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().
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@kernel.org>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
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 | 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 573d6f7d1694..1b549de6da06 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_paddr(page_to_phys(page), PAGE_SIZE);
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_paddr(page_to_phys(kvm_tdx->td.tdr_page), PAGE_SIZE);
__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_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)
--
2.48.1On Tue, Jul 22, 2025, Adrian Hunter wrote:
> 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 573d6f7d1694..1b549de6da06 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_paddr(page_to_phys(page), PAGE_SIZE);
This is silly. Literally every use in KVM is on a struct page. I agree with
Dave that having a wrapper with a completely unrelated name is confusing, but
that's a naming problem, not a code problem.
And FWIW, I find tdx_quirk_reset_paddr() confusing, because it reads like it's
resetting the address itself. But if KVM only ever uses tdx_quirk_reset_page(),
I don't care what you call the inner helper.
On 22/07/2025 17:11, Sean Christopherson wrote:
> On Tue, Jul 22, 2025, Adrian Hunter wrote:
>> 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 573d6f7d1694..1b549de6da06 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_paddr(page_to_phys(page), PAGE_SIZE);
>
> This is silly. Literally every use in KVM is on a struct page. I agree with
> Dave that having a wrapper with a completely unrelated name is confusing, but
> that's a naming problem, not a code problem.
>
> And FWIW, I find tdx_quirk_reset_paddr() confusing, because it reads like it's
> resetting the address itself. But if KVM only ever uses tdx_quirk_reset_page(),
> I don't care what you call the inner helper.
As you say, Dave's second option was:
"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)"
So I will do that for V4 unless there are further comments.
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