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Message-ID: <11f1346e-4a23-423d-978a-69e405e76d50@intel.com>
Date: Thu, 24 Jul 2025 15:52:14 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Dave Hansen <dave.hansen@...ux.intel.com>, <pbonzini@...hat.com>,
<seanjc@...gle.com>, <vannapurve@...gle.com>
CC: 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>, <kas@...nel.org>, <kai.huang@...el.com>,
<reinette.chatre@...el.com>, <xiaoyao.li@...el.com>,
<tony.lindgren@...ux.intel.com>, <binbin.wu@...ux.intel.com>,
<isaku.yamahata@...el.com>, <yan.y.zhao@...el.com>, <chao.gao@...el.com>
Subject: Re: [PATCH V5 1/3] x86/tdx: Eliminate duplicate code in
tdx_clear_page()
On 24/07/2025 15:48, 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 create
> tdx_quirk_reset_page() to call tdx_quirk_reset_paddr() and be used in
> place of tdx_clear_page().
>
> The new name reflects that, in fact, the clearing is necessary only for
> hardware with a certain quirk. That is dealt with in a subsequent patch
> but doing the rename here avoids additional churn.
>
> Note reset_tdx_pages() is slightly different from tdx_clear_page() because,
> more appropriately, it uses mb() in place of __mb(). Except when extra
> debugging is enabled (kcsan at present), mb() just calls __mb().
>
> Reviewed-by: Kirill A. Shutemov <kas@...nel.org>
> Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>
> Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Acked-by: Kai Huang <kai.huang@...el.com>
Forgot to add Sean's Ack from V4
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>
>
> Changes in V5:
>
> None
>
> Changes in V4:
>
> Add and use tdx_quirk_reset_page() for KVM (Sean)
>
> Changes in V3:
>
> Explain "quirk" rename in commit message (Rick)
> Explain mb() change in commit message (Rick)
> Add Rev'd-by, Ack'd-by tags
>
> 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 | 10 ++++++++--
> 3 files changed, 13 insertions(+), 24 deletions(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 7ddef3a69866..57b46f05ff97 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_page(struct page *page);
> +
> 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 573d6f7d1694..ebb36229c7c8 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -283,25 +283,6 @@ 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);
> @@ -347,7 +328,7 @@ static int tdx_reclaim_page(struct page *page)
>
> r = __tdx_reclaim_page(page);
> if (!r)
> - tdx_clear_page(page);
> + tdx_quirk_reset_page(page);
> return r;
> }
>
> @@ -596,7 +577,7 @@ 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_page(kvm_tdx->td.tdr_page);
>
> __free_page(kvm_tdx->td.tdr_page);
> kvm_tdx->td.tdr_page = NULL;
> @@ -1717,7 +1698,7 @@ 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_page(page);
> 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..fc8d8e444f15 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)
> +static 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;
> @@ -654,9 +654,15 @@ static void reset_tdx_pages(unsigned long base, unsigned long size)
> mb();
> }
>
> +void tdx_quirk_reset_page(struct page *page)
> +{
> + tdx_quirk_reset_paddr(page_to_phys(page), PAGE_SIZE);
> +}
> +EXPORT_SYMBOL_GPL(tdx_quirk_reset_page);
> +
> 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)
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