Re: [PATCH v4 12/15] irqchip/gic-v3-its: Share ITS tables with a non-trusted hypervisor

Will Deacon
2024-07-10T13:17:39Z

On Mon, Jul 01, 2024 at 10:55:02AM +0100, Steven Price wrote:
> Within a realm guest the ITS is emulated by the host. This means the
> allocations must have been made available to the host by a call to
> set_memory_decrypted(). Introduce an allocation function which performs
> this extra call.
>
> For the ITT use a custom genpool-based allocator that calls
> set_memory_decrypted() for each page allocated, but then suballocates
> the size needed for each ITT. Note that there is no mechanism
> implemented to return pages from the genpool, but it is unlikely the
> peak number of devices will so much larger than the normal level - so
> this isn't expected to be an issue.
>
> Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> Changes since v3:
> * Use BIT() macro.
> * Use a genpool based allocator in its_create_device() to avoid
> allocating a full page.
> * Fix subject to drop "realm" and use gic-v3-its.
> * Add error handling to ITS alloc/free.
> Changes since v2:
> * Drop 'shared' from the new its_xxx function names as they are used
> for non-realm guests too.
> * Don't handle the NUMA_NO_NODE case specially - alloc_pages_node()
> should do the right thing.
> * Drop a pointless (void *) cast.
> ---
> drivers/irqchip/irq-gic-v3-its.c | 139 ++++++++++++++++++++++++++-----
> 1 file changed, 116 insertions(+), 23 deletions(-)

I gave this (and the following patch) a spin in a protected guest under
pKVM and was able to use MSIs for my virtio devices, so:

Tested-by: Will Deacon <will@kernel.org>

Will