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From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Cc:     David Rientjes <rientjes@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Will Drewry <wad@chromium.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        "Kleen, Andi" <andi.kleen@intel.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [RFC 05/16] x86/kvm: Make VirtIO use DMA API in KVM guest
Date:   Fri, 22 May 2020 15:52:03 +0300
Message-Id: <20200522125214.31348-6-kirill.shutemov@linux.intel.com>
In-Reply-To: <20200522125214.31348-1-kirill.shutemov@linux.intel.com>
References: <20200522125214.31348-1-kirill.shutemov@linux.intel.com>
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VirtIO for KVM is a primary way to provide IO. All memory that used for
communication with the host has to be marked as shared.

The easiest way to archive that is to use DMA API that already knows how
to deal with shared memory.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 drivers/virtio/virtio_ring.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 58b96baa8d48..bd9c56160107 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -12,6 +12,7 @@
 #include <linux/hrtimer.h>
 #include <linux/dma-mapping.h>
 #include <xen/xen.h>
+#include <asm/kvm_para.h>
 
 #ifdef DEBUG
 /* For development, we want to crash whenever the ring is screwed. */
@@ -255,6 +256,9 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
 	if (xen_domain())
 		return true;
 
+	if (kvm_mem_protected())
+		return true;
+
 	return false;
 }
 
-- 
2.26.2