Re: [PATCH] iommu/amd: Fix extended features logging

[Joe Perches]

(cc'ing the printk maintainers)

On Sun, 2021-04-11 at 00:11 +0300, Alexander Monakov wrote:
> print_iommu_info prints the EFR register and then the decoded list of
> features on a separate line:
> 
> pci 0000:00:00.2: AMD-Vi: Extended features (0x206d73ef22254ade):
>  PPR X2APIC NX GT IA GA PC GA_vAPIC
> 
> The second line is emitted via 'pr_cont', which causes it to have a
> different ('warn') loglevel compared to the previous line ('info').
> 
> Commit 9a295ff0ffc9 attempted to rectify this by removing the newline
> from the pci_info format string, but this doesn't work, as pci_info
> calls implicitly append a newline anyway.
> 
> Restore the newline, and call pr_info with empty format string to set
> the loglevel for subsequent pr_cont calls. The same solution is used in
> EFI and uvesafb drivers.
> 
> Fixes: 9a295ff0ffc9 ("iommu/amd: Print extended features in one line to fix divergent log levels")
> Signed-off-by: Alexander Monakov <amonakov@xxxxxxxxx>
> Cc: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
> Cc: Joerg Roedel <jroedel@xxxxxxx>
> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
> ---
>  drivers/iommu/amd/init.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index 596d0c413473..a25e241eff1c 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -1929,8 +1929,11 @@ static void print_iommu_info(void)
>  		pci_info(pdev, "Found IOMMU cap 0x%hx\n", iommu->cap_ptr);
>  
> 
>  		if (iommu->cap & (1 << IOMMU_CAP_EFR)) {
> -			pci_info(pdev, "Extended features (%#llx):",
> +			pci_info(pdev, "Extended features (%#llx):\n",
>  				 iommu->features);
> +
> +			pr_info("");
> +
>  			for (i = 0; i < ARRAY_SIZE(feat_str); ++i) {
>  				if (iommu_feature(iommu, (1ULL << i)))
>  					pr_cont(" %s", feat_str[i]);

This shouldn't be necessary.
If this is true then a lot of output logging code broke.