Re: [PATCH 3/4] crypto/ccp: support setting RAPL_DIS in SNP_INIT_EX

[Tycho Andersen]

On Mon, Feb 23, 2026 at 08:40:19AM -0800, Sean Christopherson wrote:
> On Mon, Feb 23, 2026, Tycho Andersen wrote:
> > From: "Tycho Andersen (AMD)" 
> > 
> > The kernel allows setting the RAPL_DIS policy bit, but had no way to set
> 
> Please actually say what RAPL_DIS is and does, and explain why this is the
> correct approach.  I genuinely have no idea what the impact of this patch is,
> (beyond disabling something, obviously).

Sure, the easiest thing is probably to quote the firmware PDF:

Some processors support the Running Average Power Limit (RAPL)
feature which provides information about power utilization of
software. RAPL can be disabled using the RAPL_DIS flag in
SNP_INIT_EX to disable RAPL while SNP firmware is in the INIT
state. Guests may require that RAPL is disabled by using the
POLICY.RAPL_DIS guest policy flag.

I'll add this to the message in the next version.

I will also split out the RAPL_DIS stuff from the test fix for the
firmware update.

Tycho

Re: [PATCH 3/4] crypto/ccp: support setting RAPL_DIS in SNP_INIT_EX

[Sean Christopherson]

On Mon, Feb 23, 2026, Tycho Andersen wrote:
> From: "Tycho Andersen (AMD)" 
> 
> The kernel allows setting the RAPL_DIS policy bit, but had no way to set

Please actually say what RAPL_DIS is and does, and explain why this is the
correct approach.  I genuinely have no idea what the impact of this patch is,
(beyond disabling something, obviously).

> the RAPL_DIS bit during SNP_INIT_EX. Setting the policy bit would always
> result in:
> 
> [  898.840286] ccp :a9:00.5: sev command 0xa0 failed (0x0007)
> 
> Allow setting the RAPL_DIS bit during SNP_INIT_EX via a module parameter.
> If the hardware does not support RAPL_DIS, log and disable the module
> parameter.
> 
> Signed-off-by: Tycho Andersen (AMD) 
> ---
>  drivers/crypto/ccp/sev-dev.c | 14 ++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 096f993974d1..362126453ef0 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -75,6 +75,10 @@ static bool psp_init_on_probe = true;
>  module_param(psp_init_on_probe, bool, 0444);
>  MODULE_PARM_DESC(psp_init_on_probe, "  if true, the PSP will be initialized 
> on module init. Else the PSP will be initialized on the first command 
> requiring it");
>  
> +static bool rapl_disable;
> +module_param(rapl_disable, bool, 0444);
> +MODULE_PARM_DESC(rapl_disable, "  if true, the RAPL_DIS bit will be set 
> during INIT_EX if supported");
> +
>  #if IS_ENABLED(CONFIG_PCI_TSM)
>  static bool sev_tio_enabled = true;
>  module_param_named(tio, sev_tio_enabled, bool, 0444);
> @@ -1428,6 +1432,16 @@ static int __sev_snp_init_locked(int *error, unsigned 
> int max_snp_asid)
>   data.max_snp_asid = max_snp_asid;
>   }
>  
> + if (rapl_disable) {
> + if (sev->snp_feat_info_0.ecx & 
> SNP_RAPL_DISABLE_SUPPORTED) {
> + data.rapl_dis = 1;
> + } else {
> + dev_info(sev->dev,
> + "SEV: RAPL_DIS requested, but not 
> supported");
> + rapl_disable = false;
> + }
> + }
> +
>   data.init_rmp = 1;
>   data.list_paddr_en = 1;
>   data.list_paddr = __psp_pa(snp_range_list);
> -- 
> 2.53.0
>