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[79.183.34.164]) by smtp.gmail.com with ESMTPSA id z12sm2431277qts.97.2020.01.09.04.18.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2020 04:18:43 -0800 (PST) Date: Thu, 9 Jan 2020 07:18:39 -0500 From: "Michael S. Tsirkin" To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 2/2] hyperv/synic: Allocate as ram_device Message-ID: <20200109071454-mutt-send-email-mst@kernel.org> References: <20200108135353.75471-1-dgilbert@redhat.com> <20200108135353.75471-3-dgilbert@redhat.com> <20200109064527-mutt-send-email-mst@kernel.org> <20200109120820.GB6795@work-vm> MIME-Version: 1.0 In-Reply-To: <20200109120820.GB6795@work-vm> X-MC-Unique: zRWoMG06NmGfi9R2BImNxg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jasowang@redhat.com, vkuznets@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jan 09, 2020 at 12:08:20PM +0000, Dr. David Alan Gilbert wrote: > * Michael S. Tsirkin (mst@redhat.com) wrote: > > On Wed, Jan 08, 2020 at 01:53:53PM +0000, Dr. David Alan Gilbert (git) = wrote: > > > From: "Dr. David Alan Gilbert" > > >=20 > > > Mark the synic pages as ram_device so that they won't be visible > > > to vhost. > > >=20 > > > Signed-off-by: Dr. David Alan Gilbert > >=20 > >=20 > > I think I disagree with this one. > > * A RAM device represents a mapping to a physical device, such as to a= PCI > > * MMIO BAR of an vfio-pci assigned device. The memory region may be m= apped > > * into the VM address space and access to the region will modify memor= y > > * directly. However, the memory region should not be included in a me= mory > > * dump (device may not be enabled/mapped at the time of the dump), and > > * operations incompatible with manipulating MMIO should be avoided. R= eplaces > > * skip_dump flag. > >=20 > > Looks like an abuse of notation. >=20 > OK, it did feel a bit like that - any suggestions of another way to do > it? > This clearly isn't normal RAM. >=20 > Dave If it's just an optimization for vhost/postcopy/etc, then I think an API that says how this isn't normal ram would be ok. E.g. it's not DMA'd into? Then maybe _nodma? > >=20 > >=20 > > > --- > > > hw/hyperv/hyperv.c | 14 ++++++++------ > > > 1 file changed, 8 insertions(+), 6 deletions(-) > > >=20 > > > diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c > > > index da8ce82725..4de3ec411d 100644 > > > --- a/hw/hyperv/hyperv.c > > > +++ b/hw/hyperv/hyperv.c > > > @@ -95,12 +95,14 @@ static void synic_realize(DeviceState *dev, Error= **errp) > > > msgp_name =3D g_strdup_printf("synic-%u-msg-page", vp_index); > > > eventp_name =3D g_strdup_printf("synic-%u-event-page", vp_index)= ; > > > =20 > > > - memory_region_init_ram(&synic->msg_page_mr, obj, msgp_name, > > > - sizeof(*synic->msg_page), &error_abort); > > > - memory_region_init_ram(&synic->event_page_mr, obj, eventp_name, > > > - sizeof(*synic->event_page), &error_abort)= ; > > > - synic->msg_page =3D memory_region_get_ram_ptr(&synic->msg_page_m= r); > > > - synic->event_page =3D memory_region_get_ram_ptr(&synic->event_pa= ge_mr); > > > + synic->msg_page =3D qemu_memalign(qemu_real_host_page_size, > > > + sizeof(*synic->msg_page)); > > > + synic->event_page =3D qemu_memalign(qemu_real_host_page_size, > > > + sizeof(*synic->event_page)); > > > + memory_region_init_ram_device_ptr(&synic->msg_page_mr, obj, msgp= _name, > > > + sizeof(*synic->msg_page), synic->msg_page= ); > > > + memory_region_init_ram_device_ptr(&synic->event_page_mr, obj, ev= entp_name, > > > + sizeof(*synic->event_page), synic->event_= page); > > > =20 > > > g_free(msgp_name); > > > g_free(eventp_name); > > > --=20 > > > 2.24.1 > >=20 > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK