Patch-mainline: v5.19-rc1
Git-commit: 65fab5bc033aad1a9faf976caec46558c2f88319
References: jsc#PED-342
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Wed, 6 Apr 2022 02:29:14 +0300
Subject: [PATCH] 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 <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20220405232939.73860-6-kirill.shutemov@linux.intel.com
Signed-off-by: Juergen Gross <jgross@suse.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");
}
--
2.35.3