Re: [PATCH v5 09/10] KVM: SVM: Use new ccp GCTX API

[Tom Lendacky <thomas.lendacky@amd.com>]

On 11/7/24 17:24, Dionna Glaze wrote:
> Guest context pages should be near 1-to-1 with allocated ASIDs. With the
> GCTX API, the ccp driver is better able to associate guest context pages
> with the ASID that is/will be bound to it.
> 
> This is important to the firmware hotloading implementation to not
> corrupt any running VM's guest context page before userspace commits a
> new firmware.
> 
> CC: Sean Christopherson <seanjc@google.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: Dave Hansen <dave.hansen@linux.intel.com>
> CC: Ashish Kalra <ashish.kalra@amd.com>
> CC: Tom Lendacky <thomas.lendacky@amd.com>
> CC: John Allen <john.allen@amd.com>
> CC: Herbert Xu <herbert@gondor.apana.org.au>
> CC: "David S. Miller" <davem@davemloft.net>
> CC: Michael Roth <michael.roth@amd.com>
> CC: Luis Chamberlain <mcgrof@kernel.org>
> CC: Russ Weight <russ.weight@linux.dev>
> CC: Danilo Krummrich <dakr@redhat.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: "Rafael J. Wysocki" <rafael@kernel.org>
> CC: Tianfei zhang <tianfei.zhang@intel.com>
> CC: Alexey Kardashevskiy <aik@amd.com>
> 
> Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
> ---
>  arch/x86/kvm/svm/sev.c | 74 ++++++++++++------------------------------
>  1 file changed, 20 insertions(+), 54 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index cea41b8cdabe4..d7cef84750b33 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -89,7 +89,7 @@ static unsigned int nr_asids;
>  static unsigned long *sev_asid_bitmap;
>  static unsigned long *sev_reclaim_asid_bitmap;
>  
> -static int snp_decommission_context(struct kvm *kvm);
> +static int kvm_decommission_snp_context(struct kvm *kvm);

Why the name change? It seems like it just makes the patch a bit harder
to follow since there are two things going on.

Thanks,
Tom

>  
>  struct enc_region {
>  	struct list_head list;
> @@ -2168,51 +2168,12 @@ int sev_dev_get_attr(u32 group, u64 attr, u64 *val)
>  	}
>  }
>  
> -/*
> - * The guest context contains all the information, keys and metadata
> - * associated with the guest that the firmware tracks to implement SEV
> - * and SNP features. The firmware stores the guest context in hypervisor
> - * provide page via the SNP_GCTX_CREATE command.
> - */
> -static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)
> -{
> -	struct sev_data_snp_addr data = {};
> -	void *context;
> -	int rc;
> -
> -	/* Allocate memory for context page */
> -	context = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
> -	if (!context)
> -		return ERR_PTR(-ENOMEM);
> -
> -	data.address = __psp_pa(context);
> -	rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_GCTX_CREATE, &data, &argp->error);
> -	if (rc) {
> -		pr_warn("Failed to create SEV-SNP context, rc %d fw_error %d",
> -			rc, argp->error);
> -		snp_free_firmware_page(context);
> -		return ERR_PTR(rc);
> -	}
> -
> -	return context;
> -}
> -
> -static int snp_bind_asid(struct kvm *kvm, int *error)
> -{
> -	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> -	struct sev_data_snp_activate data = {0};
> -
> -	data.gctx_paddr = __psp_pa(sev->snp_context);
> -	data.asid = sev_get_asid(kvm);
> -	return sev_issue_cmd(kvm, SEV_CMD_SNP_ACTIVATE, &data, error);
> -}
> -
>  static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  {
>  	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>  	struct sev_data_snp_launch_start start = {0};
>  	struct kvm_sev_snp_launch_start params;
> -	int rc;
> +	int rc, asid;
>  
>  	if (!sev_snp_guest(kvm))
>  		return -ENOTTY;
> @@ -2238,14 +2199,19 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	if (params.policy & SNP_POLICY_MASK_SINGLE_SOCKET)
>  		return -EINVAL;
>  
> -	sev->snp_context = snp_context_create(kvm, argp);
> +	rc = sev_check_external_user(argp->sev_fd);
> +	if (rc)
> +		return rc;
> +
> +	asid = sev_get_asid(kvm);
> +	sev->snp_context = sev_snp_create_context(asid, &argp->error);
>  	if (IS_ERR(sev->snp_context))
>  		return PTR_ERR(sev->snp_context);
>  
>  	start.gctx_paddr = __psp_pa(sev->snp_context);
>  	start.policy = params.policy;
>  	memcpy(start.gosvw, params.gosvw, sizeof(params.gosvw));
> -	rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_START, &start, &argp->error);
> +	rc = sev_do_cmd(SEV_CMD_SNP_LAUNCH_START, &start, &argp->error);
>  	if (rc) {
>  		pr_debug("%s: SEV_CMD_SNP_LAUNCH_START firmware command failed, rc %d\n",
>  			 __func__, rc);
> @@ -2253,7 +2219,7 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	}
>  
>  	sev->fd = argp->sev_fd;
> -	rc = snp_bind_asid(kvm, &argp->error);
> +	rc = sev_snp_activate_asid(asid, &argp->error);
>  	if (rc) {
>  		pr_debug("%s: Failed to bind ASID to SEV-SNP context, rc %d\n",
>  			 __func__, rc);
> @@ -2263,7 +2229,7 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	return 0;
>  
>  e_free_context:
> -	snp_decommission_context(kvm);
> +	kvm_decommission_snp_context(kvm);
>  
>  	return rc;
>  }
> @@ -2874,26 +2840,26 @@ int sev_vm_copy_enc_context_from(struct kvm *kvm, unsigned int source_fd)
>  	return ret;
>  }
>  
> -static int snp_decommission_context(struct kvm *kvm)
> +static int kvm_decommission_snp_context(struct kvm *kvm)
>  {
>  	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> -	struct sev_data_snp_addr data = {};
> -	int ret;
> +	int ret, error;
>  
>  	/* If context is not created then do nothing */
>  	if (!sev->snp_context)
>  		return 0;
>  
> -	/* Do the decommision, which will unbind the ASID from the SNP context */
> -	data.address = __sme_pa(sev->snp_context);
> +	/*
> +	 * Do the decommision, which will unbind the ASID from the SNP context
> +	 * and free the context page.
> +	 */
>  	down_write(&sev_deactivate_lock);
> -	ret = sev_do_cmd(SEV_CMD_SNP_DECOMMISSION, &data, NULL);
> +	ret = sev_snp_guest_decommission(sev->asid, &error);
>  	up_write(&sev_deactivate_lock);
>  
> -	if (WARN_ONCE(ret, "Failed to release guest context, ret %d", ret))
> +	if (WARN_ONCE(ret, "Failed to release guest context, ret %d fw err %d", ret, error))
>  		return ret;
>  
> -	snp_free_firmware_page(sev->snp_context);
>  	sev->snp_context = NULL;
>  
>  	return 0;
> @@ -2947,7 +2913,7 @@ void sev_vm_destroy(struct kvm *kvm)
>  		 * Decomission handles unbinding of the ASID. If it fails for
>  		 * some unexpected reason, just leak the ASID.
>  		 */
> -		if (snp_decommission_context(kvm))
> +		if (kvm_decommission_snp_context(kvm))
>  			return;
>  	} else {
>  		sev_unbind_asid(kvm, sev->handle);