linux-kernel - Re: [PATCH V2 1/2] x86/tdx: Eliminate duplicate code in tdx_clear

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Message-ID: <cb995757-55cb-467b-bce9-31245eee0837@linux.intel.com>
Date: Fri, 4 Jul 2025 14:44:44 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>, pbonzini@...hat.com,
 seanjc@...gle.com, vannapurve@...gle.com, Tony Luck <tony.luck@...el.com>,
 Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, x86@...nel.org, H Peter Anvin
 <hpa@...or.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 rick.p.edgecombe@...el.com, kirill.shutemov@...ux.intel.com,
 kai.huang@...el.com, reinette.chatre@...el.com, xiaoyao.li@...el.com,
 tony.lindgren@...ux.intel.com, isaku.yamahata@...el.com,
 yan.y.zhao@...el.com, chao.gao@...el.com
Subject: Re: [PATCH V2 1/2] x86/tdx: Eliminate duplicate code in
 tdx_clear_page()



On 7/3/2025 11:37 PM, Adrian Hunter wrote:
> tdx_clear_page() and reset_tdx_pages() duplicate the TDX page clearing
> logic.  Rename reset_tdx_pages() to tdx_quirk_reset_paddr() and use it
> in place of tdx_clear_page().
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>

> ---
>
>
> Changes in V2:
>
> 	Rename reset_tdx_pages() to tdx_quirk_reset_paddr()
> 	Call tdx_quirk_reset_paddr() directly
>
>
>   arch/x86/include/asm/tdx.h  |  2 ++
>   arch/x86/kvm/vmx/tdx.c      | 25 +++----------------------
>   arch/x86/virt/vmx/tdx/tdx.c |  5 +++--
>   3 files changed, 8 insertions(+), 24 deletions(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 7ddef3a69866..f66328404724 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -131,6 +131,8 @@ int tdx_guest_keyid_alloc(void);
>   u32 tdx_get_nr_guest_keyids(void);
>   void tdx_guest_keyid_free(unsigned int keyid);
>   
> +void tdx_quirk_reset_paddr(unsigned long base, unsigned long size);
> +
>   struct tdx_td {
>   	/* TD root structure: */
>   	struct page *tdr_page;
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index a08e7055d1db..031e36665757 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -276,25 +276,6 @@ static inline void tdx_disassociate_vp(struct kvm_vcpu *vcpu)
>   	vcpu->cpu = -1;
>   }
>   
> -static void tdx_clear_page(struct page *page)
> -{
> -	const void *zero_page = (const void *) page_to_virt(ZERO_PAGE(0));
> -	void *dest = page_to_virt(page);
> -	unsigned long i;
> -
> -	/*
> -	 * The page could have been poisoned.  MOVDIR64B also clears
> -	 * the poison bit so the kernel can safely use the page again.
> -	 */
> -	for (i = 0; i < PAGE_SIZE; i += 64)
> -		movdir64b(dest + i, zero_page);
> -	/*
> -	 * MOVDIR64B store uses WC buffer.  Prevent following memory reads
> -	 * from seeing potentially poisoned cache.
> -	 */
> -	__mb();
> -}
> -
>   static void tdx_no_vcpus_enter_start(struct kvm *kvm)
>   {
>   	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> @@ -340,7 +321,7 @@ static int tdx_reclaim_page(struct page *page)
>   
>   	r = __tdx_reclaim_page(page);
>   	if (!r)
> -		tdx_clear_page(page);
> +		tdx_quirk_reset_paddr(page_to_phys(page), PAGE_SIZE);
>   	return r;
>   }
>   
> @@ -589,7 +570,7 @@ static void tdx_reclaim_td_control_pages(struct kvm *kvm)
>   		pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err);
>   		return;
>   	}
> -	tdx_clear_page(kvm_tdx->td.tdr_page);
> +	tdx_quirk_reset_paddr(page_to_phys(kvm_tdx->td.tdr_page), PAGE_SIZE);
>   
>   	__free_page(kvm_tdx->td.tdr_page);
>   	kvm_tdx->td.tdr_page = NULL;
> @@ -1689,7 +1670,7 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
>   		pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err);
>   		return -EIO;
>   	}
> -	tdx_clear_page(page);
> +	tdx_quirk_reset_paddr(page_to_phys(page), PAGE_SIZE);
>   	tdx_unpin(kvm, page);
>   	return 0;
>   }
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index c7a9a087ccaf..14d93ed05bd2 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -637,7 +637,7 @@ static int tdmrs_set_up_pamt_all(struct tdmr_info_list *tdmr_list,
>    * clear these pages.  Note this function doesn't flush cache of
>    * these TDX private pages.  The caller should make sure of that.
>    */
> -static void reset_tdx_pages(unsigned long base, unsigned long size)
> +void tdx_quirk_reset_paddr(unsigned long base, unsigned long size)
>   {
>   	const void *zero_page = (const void *)page_address(ZERO_PAGE(0));
>   	unsigned long phys, end;
> @@ -653,10 +653,11 @@ static void reset_tdx_pages(unsigned long base, unsigned long size)
>   	 */
>   	mb();
>   }
> +EXPORT_SYMBOL_GPL(tdx_quirk_reset_paddr);
>   
>   static void tdmr_reset_pamt(struct tdmr_info *tdmr)
>   {
> -	tdmr_do_pamt_func(tdmr, reset_tdx_pages);
> +	tdmr_do_pamt_func(tdmr, tdx_quirk_reset_paddr);
>   }
>   
>   static void tdmrs_reset_pamt_all(struct tdmr_info_list *tdmr_list)