linux-kernel - Re: [PATCH v6 04/16] KVM: TDX: Pass size to tdx_measure

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Date:   Thu, 16 Nov 2023 16:57:26 +0800
From:   Binbin Wu <binbin.wu@...ux.intel.com>
To:     isaku.yamahata@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        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,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH v6 04/16] KVM: TDX: Pass size to tdx_measure_page()



On 11/7/2023 11:00 PM, isaku.yamahata@...el.com wrote:
> From: Xiaoyao Li <xiaoyao.li@...el.com>
>
> Extend tdx_measure_page() to pass size info so that it can measure
> large page as well.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/kvm/vmx/tdx.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 2d5c86e06c5f..a728175c4a6d 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1434,13 +1434,15 @@ void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int pgd_level)
>   	td_vmcs_write64(to_tdx(vcpu), SHARED_EPT_POINTER, root_hpa & PAGE_MASK);
>   }
>   
> -static void tdx_measure_page(struct kvm_tdx *kvm_tdx, hpa_t gpa)
> +static void tdx_measure_page(struct kvm_tdx *kvm_tdx, hpa_t gpa, int size)
IMHO, it's better to pass kvm page level instead of size here to align with
other APIs.

>   {
>   	struct tdx_module_args out;
>   	u64 err;
>   	int i;
>   
> -	for (i = 0; i < PAGE_SIZE; i += TDX_EXTENDMR_CHUNKSIZE) {
> +	WARN_ON_ONCE(size % TDX_EXTENDMR_CHUNKSIZE);

If passed level instead of size, then no need to check KVM_HPAGE_SIZE(level)
against TDX_EXTENDMR_CHUNKSIZE

But same qeustion, tdx_measure_page() is only for tdh_mem_page_add(), is 
this
change necessary?

> +
> +	for (i = 0; i < size; i += TDX_EXTENDMR_CHUNKSIZE) {
>   		err = tdh_mr_extend(kvm_tdx->tdr_pa, gpa + i, &out);
>   		if (KVM_BUG_ON(err, &kvm_tdx->kvm)) {
>   			pr_tdx_error(TDH_MR_EXTEND, err, &out);
> @@ -1544,7 +1546,7 @@ static int tdx_sept_page_add(struct kvm *kvm, gfn_t gfn,
>   		tdx_unpin(kvm, pfn);
>   		return -EIO;
>   	} else if (measure)
> -		tdx_measure_page(kvm_tdx, gpa);
> +		tdx_measure_page(kvm_tdx, gpa, KVM_HPAGE_SIZE(level));
>   
>   	return 0;
>