From 65fab5bc033aad1a9faf976caec46558c2f88319 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Wed, 6 Apr 2022 02:29:14 +0300 Subject: x86/tdx: Exclude shared bit from __PHYSICAL_MASK In TDX guests, by default memory is protected from host access. If a guest needs to communicate with the VMM (like the I/O use case), it uses a single bit in the physical address to communicate the protected/shared attribute of the given page. In the x86 ARCH code, __PHYSICAL_MASK macro represents the width of the physical address in the given architecture. It is used in creating physical PAGE_MASK for address bits in the kernel. Since in TDX guest, a single bit is used as metadata, it needs to be excluded from valid physical address bits to avoid using incorrect addresses bits in the kernel. Enable DYNAMIC_PHYSICAL_MASK to support updating the __PHYSICAL_MASK. Co-developed-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Andi Kleen Reviewed-by: Tony Luck Reviewed-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20220405232939.73860-6-kirill.shutemov@linux.intel.com --- arch/x86/Kconfig | 1 + arch/x86/coco/tdx/tdx.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 984315ca0275..aea4cc404c31 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -883,6 +883,7 @@ config INTEL_TDX_GUEST depends on X86_64 && CPU_SUP_INTEL depends on X86_X2APIC select ARCH_HAS_CC_PLATFORM + select DYNAMIC_PHYSICAL_MASK help Support running as a guest under Intel TDX. Without this support, the guest kernel can not boot or run under TDX. diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 96b2611baac5..e84f6dd3ed2a 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -89,5 +89,13 @@ void __init tdx_early_init(void) cc_mask = get_cc_mask(); cc_set_mask(cc_mask); + /* + * All bits above GPA width are reserved and kernel treats shared bit + * as flag, not as part of physical address. + * + * Adjust physical mask to only cover valid GPA bits. + */ + physical_mask &= cc_mask - 1; + pr_info("Guest detected\n"); } -- cgit v1.2.3