linux-kernel - [PATCH 1/2] x86: mm: Allow PTI helpers to be used outside x86/mm

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Date:   Mon, 22 Aug 2022 13:12:12 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        x86@...nel.org, Joerg Roedel <joro@...tes.org>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>
Cc:     Raj Ashok <ashok.raj@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...el.com>,
        "Borislav Petkov" <bp@...en8.de>, "Ingo Molnar" <mingo@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH 1/2] x86: mm: Allow PTI helpers to be used outside x86/mm

With the support of shared virtual addressing(SVA), x86 IOMMUs also
need to get access to user PGD when sharing user mappings.

This patch makes sure the PTI helper function to retrieve user PGD
is available regardless the state of CONFIG_PAGE_TABLE_ISOLATION.
So far, such need is x86 only.

Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 arch/x86/include/asm/pgtable.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 44e2d6f1dbaa..42f55281e232 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1227,6 +1227,11 @@ static inline p4d_t *user_to_kernel_p4dp(p4d_t *p4dp)
 {
 	return ptr_clear_bit(p4dp, PTI_PGTABLE_SWITCH_BIT);
 }
+#else
+static inline pgd_t *kernel_to_user_pgdp(pgd_t *pgdp)
+{
+	return pgdp;
+}
 #endif /* CONFIG_PAGE_TABLE_ISOLATION */
 
 /*
-- 
2.25.1