[PATCH v10 2/2] x86/tdx: Support vmalloc() for tdx_enc_status_changed()

[Dexuan Cui <decui@xxxxxxxxxxxxx>]

When a TDX guest runs on Hyper-V, the hv_netvsc driver's netvsc_init_buf()
allocates buffers using vzalloc(), and needs to share the buffers with the
host OS by calling set_memory_decrypted(), which is not working for
vmalloc() yet. Add the support by handling the pages one by one.

Co-developed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
---
 arch/x86/coco/tdx/tdx.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

Changes in v10:
  Dave kindly improved tdx_enc_status_changed():
    Call tdx_enc_status_changed_phys() only once.
    Make the change concise and more readable
    See https://lwn.net/ml/linux-kernel/69b46bf3-40ab-c379-03d5-efd537ed44c7@xxxxxxxxx/

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 746075d20cd2d..38044bb32c498 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -7,6 +7,7 @@
 #include <linux/cpufeature.h>
 #include <linux/export.h>
 #include <linux/io.h>
+#include <linux/mm.h>
 #include <asm/coco.h>
 #include <asm/tdx.h>
 #include <asm/vmx.h>
@@ -753,6 +754,19 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
 	return false;
 }
 
+static bool tdx_enc_status_changed_phys(phys_addr_t start, phys_addr_t end,
+					bool enc)
+{
+	if (!tdx_map_gpa(start, end, enc))
+		return false;
+
+	/* shared->private conversion requires memory to be accepted before use */
+	if (enc)
+		return tdx_accept_memory(start, end);
+
+	return true;
+}
+
 /*
  * Inform the VMM of the guest's intent for this physical page: shared with
  * the VMM or private to the guest.  The VMM is expected to change its mapping
@@ -760,15 +774,25 @@ static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
  */
 static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 {
-	phys_addr_t start = __pa(vaddr);
-	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
+	unsigned long start = vaddr;
+	unsigned long end = start + numpages * PAGE_SIZE;
+	unsigned long step = end - start;
+	unsigned long addr;
 
-	if (!tdx_map_gpa(start, end, enc))
+	if (offset_in_page(start) != 0)
 		return false;
 
-	/* shared->private conversion requires memory to be accepted before use */
-	if (enc)
-		return tdx_accept_memory(start, end);
+	/* Step through page-by-page for vmalloc() mappings: */
+	if (is_vmalloc_addr((void *)vaddr))
+		step = PAGE_SIZE;
+
+	for (addr = start; addr < end; addr += step) {
+		phys_addr_t start_pa = slow_virt_to_phys((void *)addr);
+		phys_addr_t end_pa   = start_pa + step;
+
+		if (!tdx_enc_status_changed_phys(start_pa, end_pa, enc))
+			return false;
+	}
 
 	return true;
 }
-- 
2.25.1