On Tue, Mar 12, 2019 at 18:55:49 -0300, Daniel Henrique Barboza wrote:
> The NVLink2 support in QEMU implements the detection of NVLink2
> capable devices by verifying the attributes of the VFIO mem region
> QEMU allocates for the NVIDIA GPUs. To properly allocate an
> adequate amount of memLock, Libvirt needs this information before
> a QEMU instance is even created, thus querying QEMU is not
> possible and opening a VFIO window is too much.
>
> An alternative is presented in this patch. Making the following
> assumptions:
>
> - if we want GPU RAM to be available in the guest, an NVLink2 bridge
> must be passed through;
>
> - an unknown PCI device can be classified as a NVLink2 bridge
> if its device tree node has 'ibm,gpu', 'ibm,nvlink',
> 'ibm,nvlink-speed' and 'memory-region'.
>
> This patch introduces a helper called @ppc64VFIODeviceIsNV2Bridge
> that checks the device tree node of a given PCI device and
> check if it meets the criteria to be a NVLink2 bridge. This
> new function will be used in a follow-up patch that, using the
> first assumption, will set up the rlimits of the guest
> accordingly.
>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx>
> ---
> src/qemu/qemu_domain.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
disclaimer: This is a code review. I don't have much knowledge about
what you are trying to implement.
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 1659e88478..dcc92d253c 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -10398,6 +10398,35 @@ qemuDomainUpdateCurrentMemorySize(virDomainObjPtr vm)
> }
>
>
> +/**
> + * ppc64VFIODeviceIsNV2Bridge:
> + * @device: string with the PCI device address
> + *
> + * This function receives a string that represents a PCI device,
> + * such as '0004:04:00.0', and tells if the device is a NVLink2
> + * bridge.
> + */
> +static bool
> +ppc64VFIODeviceIsNV2Bridge(const char *device)
> +{
> + const char *nvlink2Files[] = {"ibm,gpu", "ibm,nvlink",
> + "ibm,nvlink-speed", "memory-region"};
> + char *file;
> + size_t i;
> +
> + for (i = 0; i < 4; i++) {
Use ARRAY_CARDINALITY(nvlink2Files) instead of '4'.
> + if ((virAsprintf(&file, "/sys/bus/pci/devices/%s/of_node/%s",
> + device, nvlink2Files[i])) < 0)
> + return false;
> +
> + if (!virFileExists(file))
> + return false;
memory allocated to 'file' is leaked in every loop and also at exit. You
can use VIR_AUTOFREE(char *) file above, but you need to free the
pointer also in every single loop.
> + }
> +
> + return true;
> +}
This function is unused and static, this means the build will fail after
this patch.
> +
> +
> /**
> * getPPC64MemLockLimitBytes:
> * @def: domain definition
> --
> 2.20.1
>
> --
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