6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kirill A. Shutemov kirill.shutemov@linux.intel.com
[ Upstream commit c3abbf1376874f0d6eb22859a8655831644efa42 ]
The kernel will convert all shared memory back to private during kexec. The direct mapping page tables will provide information on which memory is shared.
It is extremely important to convert all shared memory. If a page is missed, it will cause the second kernel to crash when it accesses it.
Keep track of the number of shared pages. This will allow for cross-checking against the shared information in the direct mapping and reporting if the shared bit is lost.
Memory conversion is slow and does not happen often. Global atomic is not going to be a bottleneck.
Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Reviewed-by: Kai Huang kai.huang@intel.com Tested-by: Tao Liu ltao@redhat.com Link: https://lore.kernel.org/r/20240614095904.1345461-10-kirill.shutemov@linux.in... Stable-dep-of: d4fc4d014715 ("x86/tdx: Fix "in-kernel MMIO" check") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/coco/tdx/tdx.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index fdcc081317764..729ef77b65865 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -38,6 +38,8 @@
#define TDREPORT_SUBTYPE_0 0
+static atomic_long_t nr_shared; + /* Called from __tdx_hypercall() for unrecoverable failure */ noinstr void __noreturn __tdx_hypercall_failed(void) { @@ -820,6 +822,11 @@ static int tdx_enc_status_change_finish(unsigned long vaddr, int numpages, if (!enc && !tdx_enc_status_changed(vaddr, numpages, enc)) return -EIO;
+ if (enc) + atomic_long_sub(numpages, &nr_shared); + else + atomic_long_add(numpages, &nr_shared); + return 0; }