[PATCH] RISC-V: KVM: Fix compilation without RISCV_ISA_ZICBOM

[Palmer Dabbelt]

On Mon, 10 Oct 2022 02:40:29 PDT (-0700), ajones at ventanamicro.com wrote:
> Fix undefined reference of riscv_cbom_block_size when compiling KVM
> without RISCV_ISA_ZICBOM. Note, RISCV_ISA_ZICBOM is a sufficient
> guard as it selects RISCV_DMA_NONCOHERENT, which is needed to compile
> dma-noncoherent.c (which is the file where riscv_cbom_block_size and
> its initializer live).
>
> Fixes: afd5dde9a186 ("RISC-V: KVM: Provide UAPI for Zicbom block size")
> Reported-by: kernel test robot <lkp at intel.com>
> Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
> ---
>  arch/riscv/kvm/vcpu.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index a032c4f0d600..e4453caba728 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -265,11 +265,13 @@ static int kvm_riscv_vcpu_get_reg_config(struct kvm_vcpu *vcpu,
>  	case KVM_REG_RISCV_CONFIG_REG(isa):
>  		reg_val = vcpu->arch.isa[0] & KVM_RISCV_BASE_ISA_MASK;
>  		break;
> +#ifdef CONFIG_RISCV_ISA_ZICBOM
>  	case KVM_REG_RISCV_CONFIG_REG(zicbom_block_size):
>  		if (!riscv_isa_extension_available(vcpu->arch.isa, ZICBOM))
>  			return -EINVAL;
>  		reg_val = riscv_cbom_block_size;
>  		break;
> +#endif
>  	default:
>  		return -EINVAL;
>  	}

Thanks, looks like this is tripping up the kernelci builds too: 
https://linux.kernelci.org/build/id/6343b37c6fd2dcbb5dcab5f3/logs/ .  
This symbol is actually a bit odd, as we don't actually just use it 
under Zicbom because of the T-Head stuff.  Looks like that's generically 
broken, though, so IMO we need something like this

diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 6cb7d96ad9c7..fba86fa3a628 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -5,6 +5,9 @@

 #include <asm/cacheflush.h>

+unsigned int riscv_cbom_block_size;
+EXPORT_SYMBOL(riscv_cbom_block_size);
+
 #ifdef CONFIG_SMP

 #include <asm/sbi.h>
diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
index e3f9bdf47c5f..33d21ace0971 100644
--- a/arch/riscv/mm/dma-noncoherent.c
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -12,7 +12,6 @@
 #include <linux/of_device.h>
 #include <asm/cacheflush.h>

-unsigned int riscv_cbom_block_size;
 static bool noncoherent_supported;

 void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,

which should be

Fixes: 8f7e001e0325 ("RISC-V: Clean up the Zicbom block size probing").

We might also want the ifdef for KVM, as that would allow us to build KVM that
doesn't support these VCPU configurations, but that's sort of a different
question.