linux-kernel - [RFC v1 22/26] x86/tdx: Exclude Shared bit from __PHYSICAL

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Date:   Fri,  5 Feb 2021 15:38:39 -0800
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [RFC v1 22/26] x86/tdx: Exclude Shared bit from __PHYSICAL_MASK

From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

tdx_shared_mask() returns the mask that has to be set in page table
entry to make page shared with VMM.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---
 arch/x86/Kconfig           | 1 +
 arch/x86/include/asm/tdx.h | 1 +
 arch/x86/kernel/tdx.c      | 8 ++++++++
 3 files changed, 10 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8fa654d61ac2..f10a00c4ad7f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -875,6 +875,7 @@ config INTEL_TDX_GUEST
 	select PARAVIRT_XL
 	select X86_X2APIC
 	select SECURITY_LOCKDOWN_LSM
+	select X86_MEM_ENCRYPT_COMMON
 	help
 	  Provide support for running in a trusted domain on Intel processors
 	  equipped with Trusted Domain eXtenstions. TDX is an new Intel
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index b46ae140e39b..9bbfe6520ea4 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -104,5 +104,6 @@ long tdx_kvm_hypercall3(unsigned int nr, unsigned long p1, unsigned long p2,
 long tdx_kvm_hypercall4(unsigned int nr, unsigned long p1, unsigned long p2,
 		unsigned long p3, unsigned long p4);
 
+phys_addr_t tdx_shared_mask(void);
 #endif
 #endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index ae37498df981..9681f4a0b4e0 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -41,6 +41,11 @@ bool is_tdx_guest(void)
 }
 EXPORT_SYMBOL_GPL(is_tdx_guest);
 
+phys_addr_t tdx_shared_mask(void)
+{
+	return 1ULL << (td_info.gpa_width - 1);
+}
+
 static void tdx_get_info(void)
 {
 	register long rcx asm("rcx");
@@ -56,6 +61,9 @@ static void tdx_get_info(void)
 
 	td_info.gpa_width = rcx & GENMASK(5, 0);
 	td_info.attributes = rdx;
+
+	/* Exclude Shared bit from the __PHYSICAL_MASK */
+	physical_mask &= ~tdx_shared_mask();
 }
 
 static __cpuidle void tdx_halt(void)
-- 
2.25.1