* vIOMMU&IOMMU gIOVA to HPA mapping
@ 2022-11-14 12:31 leohou
2022-11-14 16:18 ` Alex Williamson
0 siblings, 1 reply; 2+ messages in thread
From: leohou @ 2022-11-14 12:31 UTC (permalink / raw)
To: virtualization, iommu, qemu-arm, jasowang; +Cc: leohou1402
Hi，
Here is my application scenario：
1. The NIC (Network Information Center) passes through to the VM(Virtual Machine);
2. The VM uses the user mode driver DPDK;
Question:
1. vIOMMU maintains the mapping gIOVA->gPA, When do you use this gPA ?
2. Physical IOMMU maintains the GIOVA->HPA mapping ? If so, by what means (gIOVA -> HPA) mapping ?
3. What does QEMU do in NIC pass-through address translation ？
---------------------------------------------------------------------------------------------------------------------
_____________________________________________________________________________
| ___________________________________________________________ |
| | _____________________________________________________ | |
| | | | | |
| | | __________________________________ | | |
| | | | ______ | | | | ______
| | | User | | Mem |-----------------------|----|-|----|-----> | |
| | | | |______| DPDK | | | | (gVA) |______|
| | | | (gVA) | | | | | |
| | | |______|___________________________| | | | | |
| | |--GuestOS----------|--------------------------------| | | | |
| | | ______\/__________________________ | | | | |
| | VM | | VFIO | | | | | |
| User | | Kernel |___________ __________________| | | | | |
| | | | vfio-pci | | | | | | | |
| | | | (gIOVA) | | vfio_iommu_type2 | | | | | |
Software | | | |______|____|___|__________________| | | | | |
| | |___________________|________________________________| | | | |
| | ____________________________________________________ | | | |
| | | ______|____ __________________ | | | \/ \/
| | | | \/ | | | | | | ______
| | | | NIC | | vIOMMU | | | | | |
| | | QEMU | Instance | | --|----|-|----|-----> |______|
| | | | (gIOVA) | | (GIOVA-->GPA) | | | | (gPA) | |
| | | |_____|_____| |__________________| | | | | |
| | |__________________|_________________________________| | | | |
| |_______________________|___________________________________| | | |
|---HostOS---------------------------|----------------------------------------| | |
| ___________________________________________________________ | | |
| | | | | | |
| | | VFIO | | | |
| Kernel |_______________________|_____ _________________________| | | |
| | \/ | | | | | |
| | vfio-pci | | vfio_iommu_type1 | | | |
| | | | | | | | |
| |_______________________|_____|___|_________________________| | | |
|____________________________________|________________________________________| | |
-----------------------------------------------|-------------------------------------------------|----|--------------
____________________________________\/____ _________________________ ___\/___\/___________
| | | | | | | | |
Hardware | NIC | DMA (gIOVA) --|---|-> IOMMU --|---------|->|______| |
| |_____________________________| | (gIOVA-->HPA) | (HPA) | Physical Memory |
|__________________________________________| |_________________________| |_____________________|
---------------------------------------------------------------------------------------------------------------------
leohou@tom.com
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: vIOMMU&IOMMU gIOVA to HPA mapping
2022-11-14 12:31 vIOMMU&IOMMU gIOVA to HPA mapping leohou
@ 2022-11-14 16:18 ` Alex Williamson
0 siblings, 0 replies; 2+ messages in thread
From: Alex Williamson @ 2022-11-14 16:18 UTC (permalink / raw)
To: leohou@tom.com; +Cc: virtualization, iommu, qemu-arm, jasowang, leohou1402
On Mon, 14 Nov 2022 20:31:49 +0800
"leohou@tom.com" <leohou@tom.com> wrote:
> Hi，
> Here is my application scenario：
> 1. The NIC (Network Information Center) passes through to the VM(Virtual Machine);
> 2. The VM uses the user mode driver DPDK;
>
> Question:
> 1. vIOMMU maintains the mapping gIOVA->gPA, When do you use this gPA ?
QEMU in the host derives the hVA from the gPA. The vIOMMU driver in
QEMU is triggering the gIOVA to hVA mapping through vfio in the host.
> 2. Physical IOMMU maintains the GIOVA->HPA mapping ? If so, by what means (gIOVA -> HPA) mapping ?
As above, the vIOMMU in the guest provides gIOVA -> gPA, in QEMU we do
the gPA -> hVA, then vfio in the host kernel performs hVA -> hPA via
page pinning.
> 3. What does QEMU do in NIC pass-through address translation ？
The guest visible vIOMMU triggers MemoryListener notifications in QEMU
for the device address space, which insert and removes mappings to the
vfio layer below it. Thanks,
Alex
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