linux-kernel - Re: [PATCH] crypto: ccp - Dump SEV command buffer registers on SEV command error

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Date:   Wed, 11 Oct 2023 10:50:10 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     John Allen <john.allen@....com>, linux-crypto@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, thomas.lendacky@....com,
        herbert@...dor.apana.org.au
Subject: Re: [PATCH] crypto: ccp - Dump SEV command buffer registers on SEV
 command error

On 10/10/2023 15:44, John Allen wrote:
> PSP firmware may report additional error information in the SEV command
> buffer registers in situations where an error occurs as the result of an
> SEV command.  In this case, check if the command buffer registers have been
> modified and if so, dump the contents.
> 
> Signed-off-by: John Allen <john.allen@....com>

Reviewed-by: Mario Limonciello <mario.limonciello@....com>

> ---
>   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 f97166fba9d9..fcaccd0b5a65 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -309,6 +309,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   {
>   	struct psp_device *psp = psp_master;
>   	struct sev_device *sev;
> +	unsigned int cmdbuff_hi, cmdbuff_lo;
>   	unsigned int phys_lsb, phys_msb;
>   	unsigned int reg, ret = 0;
>   	int buf_len;
> @@ -371,6 +372,19 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   	if (FIELD_GET(PSP_CMDRESP_STS, reg)) {
>   		dev_dbg(sev->dev, "sev command %#x failed (%#010lx)\n",
>   			cmd, FIELD_GET(PSP_CMDRESP_STS, reg));
> +
> +		/*
> +		 * PSP firmware may report additional error information in the
> +		 * command buffer registers on error. Print contents of command
> +		 * buffer registers if they changed.
> +		 */
> +		cmdbuff_hi = ioread32(sev->io_regs + sev->vdata->cmdbuff_addr_hi_reg);
> +		cmdbuff_lo = ioread32(sev->io_regs + sev->vdata->cmdbuff_addr_lo_reg);
> +		if (cmdbuff_hi != phys_msb || cmdbuff_lo != phys_lsb) {
> +			dev_dbg(sev->dev, "Additional error information reported in cmdbuff:");
> +			dev_dbg(sev->dev, "  cmdbuff hi: %#010x\n", cmdbuff_hi);
> +			dev_dbg(sev->dev, "  cmdbuff lo: %#010x\n", cmdbuff_lo);
> +		}
>   		ret = -EIO;
>   	} else {
>   		ret = sev_write_init_ex_file_if_required(cmd);