Re: [PATCH] powerpc/pseries/vas: Don't print an error when VAS is unavailable

[Michael Ellerman]

Nicholas Piggin <npig...@gmail.com> writes:
> Excerpts from Cédric Le Goater's message of November 26, 2021 5:13 pm:
>> On 11/26/21 06:21, Nicholas Piggin wrote:
>>> KVM does not support VAS so guests always print a useless error on boot
>>> 
>>>      vas: HCALL(398) error -2, query_type 0, result buffer 0x57f2000
>>> 
>>> Change this to only print the message if the error is not H_FUNCTION.
>> 
>> 
>> Just being curious, why is it even called since "ibm,compression" should
>> not be exposed in the DT ?
>
> It looks like vas does not test for it. I guess in theory there can be 
> other functions than compression implemented as an accelerator. Maybe
> that's why?

Yeah I guess, or it's just not structured that well. The vas platform
code is a bit awkward, it's there to support drivers, but it's not
actually driver code.

I think we can probably rework it so the vas code does nothing until a
driver calls in to it.

eg. something like below.

cheers


diff --git a/arch/powerpc/platforms/pseries/vas.c 
b/arch/powerpc/platforms/pseries/vas.c
index b043e3936d21..dc3491fc919d 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -454,6 +454,8 @@ static const struct vas_user_win_ops vops_pseries = {
        .close_win      = vas_deallocate_window, /* Close window */
 };
 
+static int pseries_vas_init(void);
+
 /*
  * Supporting only nx-gzip coprocessor type now, but this API code
  * extended to other coprocessor types later.
@@ -463,7 +465,8 @@ int vas_register_api_pseries(struct module *mod, enum 
vas_cop_type cop_type,
 {
        int rc;
 
-       if (!copypaste_feat)
+       rc = pseries_vas_init();
+       if (rc || !copypaste_feat)
                return -ENOTSUPP;
 
        rc = vas_register_coproc_api(mod, cop_type, name, &vops_pseries);
@@ -531,7 +534,7 @@ static int get_vas_capabilities(u8 feat, enum 
vas_cop_feat_type type,
        return 0;
 }
 
-static int __init pseries_vas_init(void)
+static int pseries_vas_init(void)
 {
        struct hv_vas_cop_feat_caps *hv_cop_caps;
        struct hv_vas_all_caps *hv_caps;
@@ -592,4 +595,3 @@ static int __init pseries_vas_init(void)
        kfree(hv_caps);
        return rc;
 }
-machine_device_initcall(pseries, pseries_vas_init);