Re: [PATCH 1/2] s390: uv: Fix sysfs max number of VCPUs reporting

Christian Borntraeger
2021-01-19T10:11:55Z

On 19.01.21 11:04, Janosch Frank wrote:
> The number reported by the query is N-1 and I think people reading the
> sysfs file would expect N instead. For users creating VMs there's no
> actual difference because KVM's limit is currently below the UV's
> limit.
>
> The naming of the field is a bit misleading. Number in this context is
> used like ID and starts at 0. The query field denotes the maximum
> number that can be put into the VCPU number field in the "create
> secure CPU" UV call.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Fixes: a0f60f8431999 ("s390/protvirt: Add sysfs firmware interface for Ultravisor information")
> Cc: stable@vger.kernel.org
> ---
> arch/s390/boot/uv.c | 2 +-
> arch/s390/include/asm/uv.h | 4 ++--
> arch/s390/kernel/uv.c | 2 +-
> 3 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/boot/uv.c b/arch/s390/boot/uv.c
> index a15c033f53ca..afb721082989 100644
> --- a/arch/s390/boot/uv.c
> +++ b/arch/s390/boot/uv.c
> @@ -35,7 +35,7 @@ void uv_query_info(void)
> uv_info.guest_cpu_stor_len = uvcb.cpu_stor_len;
> uv_info.max_sec_stor_addr = ALIGN(uvcb.max_guest_stor_addr, PAGE_SIZE);
> uv_info.max_num_sec_conf = uvcb.max_num_sec_conf;
> - uv_info.max_guest_cpus = uvcb.max_guest_cpus;
> + uv_info.max_guest_cpu_id = uvcb.max_guest_cpu_num;
> }
>
> #ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index 0325fc0469b7..c484c95ea142 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -96,7 +96,7 @@ struct uv_cb_qui {
> u32 max_num_sec_conf;
> u64 max_guest_stor_addr;
> u8 reserved88[158 - 136];
> - u16 max_guest_cpus;
> + u16 max_guest_cpu_num;

I think it would read better if we name this also max_guest_cpu_id.
Otherwise this looks good.