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Date:   Tue, 2 Aug 2022 15:39:54 +0300
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Ashish Kalra <Ashish.Kalra@amd.com>
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Subject: Re: [PATCH Part2 v6 18/49] crypto: ccp: Provide APIs to query
 extended attestation report
Message-ID: <YukbGl5aZMK1PWRF@kernel.org>
References: <cover.1655761627.git.ashish.kalra@amd.com>
 <afae5980fd4adf52932a9d639a0b0bfe83255c0a.1655761627.git.ashish.kalra@amd.com>
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Precedence: bulk

I'd rephrase "Provide in-kernel API..." (e.g. not uapi).

On Mon, Jun 20, 2022 at 11:06:06PM +0000, Ashish Kalra wrote:
> From: Brijesh Singh <brijesh.singh@amd.com>
> 
> Version 2 of the GHCB specification defines VMGEXIT that is used to get
> the extended attestation report. The extended attestation report includes
> the certificate blobs provided through the SNP_SET_EXT_CONFIG.
> 
> The snp_guest_ext_guest_request() will be used by the hypervisor to get
> the extended attestation report. See the GHCB specification for more
> details.

What is "the hypersivor"? Could it be replaced with e.g. KVM for
clarity?

> 
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 43 ++++++++++++++++++++++++++++++++++++
>  include/linux/psp-sev.h      | 24 ++++++++++++++++++++
>  2 files changed, 67 insertions(+)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 97b479d5aa86..f6306b820b86 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -25,6 +25,7 @@
>  #include <linux/fs.h>
>  
>  #include <asm/smp.h>
> +#include <asm/sev.h>
>  
>  #include "psp-dev.h"
>  #include "sev-dev.h"
> @@ -1857,6 +1858,48 @@ int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
>  }
>  EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt);
>  
> +int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
> +				unsigned long vaddr, unsigned long *npages, unsigned long *fw_err)
> +{
> +	unsigned long expected_npages;
> +	struct sev_device *sev;
> +	int rc;
> +
> +	if (!psp_master || !psp_master->sev_data)
> +		return -ENODEV;
> +
> +	sev = psp_master->sev_data;
> +
> +	if (!sev->snp_inited)
> +		return -EINVAL;
> +
> +	/*
> +	 * Check if there is enough space to copy the certificate chain. Otherwise
> +	 * return ERROR code defined in the GHCB specification.
> +	 */
> +	expected_npages = sev->snp_certs_len >> PAGE_SHIFT;
> +	if (*npages < expected_npages) {
> +		*npages = expected_npages;
> +		*fw_err = SNP_GUEST_REQ_INVALID_LEN;
> +		return -EINVAL;
> +	}
> +
> +	rc = sev_do_cmd(SEV_CMD_SNP_GUEST_REQUEST, data, (int *)&fw_err);
> +	if (rc)
> +		return rc;
> +
> +	/* Copy the certificate blob */
> +	if (sev->snp_certs_data) {
> +		*npages = expected_npages;
> +		memcpy((void *)vaddr, sev->snp_certs_data, *npages << PAGE_SHIFT);
> +	} else {
> +		*npages = 0;
> +	}
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(snp_guest_ext_guest_request);

Undocumented export.

> +
>  static void sev_exit(struct kref *ref)
>  {
>  	misc_deregister(&misc_dev->misc);
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index a3bb792bb842..cd37ccd1fa1f 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -945,6 +945,23 @@ void *psp_copy_user_blob(u64 uaddr, u32 len);
>  void *snp_alloc_firmware_page(gfp_t mask);
>  void snp_free_firmware_page(void *addr);
>  
> +/**
> + * snp_guest_ext_guest_request - perform the SNP extended guest request command
> + *  defined in the GHCB specification.
> + *
> + * @data: the input guest request structure
> + * @vaddr: address where the certificate blob need to be copied.
> + * @npages: number of pages for the certificate blob.
> + *    If the specified page count is less than the certificate blob size, then the
> + *    required page count is returned with error code defined in the GHCB spec.
> + *    If the specified page count is more than the certificate blob size, then
> + *    page count is updated to reflect the amount of valid data copied in the
> + *    vaddr.
> + */

This kdoc is misplaced: it should be in sev-dev.c, right before the
implementation. Also it does not say anything about return value, and
still the return type is "int".

> +int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
> +				unsigned long vaddr, unsigned long *npages,
> +				unsigned long *error);
> +
>  #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
>  
>  static inline int
> @@ -992,6 +1009,13 @@ static inline void *snp_alloc_firmware_page(gfp_t mask)
>  
>  static inline void snp_free_firmware_page(void *addr) { }
>  
> +static inline int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
> +					      unsigned long vaddr, unsigned long *n,
> +					      unsigned long *error)
> +{
> +	return -ENODEV;
> +}
> +
>  #endif	/* CONFIG_CRYPTO_DEV_SP_PSP */
>  
>  #endif	/* __PSP_SEV_H__ */
> -- 
> 2.25.1
> 

BR, Jarkko