From: David Hildenbrand <david@redhat.com>
To: Matthew Rosato <mjrosato@linux.ibm.com>, qemu-s390x@nongnu.org
Cc: farman@linux.ibm.com, schnelle@linux.ibm.com, thuth@redhat.com,
pasic@linux.ibm.com, borntraeger@linux.ibm.com,
richard.henderson@linaro.org, iii@linux.ibm.com, clg@redhat.com,
qemu-devel@nongnu.org
Subject: Re: [PATCH v5 1/2] s390x/pci: add support for guests that request direct mapping
Date: Thu, 27 Feb 2025 13:02:27 +0100 [thread overview]
Message-ID: <b02ecb38-039e-48aa-9407-67cc43a5b7e7@redhat.com> (raw)
In-Reply-To: <20250226210013.238349-2-mjrosato@linux.ibm.com>
On 26.02.25 22:00, Matthew Rosato wrote:
> When receiving a guest mpcifc(4) or mpcifc(6) instruction without the T
> bit set, treat this as a request to perform direct mapping instead of
> address translation. In order to facilitate this, pin the entirety of
> guest memory into the host iommu.
>
> Pinning for the direct mapping case is handled via vfio and its memory
> listener. Additionally, ram discard settings are inherited from vfio:
> coordinated discards (e.g. virtio-mem) are allowed while uncoordinated
> discards (e.g. virtio-balloon) are disabled.
>
> Subsequent guest DMA operations are all expected to be of the format
> guest_phys+sdma, allowing them to be used as lookup into the host
> iommu table.
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2025-02-27 12:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-26 21:00 [PATCH v5 0/2] s390x/pci: relax I/O address translation requirement Matthew Rosato
2025-02-26 21:00 ` [PATCH v5 1/2] s390x/pci: add support for guests that request direct mapping Matthew Rosato
2025-02-27 12:02 ` David Hildenbrand [this message]
2025-02-26 21:00 ` [PATCH v5 2/2] s390x/pci: indicate QEMU supports relaxed translation for passthrough Matthew Rosato
2025-03-06 7:08 ` [PATCH v5 0/2] s390x/pci: relax I/O address translation requirement Thomas Huth
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