Subject: [PATCH 3/7] KVM: arm/arm64: Condition cache maintenance on unmap with a flag

From: Marc Zyngier <[email-masked]>
Date: Fri, 13 Dec 2019 18:24:59 +0000

In order to allow the elision of cache maintenance operations
on unmap, add a new flag (KVM_UNMAP_ELIDE_CMO) that a caller
can use to indicate that CMOs are not required.

Nobody is passing this flag yet, hence no functional change.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 virt/kvm/arm/mmu.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 0fed7c19c6d5..ebf8c87cc007 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -35,6 +35,9 @@ static unsigned long io_map_base;
 
 #define hyp_pgd_order get_order(PTRS_PER_PGD * sizeof(pgd_t))
 
+/* Flags controlling S2 unmapping */
+#define KVM_UNMAP_ELIDE_CMO		(1UL << 0)
+
 #define KVM_S2PTE_FLAG_IS_IOMAP		(1UL << 0)
 #define KVM_S2_FLAG_LOGGING_ACTIVE	(1UL << 1)
 
@@ -253,7 +256,8 @@ static void unmap_stage2_ptes(struct kvm *kvm, pmd_t *pmd,
 			kvm_tlb_flush_vmid_ipa(kvm, addr);
 
 			/* No need to invalidate the cache for device mappings */
-			if (!kvm_is_device_pfn(pte_pfn(old_pte)))
+			if (!kvm_is_device_pfn(pte_pfn(old_pte)) &&
+			    !(flags & KVM_UNMAP_ELIDE_CMO))
 				kvm_flush_dcache_pte(old_pte);
 
 			put_page(virt_to_page(pte));
@@ -281,7 +285,8 @@ static void unmap_stage2_pmds(struct kvm *kvm, pud_t *pud,
 				pmd_clear(pmd);
 				kvm_tlb_flush_vmid_ipa(kvm, addr);
 
-				kvm_flush_dcache_pmd(old_pmd);
+				if (!(flags & KVM_UNMAP_ELIDE_CMO))
+					kvm_flush_dcache_pmd(old_pmd);
 
 				put_page(virt_to_page(pmd));
 			} else {
@@ -310,7 +315,8 @@ static void unmap_stage2_puds(struct kvm *kvm, pgd_t *pgd,
 
 				stage2_pud_clear(kvm, pud);
 				kvm_tlb_flush_vmid_ipa(kvm, addr);
-				kvm_flush_dcache_pud(old_pud);
+				if (!(flags & KVM_UNMAP_ELIDE_CMO))
+					kvm_flush_dcache_pud(old_pud);
 				put_page(virt_to_page(pud));
 			} else {
 				unmap_stage2_pmds(kvm, pud, addr, next, flags);
-- 
2.20.1

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