linux-kernel - [PATCH] x86/tdx: Fix crash on kexec

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Date: Sat, 29 Jun 2024 16:06:20 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Michael Kelley <mikelley@...rosoft.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>
Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Dexuan Cui <decui@...rosoft.com>,
	linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86/tdx: Fix crash on kexec

The function tdx_enc_status_changed() was modified to handle vmalloc()
mappings. It now utilizes slow_virt_to_phys() to determine the physical
address of the page by walking page tables and looking for the physical
address in the page table entry.

However, this adjustment conflicted with the enabling of kexec. The
function tdx_kexec_finish() clears the page table entry before calling
tdx_enc_status_changed(), causing a BUG_ON() error in
slow_virt_to_phys().

To address this issue, tdx_enc_status_change() should use __pa() to
obtain physical addresses whenever possible. The virt_addr_valid() check
will handle such cases, while any other scenarios, including vmalloc()
mappings, will resort to slow_virt_to_phys().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Fixes: e1b8ac3aae58 ("x86/tdx: Support vmalloc() for tdx_enc_status_changed()")
---
 arch/x86/coco/tdx/tdx.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index ef8ec2425998..8f471260924f 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -813,8 +813,16 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
 		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;
+		phys_addr_t start_pa;
+		phys_addr_t end_pa;
+
+		/* The check fails on vmalloc() mappings */
+		if (virt_addr_valid(addr))
+			start_pa = __pa(addr);
+		else
+			start_pa = slow_virt_to_phys((void *)addr);
+
+		end_pa = start_pa + step;
 
 		if (!tdx_enc_status_changed_phys(start_pa, end_pa, enc))
 			return false;
-- 
2.43.0