linux-kernel - Re: [RFC PATCH 07/21] KVM: TDX: Add a helper for WBINVD on huge pages with TD's keyID

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Message-ID: <a3858c57-5de0-45ae-ab33-30e4c233337d@linux.intel.com>
Date: Tue, 6 May 2025 16:37:22 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org, x86@...nel.org, rick.p.edgecombe@...el.com,
 dave.hansen@...el.com, kirill.shutemov@...el.com, tabba@...gle.com,
 ackerleytng@...gle.com, quic_eberman@...cinc.com, michael.roth@....com,
 david@...hat.com, vannapurve@...gle.com, vbabka@...e.cz, jroedel@...e.de,
 thomas.lendacky@....com, pgonda@...gle.com, zhiquan1.li@...el.com,
 fan.du@...el.com, jun.miao@...el.com, ira.weiny@...el.com,
 isaku.yamahata@...el.com, xiaoyao.li@...el.com, chao.p.peng@...el.com
Subject: Re: [RFC PATCH 07/21] KVM: TDX: Add a helper for WBINVD on huge pages
 with TD's keyID



On 4/24/2025 11:05 AM, Yan Zhao wrote:
> From: Xiaoyao Li <xiaoyao.li@...el.com>
>
> After a guest page is removed from the S-EPT, KVM calls
> tdh_phymem_page_wbinvd_hkid() to execute WBINVD on the page using the TD's
> keyID.
>
> Add a helper function that takes level information to perform WBINVD on a
> huge page.
>
> [Yan: split patch, added a helper, rebased to use struct page]
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
> ---
>   arch/x86/kvm/vmx/tdx.c | 24 +++++++++++++++++++-----
>   1 file changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 69f3140928b5..355b21fc169f 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1586,6 +1586,23 @@ int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
>   	return tdx_mem_page_record_premap_cnt(kvm, level);
>   }
>   
> +static inline u64 tdx_wbinvd_page(struct kvm *kvm, u64 hkid, struct page *page, int level)
> +{
> +	unsigned long nr = KVM_PAGES_PER_HPAGE(level);
> +	unsigned long idx = 0;
> +	u64 err;
> +
> +	while (nr--) {
> +		err = tdh_phymem_page_wbinvd_hkid(hkid, nth_page(page, idx++));
> +
> +		if (KVM_BUG_ON(err, kvm)) {
> +			pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err);
> +			return err;
> +		}
> +	}
> +	return err;
> +}
> +
>   static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
>   				      enum pg_level level, struct page *page)
>   {
> @@ -1625,12 +1642,9 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
>   		return -EIO;
>   	}
>   
> -	err = tdh_phymem_page_wbinvd_hkid((u16)kvm_tdx->hkid, page);
> -
> -	if (KVM_BUG_ON(err, kvm)) {
> -		pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err);
> +	err = tdx_wbinvd_page(kvm, kvm_tdx->hkid, page, level);
> +	if (err)

It can add unlikely() here.
Also the err is not used after check, maybe it can be combined as:

if (unlikely(tdx_wbinvd_page(kvm, kvm_tdx->hkid, page, level)))
         return -EIO;


>   		return -EIO;
> -	}
>   
>   	tdx_clear_page(page, level);
>   	tdx_unpin(kvm, page);