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

Tony Lindgren
2024-08-30T07:21:32Z

On Thu, Aug 15, 2024 at 03:59:26PM +0800, Xu Yilun wrote:
> > --- 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?

It's needed for kvm_gfn_direct_bits(), but should have been added in a
later patch.

> > +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.

Hmm do we want to add also positive numbers for errors for this function?

> > + 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.

Looks like these both already changed in a later patch
"KVM: TDX: Report kvm_tdx_caps in KVM_TDX_CAPABILITIES".

Regards,

Tony