linux-kernel - Re: [PATCH 09/25] KVM: TDX: Get system-wide info about TDX module on initialization

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Message-ID: <Zr21XioOyi0CZ+FV@yilunxu-OptiPlex-7050>
Date: Thu, 15 Aug 2024 15:59:26 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org,
	kai.huang@...el.com, isaku.yamahata@...il.com,
	tony.lindgren@...ux.intel.com, xiaoyao.li@...el.com,
	linux-kernel@...r.kernel.org,
	Isaku Yamahata <isaku.yamahata@...el.com>,
	Binbin Wu <binbin.wu@...ux.intel.com>
Subject: Re: [PATCH 09/25] KVM: TDX: Get system-wide info about TDX module on
 initialization

> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index de14e80d8f3a..90b44ebaf864 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -3,6 +3,7 @@
>  #include <asm/tdx.h>
>  #include "capabilities.h"
>  #include "x86_ops.h"
> +#include "mmu.h"

Is the header file still needed?

>  #include "tdx.h"
>  
>  #undef pr_fmt
> @@ -30,6 +31,72 @@ static void __used tdx_guest_keyid_free(int keyid)
>  	ida_free(&tdx_guest_keyid_pool, keyid);
>  }
>  
> +static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
> +{
> +	const struct tdx_sysinfo_td_conf *td_conf = &tdx_sysinfo->td_conf;
> +	struct kvm_tdx_capabilities __user *user_caps;
> +	struct kvm_tdx_capabilities *caps = NULL;
> +	int i, ret = 0;
> +
> +	/* flags is reserved for future use */
> +	if (cmd->flags)
> +		return -EINVAL;
> +
> +	caps = kmalloc(sizeof(*caps), GFP_KERNEL);
> +	if (!caps)
> +		return -ENOMEM;
> +
> +	user_caps = u64_to_user_ptr(cmd->data);
> +	if (copy_from_user(caps, user_caps, sizeof(*caps))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (caps->nr_cpuid_configs < td_conf->num_cpuid_config) {
> +		ret = -E2BIG;

How about output the correct num_cpuid_config to userspace as a hint,
to avoid user blindly retries.

> +		goto out;
> +	}
> +
> +	*caps = (struct kvm_tdx_capabilities) {
> +		.attrs_fixed0 = td_conf->attributes_fixed0,
> +		.attrs_fixed1 = td_conf->attributes_fixed1,
> +		.xfam_fixed0 = td_conf->xfam_fixed0,
> +		.xfam_fixed1 = td_conf->xfam_fixed1,
> +		.supported_gpaw = TDX_CAP_GPAW_48 |
> +		((kvm_host.maxphyaddr >= 52 &&
> +		  cpu_has_vmx_ept_5levels()) ? TDX_CAP_GPAW_52 : 0),
> +		.nr_cpuid_configs = td_conf->num_cpuid_config,
> +		.padding = 0,
> +	};
> +
> +	if (copy_to_user(user_caps, caps, sizeof(*caps))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	for (i = 0; i < td_conf->num_cpuid_config; i++) {
> +		struct kvm_tdx_cpuid_config cpuid_config = {
> +			.leaf = (u32)td_conf->cpuid_config_leaves[i],
> +			.sub_leaf = td_conf->cpuid_config_leaves[i] >> 32,
> +			.eax = (u32)td_conf->cpuid_config_values[i].eax_ebx,
> +			.ebx = td_conf->cpuid_config_values[i].eax_ebx >> 32,
> +			.ecx = (u32)td_conf->cpuid_config_values[i].ecx_edx,
> +			.edx = td_conf->cpuid_config_values[i].ecx_edx >> 32,
> +		};
> +
> +		if (copy_to_user(&(user_caps->cpuid_configs[i]), &cpuid_config,
                                  ^                           ^

I think the brackets could be removed.

> +					sizeof(struct kvm_tdx_cpuid_config))) {

sizeof(cpuid_config) could be better.

Thanks,
Yilun