tdx_clear_page() and reset_tdx_pages() duplicate the TDX page clearing
logic.  Keep the tdx_clear_page() prototype but call reset_tdx_pages() for
the implementation.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 arch/x86/include/asm/tdx.h  |  2 ++
 arch/x86/kvm/vmx/tdx.c      | 19 -------------------
 arch/x86/virt/vmx/tdx/tdx.c |  6 ++++++
 3 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 7ddef3a69866..e94eb0711bf1 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_clear_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 a08e7055d1db..098e4ee574bb 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);
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index c7a9a087ccaf..17a7a599facd 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -654,6 +654,12 @@ static void reset_tdx_pages(unsigned long base, unsigned long size)
 	mb();
 }
 
+void tdx_clear_page(struct page *page)
+{
+	reset_tdx_pages(page_to_phys(page), PAGE_SIZE);
+}
+EXPORT_SYMBOL_GPL(tdx_clear_page);
+
 static void tdmr_reset_pamt(struct tdmr_info *tdmr)
 {
 	tdmr_do_pamt_func(tdmr, reset_tdx_pages);
-- 
2.48.1

On 7/3/25 04:40, Adrian Hunter wrote:
> tdx_clear_page() and reset_tdx_pages() duplicate the TDX page clearing
> logic.  Keep the tdx_clear_page() prototype but call reset_tdx_pages() for
> the implementation.

Why keep the old prototype?

On 03/07/2025 17:14, Dave Hansen wrote:
> On 7/3/25 04:40, Adrian Hunter wrote:
>> tdx_clear_page() and reset_tdx_pages() duplicate the TDX page clearing
>> logic.  Keep the tdx_clear_page() prototype but call reset_tdx_pages() for
>> the implementation.
> 
> Why keep the old prototype?

What prototype would you prefer?

On 7/3/25 07:39, Adrian Hunter wrote:
> On 03/07/2025 17:14, Dave Hansen wrote:
>> On 7/3/25 04:40, Adrian Hunter wrote:
>>> tdx_clear_page() and reset_tdx_pages() duplicate the TDX page clearing
>>> logic.  Keep the tdx_clear_page() prototype but call reset_tdx_pages() for
>>> the implementation.
>> Why keep the old prototype?
> What prototype would you prefer?

My first reaction is that there should be _one_ function that does the
erratum-related clearing. I'd rather have the KVM sites use the slightly
cumbersome paddr/size arguments than have two functions.

Worst, case, have two functions that have similar names to make it clear
that they are doing the same thing.

It is *NOT* clear that:

	tdx_clear_page()
and
	reset_tdx_pages()

are doing the exact same thing.

I think I'd probably rename reset_tdx_pages() to tdx_reset_paddr() and
then use it in KVM like this:

	tdx_quirk_reset_paddr(page_to_phys(page), PAGE_SIZE);

The alternative would be to retain a function that keeps the 'struct
page' as an argument. Something like:

	tdx_quirk_reset_paddr(unsigned long base, unsigned long size)
and
	tdx_quirk_reset_page(struct page *page)

But the way proposed in this patch is very much a half measure.