linux-kernel - RE: [PATCH v2] PCI: hv: Replace retarget_msi_interrupt_params with hyperv_pcpu_input

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Message-ID: <SA1PR21MB13352587E3078F61A4DA1BE9BF609@SA1PR21MB1335.namprd21.prod.outlook.com>
Date:   Fri, 21 Apr 2023 02:08:05 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "kw@...ux.com" <kw@...ux.com>, "robh@...nel.org" <robh@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] PCI: hv: Replace retarget_msi_interrupt_params with
 hyperv_pcpu_input_arg

> From: Dexuan Cui <decui@...rosoft.com>
> Sent: Thursday, April 20, 2023 6:30 PM
> ...
> 4 commits are involved here:
> A (2016): commit 0de8ce3ee8e3 ("PCI: hv: Allocate physically contiguous
> hypercall params buffer")
> B (2017): commit be66b6736591 ("PCI: hv: Use page allocation for hbus
> structure")
> C (2019): commit 877b911a5ba0 ("PCI: hv: Avoid a kmemleak false positive
> caused by the hbus buffer")
> D (2018): commit 68bb7bfb7985 ("X86/Hyper-V: Enable IPI enlightenments")
> 
> Patch D introduced the per-CPU hypercall input page
> "hyperv_pcpu_input_arg"
> in 2018. With patch D, we no longer need the per-Hyper-V-PCI-bus hypercall
> input page "hbus->retarget_msi_interrupt_params" that was added in patch
> A,
> and the issue addressed by patch B is no longer an issue, and we can also
> get rid of patch C.
> 
> The change here is required for PCI device assignment to work for
> Confidential VMs (CVMs) running without a paravisor, because otherwise we
> would have to call set_memory_decrypted() for
> "hbus->retarget_msi_interrupt_params" before calling the hypercall
> HVCALL_RETARGET_INTERRUPT.
> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
> ---
> 
> Changes in v2:
>   Fixed the inaccuracy in the commit message (Thanks Michael):
>     "Confidential VMs (CVMs)" -> "Confidential VMs (CVMs) running
> without a paravisor".
> 
>   Added Michael's Reviewed-by.

Hi Bjorn, Lorenzo, since this change is pure Hyper-V stuff, I'd like it to
go through the hyper-v tree if you have no objection.

The hyper-v tree already has a PCI patch from Michael:
https://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux.git/commit/?h=hyperv-next&id=2c6ba4216844ca7918289b49ed5f3f7138ee2402

My patch won't apply cleanly without Michael's patch, because we
both changed "struct hv_pcibus_device".

Thanks,
Dexuan