linux-kernel - [PATCH v4 4/7] KVM: arm64: Support PUD hugepage in stage2_is

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Date:   Thu,  5 Jul 2018 15:08:47 +0100
From:   Punit Agrawal <punit.agrawal@....com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Punit Agrawal <punit.agrawal@....com>,
        linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        christoffer.dall@....com, linux-kernel@...r.kernel.org,
        suzuki.poulose@....com, Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH v4 4/7] KVM: arm64: Support PUD hugepage in stage2_is_exec()

In preparation for creating PUD hugepages at stage 2, add support for
detecting execute permissions on PUD page table entries. Faults due to
lack of execute permissions on page table entries is used to perform
i-cache invalidation on first execute.

Provide trivial implementations of arm32 helpers to allow sharing of
code.

Signed-off-by: Punit Agrawal <punit.agrawal@....com>
Cc: Christoffer Dall <christoffer.dall@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Russell King <linux@...linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
---
 arch/arm/include/asm/kvm_mmu.h         |  6 ++++++
 arch/arm64/include/asm/kvm_mmu.h       |  5 +++++
 arch/arm64/include/asm/pgtable-hwdef.h |  2 ++
 virt/kvm/arm/mmu.c                     | 10 +++++++++-
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index c23722f75d5c..d05c8986e495 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -96,6 +96,12 @@ static inline bool kvm_s2pud_readonly(pud_t *pud)
 }
 
 
+static inline bool kvm_s2pud_exec(pud_t *pud)
+{
+	BUG();
+	return false;
+}
+
 static inline void kvm_set_pmd(pmd_t *pmd, pmd_t new_pmd)
 {
 	*pmd = new_pmd;
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 84051930ddfe..15bc1be8f82f 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -249,6 +249,11 @@ static inline bool kvm_s2pud_readonly(pud_t *pudp)
 	return kvm_s2pte_readonly((pte_t *)pudp);
 }
 
+static inline bool kvm_s2pud_exec(pud_t *pudp)
+{
+	return !(READ_ONCE(pud_val(*pudp)) & PUD_S2_XN);
+}
+
 static inline bool kvm_page_empty(void *ptr)
 {
 	struct page *ptr_page = virt_to_page(ptr);
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index fd208eac9f2a..10ae592b78b8 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -193,6 +193,8 @@
 #define PMD_S2_RDWR		(_AT(pmdval_t, 3) << 6)   /* HAP[2:1] */
 #define PMD_S2_XN		(_AT(pmdval_t, 2) << 53)  /* XN[1:0] */
 
+#define PUD_S2_XN		(_AT(pudval_t, 2) << 53)  /* XN[1:0] */
+
 /*
  * Memory Attribute override for Stage-2 (MemAttr[3:0])
  */
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index db04b18218c1..ccdea0edabb3 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1040,10 +1040,18 @@ static int stage2_set_pmd_huge(struct kvm *kvm, struct kvm_mmu_memory_cache
 
 static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
 {
+	pud_t *pudp;
 	pmd_t *pmdp;
 	pte_t *ptep;
 
-	pmdp = stage2_get_pmd(kvm, NULL, addr);
+	pudp = stage2_get_pud(kvm, NULL, addr);
+	if (!pudp || pud_none(*pudp) || !pud_present(*pudp))
+		return false;
+
+	if (pud_huge(*pudp))
+		return kvm_s2pud_exec(pudp);
+
+	pmdp = stage2_pmd_offset(pudp, addr);
 	if (!pmdp || pmd_none(*pmdp) || !pmd_present(*pmdp))
 		return false;
 
-- 
2.17.1