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[79.183.34.164]) by smtp.gmail.com with ESMTPSA id q5sm2936471qkf.14.2020.01.09.05.06.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2020 05:06:31 -0800 (PST) Date: Thu, 9 Jan 2020 08:06:25 -0500 From: "Michael S. Tsirkin" To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 2/2] hyperv/synic: Allocate as ram_device Message-ID: <20200109080412-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> <20200109071454-mutt-send-email-mst@kernel.org> <20200109122237.GD6795@work-vm> MIME-Version: 1.0 In-Reply-To: <20200109122237.GD6795@work-vm> X-MC-Unique: DMNQZ7m8NEKlAuTNWaZu7g-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: 207.211.31.120 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 12:22:37PM +0000, Dr. David Alan Gilbert wrote: > * Michael S. Tsirkin (mst@redhat.com) wrote: > > 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 (g= it) 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 mapped > > > > * into the VM address space and access to the region will modify m= emory > > > > * directly. However, the memory region should not be included in = a memory > > > > * dump (device may not be enabled/mapped at the time of the dump),= and > > > > * operations incompatible with manipulating MMIO should be avoided= . Replaces > > > > * 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 d= o > > > it? > > > This clearly isn't normal RAM. > > >=20 > > > Dave > >=20 > > If it's just an optimization for vhost/postcopy/etc, then I think >=20 > Note it's not an optimisation; postcopy fails unless you can aggregate > the members of the hugepage. > And I think vhost-user will fail if you have too many sections - and > the 16 sections from synic I think will blow the slots available. Right, so both are internal reasons. > > 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 > Do we want a new memory_region_init for that or just to be able to add > a flag? >=20 > Dave I think a flag API is preferable since this can apply to any kind of region. But can go either way, Paolo's the maintainer there. > > > >=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, E= rror **errp) > > > > > msgp_name =3D g_strdup_printf("synic-%u-msg-page", vp_index)= ; > > > > > eventp_name =3D g_strdup_printf("synic-%u-event-page", vp_in= dex); > > > > > =20 > > > > > - memory_region_init_ram(&synic->msg_page_mr, obj, msgp_name, > > > > > - sizeof(*synic->msg_page), &error_abor= t); > > > > > - memory_region_init_ram(&synic->event_page_mr, obj, eventp_na= me, > > > > > - sizeof(*synic->event_page), &error_ab= ort); > > > > > - synic->msg_page =3D memory_region_get_ram_ptr(&synic->msg_pa= ge_mr); > > > > > - synic->event_page =3D memory_region_get_ram_ptr(&synic->even= t_page_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= , eventp_name, > > > > > + sizeof(*synic->event_page), synic->ev= ent_page); > > > > > =20 > > > > > g_free(msgp_name); > > > > > g_free(eventp_name); > > > > > --=20 > > > > > 2.24.1 > > > >=20 > > > -- > > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > >=20 > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK