linux-kernel - Re: [PATCH RFCv1 0/7] vfio: Allow userspace to specify the address for each MSI vector

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZzPOsrbkmztWZ4U/@Asurada-Nvidia>
Date: Tue, 12 Nov 2024 13:54:58 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Robin Murphy <robin.murphy@....com>
CC: <maz@...nel.org>, <tglx@...utronix.de>, <bhelgaas@...gle.com>,
	<alex.williamson@...hat.com>, <jgg@...dia.com>, <leonro@...dia.com>,
	<shameerali.kolothum.thodi@...wei.com>, <dlemoal@...nel.org>,
	<kevin.tian@...el.com>, <smostafa@...gle.com>,
	<andriy.shevchenko@...ux.intel.com>, <reinette.chatre@...el.com>,
	<eric.auger@...hat.com>, <ddutile@...hat.com>, <yebin10@...wei.com>,
	<brauner@...nel.org>, <apatel@...tanamicro.com>,
	<shivamurthy.shastri@...utronix.de>, <anna-maria@...utronix.de>,
	<nipun.gupta@....com>, <marek.vasut+renesas@...lbox.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: Re: [PATCH RFCv1 0/7] vfio: Allow userspace to specify the address
 for each MSI vector

On Mon, Nov 11, 2024 at 01:09:20PM +0000, Robin Murphy wrote:
> On 2024-11-09 5:48 am, Nicolin Chen wrote:
> > To solve this problem the VMM should capture the MSI IOVA allocated by the
> > guest kernel and relay it to the GIC driver in the host kernel, to program
> > the correct MSI IOVA. And this requires a new ioctl via VFIO.
> 
> Once VFIO has that information from userspace, though, do we really need
> the whole complicated dance to push it right down into the irqchip layer
> just so it can be passed back up again? AFAICS
> vfio_msi_set_vector_signal() via VFIO_DEVICE_SET_IRQS already explicitly
> rewrites MSI-X vectors, so it seems like it should be pretty
> straightforward to override the message address in general at that
> level, without the lower layers having to be aware at all, no?

Didn't see that clearly!! It works with a simple following override:
--------------------------------------------------------------------
@@ -497,6 +497,10 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev,
                struct msi_msg msg;

                get_cached_msi_msg(irq, &msg);
+               if (vdev->msi_iovas) {
+                       msg.address_lo = lower_32_bits(vdev->msi_iovas[vector]);
+                       msg.address_hi = upper_32_bits(vdev->msi_iovas[vector]);
+               }
                pci_write_msi_msg(irq, &msg);
        }
 
--------------------------------------------------------------------

With that, I think we only need one VFIO change for this part :)

Thanks!
Nicolin