After removing or reclaiming a guest private page or a control page from a TD, zero the physical page using movdir64b(), enabling the kernel to reuse the pages. Introduce the function tdx_clear_folio() to zero out physical memory using movdir64b(), starting from the page at "start_idx" within a "folio" and spanning "npages" contiguous PFNs. Convert tdx_clear_page() to be a helper function to facilitate the zeroing of 4KB pages. Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx> --- RFC v2: - Add tdx_clear_folio(). - Drop inner loop _tdx_clear_page() and move __mb() outside of the loop. (Rick) - Use C99-style definition of variables inside a for loop. - Note: [1] also changes tdx_clear_page(). RFC v2 is not based on [1] now. [1] https://lore.kernel.org/all/20250724130354.79392-2-adrian.hunter@xxxxxxxxx RFC v1: - split out, let tdx_clear_page() accept level. --- arch/x86/kvm/vmx/tdx.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 8eaf8431c5f1..4fabefb27135 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -277,18 +277,21 @@ static inline void tdx_disassociate_vp(struct kvm_vcpu *vcpu) vcpu->cpu = -1; } -static void tdx_clear_page(struct page *page) +static void tdx_clear_folio(struct folio *folio, unsigned long start_idx, + unsigned long npages) { 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); + for (unsigned long j = 0; j < npages; j++) { + void *dest = page_to_virt(folio_page(folio, start_idx + j)); + + for (unsigned long 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. @@ -296,6 +299,13 @@ static void tdx_clear_page(struct page *page) __mb(); } +static inline void tdx_clear_page(struct page *page) +{ + struct folio *folio = page_folio(page); + + tdx_clear_folio(folio, folio_page_idx(folio, page), 1); +} + static void tdx_no_vcpus_enter_start(struct kvm *kvm) { struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm); @@ -1736,7 +1746,7 @@ 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_clear_folio(folio, folio_page_idx(folio, page), KVM_PAGES_PER_HPAGE(level)); tdx_pamt_put(page, level); tdx_unpin(kvm, page); return 0; -- 2.43.2
