linux-kernel - Re: [PATCH v19 033/130] KVM: TDX: Add helper function to read TDX metadata in array

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Date: Fri, 15 Mar 2024 11:27:56 +1300
From: "Huang, Kai" <kai.huang@...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>, <chen.bo@...el.com>, <hang.yuan@...el.com>,
	<tina.zhang@...el.com>
Subject: Re: [PATCH v19 033/130] KVM: TDX: Add helper function to read TDX
 metadata in array



On 26/02/2024 9:25 pm, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> To read meta data in series, use table.
> Instead of metadata_read(fid0, &data0); metadata_read(...); ...
> table = { {fid0, &data0}, ...}; metadata-read(tables).

This explains nothing why the code introduced in patch 5 cannot be used.

> TODO: Once the TDX host code introduces its framework to read TDX metadata,
> drop this patch and convert the code that uses this.

Seriously, what is this?? Please treat your patches as "official" patches.

> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
> v18:
> - newly added
> ---
>   arch/x86/kvm/vmx/tdx.c | 45 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 45 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index cde971122c1e..dce21f675155 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -6,6 +6,7 @@
>   #include "capabilities.h"
>   #include "x86_ops.h"
>   #include "x86.h"
> +#include "tdx_arch.h"
>   #include "tdx.h"
>   
>   #undef pr_fmt
> @@ -39,6 +40,50 @@ static void __used tdx_guest_keyid_free(int keyid)
>   	ida_free(&tdx_guest_keyid_pool, keyid);
>   }
>   
> +#define TDX_MD_MAP(_fid, _ptr)			\
> +	{ .fid = MD_FIELD_ID_##_fid,		\
> +	  .ptr = (_ptr), }
> +
> +struct tdx_md_map {
> +	u64 fid;
> +	void *ptr;
> +};
> +
> +static size_t tdx_md_element_size(u64 fid)
> +{
> +	switch (TDX_MD_ELEMENT_SIZE_CODE(fid)) {
> +	case TDX_MD_ELEMENT_SIZE_8BITS:
> +		return 1;
> +	case TDX_MD_ELEMENT_SIZE_16BITS:
> +		return 2;
> +	case TDX_MD_ELEMENT_SIZE_32BITS:
> +		return 4;
> +	case TDX_MD_ELEMENT_SIZE_64BITS:
> +		return 8;
> +	default:
> +		WARN_ON_ONCE(1);
> +		return 0;
> +	}
> +}
> +
> +static int __used tdx_md_read(struct tdx_md_map *maps, int nr_maps)
> +{
> +	struct tdx_md_map *m;
> +	int ret, i;
> +	u64 tmp;
> +
> +	for (i = 0; i < nr_maps; i++) {
> +		m = &maps[i];
> +		ret = tdx_sys_metadata_field_read(m->fid, &tmp);
> +		if (ret)
> +			return ret;
> +
> +		memcpy(m->ptr, &tmp, tdx_md_element_size(m->fid));
> +	}
> +
> +	return 0;
> +}
> +

It's just insane to have two duplicated mechanism for metadata reading.

This will only confuse people.

If there's anything missing in patch 1-5, we can enhance them.