linux-kernel - [PATCH v5.5 17/30] KVM: s390: Skip gfn/size sanity checks on memslot DELETE or FLAGS

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Date:   Thu,  4 Nov 2021 00:25:18 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Marc Zyngier <maz@...nel.org>, Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Paul Mackerras <paulus@...abs.org>,
        Anup Patel <anup.patel@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Atish Patra <atish.patra@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Ben Gardon <bgardon@...gle.com>,
        "Maciej S . Szmigiero" <maciej.szmigiero@...cle.com>
Subject: [PATCH v5.5 17/30] KVM: s390: Skip gfn/size sanity checks on memslot
 DELETE or FLAGS_ONLY

Sanity check the hva, gfn, and size of a userspace memory region only if
any of those properties can change, i.e. skip the checks for DELETE and
FLAGS_ONLY.  KVM doesn't allow moving the hva or changing the size, a gfn
change shows up as a MOVE even if flags are being modified, and the
checks are pointless for the DELETE case as userspace_addr and gfn_base
are zeroed by common KVM.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/s390/kvm/kvm-s390.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 81f90891db0f..c4d0ed5f3400 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5020,7 +5020,14 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *new,
 				   enum kvm_mr_change change)
 {
-	gpa_t size = new->npages * PAGE_SIZE;
+	gpa_t size;
+
+	/* When we are protected, we should not change the memory slots */
+	if (kvm_s390_pv_get_handle(kvm))
+		return -EINVAL;
+
+	if (change == KVM_MR_DELETE || change == KVM_MR_FLAGS_ONLY)
+		return 0;
 
 	/* A few sanity checks. We can have memory slots which have to be
 	   located/ended at a segment boundary (1MB). The memory in userland is
@@ -5030,15 +5037,13 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	if (new->userspace_addr & 0xffffful)
 		return -EINVAL;
 
+	size = new->npages * PAGE_SIZE;
 	if (size & 0xffffful)
 		return -EINVAL;
 
 	if ((new->base_gfn * PAGE_SIZE) + size > kvm->arch.mem_limit)
 		return -EINVAL;
 
-	/* When we are protected, we should not change the memory slots */
-	if (kvm_s390_pv_get_handle(kvm))
-		return -EINVAL;
 	return 0;
 }
 
-- 
2.33.1.1089.g2158813163f-goog