linux-kernel - [PATCH v4 2/2] KVM: s390: prepare for hugepage vmalloc

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Date:   Mon, 14 Jun 2021 15:23:57 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        frankja@...ux.ibm.com, borntraeger@...ibm.com, cohuck@...hat.com,
        david@...hat.com, linux-mm@...ck.org,
        Nicholas Piggin <npiggin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Christoph Hellwig <hch@...radead.org>
Subject: [PATCH v4 2/2] KVM: s390: prepare for hugepage vmalloc

The Create Secure Configuration Ultravisor Call does not support using
large pages for the virtual memory area. This is a hardware limitation.

This patch replaces the vzalloc call with an almost equivalent call to
the newly introduced vmalloc_no_huge function, which guarantees that
only small pages will be used for the backing.

The new call will not clear the allocated memory, but that has never
been an actual requirement.

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
Acked-by: Nicholas Piggin <npiggin@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Uladzislau Rezki (Sony) <urezki@...il.com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Christoph Hellwig <hch@...radead.org>
---
 arch/s390/kvm/pv.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 813b6e93dc83..c8841f476e91 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -140,7 +140,12 @@ static int kvm_s390_pv_alloc_vm(struct kvm *kvm)
 	/* Allocate variable storage */
 	vlen = ALIGN(virt * ((npages * PAGE_SIZE) / HPAGE_SIZE), PAGE_SIZE);
 	vlen += uv_info.guest_virt_base_stor_len;
-	kvm->arch.pv.stor_var = vzalloc(vlen);
+	/*
+	 * The Create Secure Configuration Ultravisor Call does not support
+	 * using large pages for the virtual memory area.
+	 * This is a hardware limitation.
+	 */
+	kvm->arch.pv.stor_var = vmalloc_no_huge(vlen);
 	if (!kvm->arch.pv.stor_var)
 		goto out_err;
 	return 0;
-- 
2.31.1