16:57 ` Will Deacon 2014-12-01 16:57 ` [PATCH v6 8/8] arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops Will Deacon 2014-12-01 16:57 ` Will Deacon [not found] ` <1417453034-21379-9-git-send-email-will.deacon-5wv7dgnIgG8@public.gmane.org> 2015-01-14 9:00 ` Alexandre Courbot 2015-01-14 9:00 ` Alexandre Courbot [not found] ` <54B63028.3090701-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> 2015-01-14 10:46 ` Will Deacon 2015-01-14 10:46 ` Will Deacon 2015-01-14 13:51 ` Heiko Stübner 2015-01-14 13:51 ` Heiko Stübner 2015-01-14 19:17 ` Will Deacon 2015-01-14 19:17 ` Will Deacon [not found] ` <20150114191749.GL4050-5wv7dgnIgG8@public.gmane.org> 2015-01-15 8:30 ` Thierry Reding 2015-01-15 8:30 ` Thierry Reding 2015-01-15 11:13 ` Will Deacon 2015-01-15 11:13 ` Will Deacon [not found] ` <20150114104610.GC4050-5wv7dgnIgG8@public.gmane.org> 2015-01-15 2:57 ` Alexandre Courbot 2015-01-15 2:57 ` Alexandre Courbot 2015-01-15 8:28 ` Thierry Reding 2015-01-15 8:28 ` Thierry Reding 2015-01-15 11:12 ` Will Deacon 2015-01-15 11:12 ` Will Deacon [not found] ` <20150115111211.GF23475-5wv7dgnIgG8@public.gmane.org> 2015-01-15 23:18 ` Laurent Pinchart 2015-01-15 23:18 ` Laurent Pinchart 2015-01-18 6:54 ` Alexandre Courbot 2015-01-18 6:54 ` Alexandre Courbot [not found] ` <54BB58AA.5070407-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> 2015-01-18 11:18 ` Laurent Pinchart 2015-01-18 11:18 ` Laurent Pinchart 2015-01-19 11:12 ` Will Deacon 2015-01-19 11:12 ` Will Deacon [not found] ` <20150119111202.GD32131-5wv7dgnIgG8@public.gmane.org> 2015-01-19 11:34 ` Laurent Pinchart 2015-01-19 11:34 ` Laurent Pinchart 2015-01-19 12:31 ` Thierry Reding 2015-01-19 12:31 ` Thierry Reding [not found] ` <20150119123058.GA7312-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2015-01-20 15:14 ` Laurent Pinchart 2015-01-20 15:14 ` Laurent Pinchart 2015-01-20 15:19 ` Will Deacon 2015-01-20 15:19 ` Will Deacon [not found] ` <20150120151910.GD1549-5wv7dgnIgG8@public.gmane.org> 2015-01-20 15:21 ` Will Deacon 2015-01-20 15:21 ` Will Deacon 2015-01-20 15:35 ` Laurent Pinchart 2015-01-20 15:35 ` Laurent Pinchart 2015-01-19 12:43 ` Thierry Reding 2015-01-19 12:43 ` Thierry Reding [not found] ` <20150119124305.GC7312-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2015-01-19 12:50 ` Will Deacon 2015-01-19 12:50 ` Will Deacon [not found] ` <20150119125051.GI32131-5wv7dgnIgG8@public.gmane.org> 2015-01-19 13:36 ` Thierry Reding 2015-01-19 13:36 ` Thierry Reding [not found] ` <20150119133633.GA23778-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2015-01-20 13:50 ` Laurent Pinchart 2015-01-20 13:50 ` Laurent Pinchart 2015-01-19 16:13 ` Arnd Bergmann 2015-01-19 16:13 ` Arnd Bergmann 2015-01-20 16:41 ` Laurent Pinchart 2015-01-20 16:41 ` Laurent Pinchart 2015-01-19 12:36 ` Thierry Reding 2015-01-19 12:36 ` Thierry Reding [not found] ` <20150119123623.GB7312-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2015-01-19 15:52 ` Arnd Bergmann 2015-01-19 15:52 ` Arnd Bergmann 2015-01-19 16:21 ` Thierry Reding 2015-01-19 16:21 ` Thierry Reding [not found] ` <20150119162111.GA7751-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2015-01-19 17:02 ` Arnd Bergmann 2015-01-19 17:02 ` Arnd Bergmann 2015-01-20 13:47 ` Laurent Pinchart 2015-01-20 13:47 ` Laurent Pinchart 2015-01-19 12:49 ` Thierry Reding 2015-01-19 12:49 ` Thierry Reding [not found] ` <20150119124934.GD7312-AwZRO8vwLAwmlAP/+Wk3EA@public.gmane.org> 2015-01-20 14:05 ` Laurent Pinchart 2015-01-20 14:05 ` Laurent Pinchart 2014-12-05 7:12 ` [PATCH v6 0/8] Introduce automatic DMA configuration for IOMMU masters Olof Johansson 2014-12-05 7:12 ` Olof Johansson [not found] ` <CAOesGMg9BpL3AyDjuAvH_H5fOm-uga+_CZuJZ5p8zpHpJLg0qA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-12-05 12:11 ` Will Deacon 2014-12-05 12:11 ` Will Deacon 2014-12-15 0:24 ` [PATCH/RFC] iommu/ipmmu-vmsa: Use DT-based instantiation Laurent Pinchart 2014-12-15 0:24 ` Laurent Pinchart
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=2447060.c0PHi7y3cP@wuerfel \ --to=arnd-r2ngtmty4d4@public.gmane.org \ --cc=Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org \ --cc=dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org \ --cc=iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org \ --cc=jroedel-l3A5Bk7waGM@public.gmane.org \ --cc=laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org \ --cc=linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org \ --cc=thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \ --cc=will.deacon-5wv7dgnIgG8@public.gmane.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: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.