linux-kernel - Re: [PATCH v15 018/115] KVM: TDX: x86: Add ioctl to get TDX systemwide parameters

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Date:   Tue, 15 Aug 2023 15:56:58 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        hang.yuan@...el.com, tina.zhang@...el.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v15 018/115] KVM: TDX: x86: Add ioctl to get TDX
 systemwide parameters

On 7/26/2023 6:13 AM, isaku.yamahata@...el.com wrote:
...
> +static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
> +{
> +	struct kvm_tdx_capabilities __user *user_caps;
> +	const struct tdsysinfo_struct *tdsysinfo;
> +	struct kvm_tdx_capabilities *caps = NULL;
> +	int ret;

needs to initialize ret to 0; otherwise it returns random value on success.

> +
> +	BUILD_BUG_ON(sizeof(struct kvm_tdx_cpuid_config) !=
> +		     sizeof(struct tdx_cpuid_config));
> +
> +	if (cmd->flags)
> +		return -EINVAL;
> +
> +	tdsysinfo = tdx_get_sysinfo();
> +	if (!tdsysinfo)
> +		return -EOPNOTSUPP;
> +
> +	caps = kmalloc(sizeof(*caps), GFP_KERNEL);
> +	if (!caps)
> +		return -ENOMEM;
> +
> +	user_caps = (void __user *)cmd->data;
> +	if (copy_from_user(caps, user_caps, sizeof(*caps))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (caps->nr_cpuid_configs < tdsysinfo->num_cpuid_config) {
> +		ret = -E2BIG;
> +		goto out;
> +	}
> +
> +	*caps = (struct kvm_tdx_capabilities) {
> +		.attrs_fixed0 = tdsysinfo->attributes_fixed0,
> +		.attrs_fixed1 = tdsysinfo->attributes_fixed1,
> +		.xfam_fixed0 = tdsysinfo->xfam_fixed0,
> +		.xfam_fixed1 = tdsysinfo->xfam_fixed1,
> +		.supported_gpaw = TDX_CAP_GPAW_48 |
> +		(kvm_get_shadow_phys_bits() >= 52 &&
> +		 cpu_has_vmx_ept_5levels()) ? TDX_CAP_GPAW_52 : 0,
> +		.nr_cpuid_configs = tdsysinfo->num_cpuid_config,
> +		.padding = 0,
> +	};
> +
> +	if (copy_to_user(user_caps, caps, sizeof(*caps))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +	if (copy_to_user(user_caps->cpuid_configs, &tdsysinfo->cpuid_configs,
> +			 tdsysinfo->num_cpuid_config *
> +			 sizeof(struct tdx_cpuid_config))) {
> +		ret = -EFAULT;
> +	}
> +
> +out:
> +	/* kfree() accepts NULL. */
> +	kfree(caps);
> +	return ret;
> +}