Re: [PATCH kvmtool 1/1] riscv: pci: Add --force-pci option for riscv VMs.

[Alexandru Elisei <alexandru.elisei@arm.com>]

Hi,

CC'ing the kvmtool maintainers and other people that might be interested in this
thread. Sorry for hijacking your patch!

On Wed, Jan 18, 2023 at 05:20:07PM +0000, Rajnesh Kanwal wrote:
> Adding force-pci option to allow forcing virtio
> devices to use pci as the default transport.

arm is in the same situation, MMIO is the default virtio transport. I was bitten
by that in the past. It also cought other people unaware, and I remember maz
complaining about it on the list.

So I was thinking about adding a new command line parameter, --virtio-transport,
with the possible values mmio-legacy, mmio, pci-legacy and pci. Then each
architecture can define the default value for the transport. For arm, that would
be pci.

What do you guys think?

Thanks,
Alex

> 
> Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
> ---
>  riscv/include/kvm/kvm-arch.h        | 6 ++++--
>  riscv/include/kvm/kvm-config-arch.h | 7 ++++++-
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/riscv/include/kvm/kvm-arch.h b/riscv/include/kvm/kvm-arch.h
> index 1e130f5..2cf41c5 100644
> --- a/riscv/include/kvm/kvm-arch.h
> +++ b/riscv/include/kvm/kvm-arch.h
> @@ -46,8 +46,10 @@
>  
>  #define KVM_VM_TYPE		0
>  
> -#define VIRTIO_DEFAULT_TRANS(kvm) \
> -	((kvm)->cfg.virtio_legacy ? VIRTIO_MMIO_LEGACY : VIRTIO_MMIO)
> +#define VIRTIO_DEFAULT_TRANS(kvm)					\
> +	((kvm)->cfg.arch.virtio_trans_pci ?				\
> +	 ((kvm)->cfg.virtio_legacy ? VIRTIO_PCI_LEGACY : VIRTIO_PCI) :	\
> +	 ((kvm)->cfg.virtio_legacy ? VIRTIO_MMIO_LEGACY : VIRTIO_MMIO))
>  
>  #define VIRTIO_RING_ENDIAN	VIRTIO_ENDIAN_LE
>  
> diff --git a/riscv/include/kvm/kvm-config-arch.h b/riscv/include/kvm/kvm-config-arch.h
> index 188125c..901a5e0 100644
> --- a/riscv/include/kvm/kvm-config-arch.h
> +++ b/riscv/include/kvm/kvm-config-arch.h
> @@ -6,6 +6,7 @@
>  struct kvm_config_arch {
>  	const char	*dump_dtb_filename;
>  	bool		ext_disabled[KVM_RISCV_ISA_EXT_MAX];
> +	bool		virtio_trans_pci;
>  };
>  
>  #define OPT_ARCH_RUN(pfx, cfg)						\
> @@ -26,6 +27,10 @@ struct kvm_config_arch {
>  		    "Disable Zicbom Extension"),			\
>  	OPT_BOOLEAN('\0', "disable-zihintpause",			\
>  		    &(cfg)->ext_disabled[KVM_RISCV_ISA_EXT_ZIHINTPAUSE],\
> -		    "Disable Zihintpause Extension"),
> +		    "Disable Zihintpause Extension"),			\
> +	OPT_BOOLEAN('\0', "force-pci",					\
> +			&(cfg)->virtio_trans_pci,			\
> +		    "Force virtio devices to use PCI as their "		\
> +		    "default transport"),
>  
>  #endif /* KVM__KVM_CONFIG_ARCH_H */
> -- 
> 2.25.1
>