linux-kernel - [PATCH, RFC 07/62] x86/mm: Mask out KeyID bits from page table entry pfn

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Date:   Wed,  8 May 2019 17:43:27 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH, RFC 07/62] x86/mm: Mask out KeyID bits from page table entry pfn

MKTME claims several upper bits of the physical address in a page table
entry to encode KeyID. It effectively shrinks number of bits for
physical address. We should exclude KeyID bits from physical addresses.

For instance, if CPU enumerates 52 physical address bits and number of
bits claimed for KeyID is 6, bits 51:46 must not be threated as part
physical address.

This patch adjusts __PHYSICAL_MASK during MKTME enumeration.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/kernel/cpu/intel.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 3142fd7a9b32..5dfecc9c2253 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -589,6 +589,29 @@ static void detect_tme(struct cpuinfo_x86 *c)
 		mktme_status = MKTME_ENABLED;
 	}
 
+#ifdef CONFIG_X86_INTEL_MKTME
+	if (mktme_status == MKTME_ENABLED && nr_keyids) {
+		/*
+		 * Mask out bits claimed from KeyID from physical address mask.
+		 *
+		 * For instance, if a CPU enumerates 52 physical address bits
+		 * and number of bits claimed for KeyID is 6, bits 51:46 of
+		 * physical address is unusable.
+		 */
+		phys_addr_t keyid_mask;
+
+		keyid_mask = GENMASK_ULL(c->x86_phys_bits - 1, c->x86_phys_bits - keyid_bits);
+		physical_mask &= ~keyid_mask;
+	} else {
+		/*
+		 * Reset __PHYSICAL_MASK.
+		 * Maybe needed if there's inconsistent configuation
+		 * between CPUs.
+		 */
+		physical_mask = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
+	}
+#endif
+
 	/*
 	 * KeyID bits effectively lower the number of physical address
 	 * bits.  Update cpuinfo_x86::x86_phys_bits accordingly.
-- 
2.20.1