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[PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid

MingWang Li posted 1 patch 2 years, 6 months ago
Test checkpatch passed
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20211012014501.24996-1-limingwang@huawei.com
Maintainers: Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Bin Meng <bin.meng@windriver.com>
hw/riscv/virt.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
[PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by MingWang Li 2 years, 6 months ago 
From: Mingwang Li <limingwang@huawei.com>

When I start the VM with the following command:
$ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
    -name guest=riscv-guset \
    -smp 2 \
    -bios none \
    -kernel ./Image \
    -drive file=./guest.img,format=raw,id=hd0 \
    -device virtio-blk-device,drive=hd0 \
    -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
    -object memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \
    -numa node,memdev=mem -mem-prealloc \
    -chardev socket,id=char0,path=/mnt/vhost-net0 \
    -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
    -device virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=on,guest_csum=on,guest_ecn=on \

Then, QEMU displays the following error information:
qemu-system-riscv64: Failed initializing vhost-user memory map, consider using -object memory-backend-file share=on
qemu-system-riscv64: vhost_set_mem_table failed: Interrupted system call (4)
qemu-system-riscv64: unable to start vhost net: 4: falling back on userspace virtio

Note that, before starting the kvm-acceled QEMU VM, following
temporarily unaccepted QEMU patches should be used:
https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg02516.html

This error was made bacause default main_mem is used to be registered
as the system memory, other memory cannot be initialized. Therefore,
the system memory should be initialized to the machine->ram, which
consists of the default main_mem and other possible memory required
by applications, such as shared hugepage memory in DPDK.
Also, the mc->defaul_ram_id should be set to the default main_mem,
such as "riscv_virt_board.ram" for the virt machine.

Signed-off-by: Mingwang Li <limingwang@huawei.com>
Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 hw/riscv/virt.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index ec0cb69b8c..b3b431c847 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -771,7 +771,6 @@ static void virt_machine_init(MachineState *machine)
     const MemMapEntry *memmap = virt_memmap;
     RISCVVirtState *s = RISCV_VIRT_MACHINE(machine);
     MemoryRegion *system_memory = get_system_memory();
-    MemoryRegion *main_mem = g_new(MemoryRegion, 1);
     MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
     char *plic_hart_config, *soc_name;
     target_ulong start_addr = memmap[VIRT_DRAM].base;
@@ -890,10 +889,8 @@ static void virt_machine_init(MachineState *machine)
     }
 
     /* register system main memory (actual RAM) */
-    memory_region_init_ram(main_mem, NULL, "riscv_virt_board.ram",
-                           machine->ram_size, &error_fatal);
     memory_region_add_subregion(system_memory, memmap[VIRT_DRAM].base,
-        main_mem);
+        machine->ram);
 
     /* create device tree */
     create_fdt(s, memmap, machine->ram_size, machine->kernel_cmdline,
@@ -1032,6 +1029,7 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
     mc->cpu_index_to_instance_props = riscv_numa_cpu_index_to_props;
     mc->get_default_cpu_node_id = riscv_numa_get_default_cpu_node_id;
     mc->numa_mem_supported = true;
+    mc->default_ram_id = "riscv_virt_board.ram";
 
     machine_class_allow_dynamic_sysbus_dev(mc, TYPE_RAMFB_DEVICE);
 
-- 
2.19.1
Re: [PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by Bin Meng 2 years, 6 months ago 
On Tue, Oct 12, 2021 at 9:46 AM MingWang Li <limingwang@huawei.com> wrote:
>
> From: Mingwang Li <limingwang@huawei.com>
>
> When I start the VM with the following command:
> $ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
>     -name guest=riscv-guset \
>     -smp 2 \
>     -bios none \
>     -kernel ./Image \
>     -drive file=./guest.img,format=raw,id=hd0 \
>     -device virtio-blk-device,drive=hd0 \
>     -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
>     -object memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \
>     -numa node,memdev=mem -mem-prealloc \
>     -chardev socket,id=char0,path=/mnt/vhost-net0 \
>     -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
>     -device virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=on,guest_csum=on,guest_ecn=on \
>
> Then, QEMU displays the following error information:
> qemu-system-riscv64: Failed initializing vhost-user memory map, consider using -object memory-backend-file share=on

I see your command line parameters already contain "-object
memory-backend-file share=on", so this error message is not accurate.
Should this message be altered to mention things like what this patch
does?

> qemu-system-riscv64: vhost_set_mem_table failed: Interrupted system call (4)
> qemu-system-riscv64: unable to start vhost net: 4: falling back on userspace virtio
>
> Note that, before starting the kvm-acceled QEMU VM, following
> temporarily unaccepted QEMU patches should be used:
> https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg02516.html
>
> This error was made bacause default main_mem is used to be registered

typo: because

> as the system memory, other memory cannot be initialized. Therefore,
> the system memory should be initialized to the machine->ram, which
> consists of the default main_mem and other possible memory required
> by applications, such as shared hugepage memory in DPDK.
> Also, the mc->defaul_ram_id should be set to the default main_mem,
> such as "riscv_virt_board.ram" for the virt machine.
>

How about changing the commit title to: "Use machine->ram as the
system memory" ??

> Signed-off-by: Mingwang Li <limingwang@huawei.com>
> Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
> ---
>  hw/riscv/virt.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index ec0cb69b8c..b3b431c847 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -771,7 +771,6 @@ static void virt_machine_init(MachineState *machine)
>      const MemMapEntry *memmap = virt_memmap;
>      RISCVVirtState *s = RISCV_VIRT_MACHINE(machine);
>      MemoryRegion *system_memory = get_system_memory();
> -    MemoryRegion *main_mem = g_new(MemoryRegion, 1);
>      MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
>      char *plic_hart_config, *soc_name;
>      target_ulong start_addr = memmap[VIRT_DRAM].base;
> @@ -890,10 +889,8 @@ static void virt_machine_init(MachineState *machine)
>      }
>
>      /* register system main memory (actual RAM) */
> -    memory_region_init_ram(main_mem, NULL, "riscv_virt_board.ram",
> -                           machine->ram_size, &error_fatal);
>      memory_region_add_subregion(system_memory, memmap[VIRT_DRAM].base,
> -        main_mem);
> +        machine->ram);
>
>      /* create device tree */
>      create_fdt(s, memmap, machine->ram_size, machine->kernel_cmdline,
> @@ -1032,6 +1029,7 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
>      mc->cpu_index_to_instance_props = riscv_numa_cpu_index_to_props;
>      mc->get_default_cpu_node_id = riscv_numa_get_default_cpu_node_id;
>      mc->numa_mem_supported = true;
> +    mc->default_ram_id = "riscv_virt_board.ram";
>
>      machine_class_allow_dynamic_sysbus_dev(mc, TYPE_RAMFB_DEVICE);
>

Regards,
Bin
RE: [PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by limingwang (A) 2 years, 6 months ago 
On Wed, Oct 13, 2021 at 22:41 PM Bin Meng <bin.meng@windriver.com> wrote:
> 
> On Tue, Oct 12, 2021 at 9:46 AM MingWang Li <limingwang@huawei.com> wrote:
> >
> > From: Mingwang Li <limingwang@huawei.com>
> >
> > When I start the VM with the following command:
> > $ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
> >     -name guest=riscv-guset \
> >     -smp 2 \
> >     -bios none \
> >     -kernel ./Image \
> >     -drive file=./guest.img,format=raw,id=hd0 \
> >     -device virtio-blk-device,drive=hd0 \
> >     -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
> >     -object
> memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \
> >     -numa node,memdev=mem -mem-prealloc \
> >     -chardev socket,id=char0,path=/mnt/vhost-net0 \
> >     -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
> >     -device
> > virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=o
> > n,guest_csum=on,guest_ecn=on \
> >
> > Then, QEMU displays the following error information:
> > qemu-system-riscv64: Failed initializing vhost-user memory map,
> > consider using -object memory-backend-file share=on
> 
> I see your command line parameters already contain "-object memory-backend-file
> share=on", so this error message is not accurate.

QEMU uses this command to alloc fd in the "memory_region_init_ram_from_file" function
and assigns the value of fd to mr->ram_block-fd. If the QEMU uses the default memory to
initialize the system, the QEMU cannot obtain the fd in the "vhost_user_mem_section_filter" 
function when initializing the vhost-user. As a result, an error is reported in the "vhost_user_fill_set_mem_table_msg"
function.

Because of the above bug, even if "-object memory-backend-file share=on" is added to the command line,
the QEMU still reports an error.
This patch can solve this bug.

> Should this message be altered to mention things like what this patch does?

Thanks, I will rewrite the message in next version.
> 
> > qemu-system-riscv64: vhost_set_mem_table failed: Interrupted system
> > call (4)
> > qemu-system-riscv64: unable to start vhost net: 4: falling back on
> > userspace virtio
> >
> > Note that, before starting the kvm-acceled QEMU VM, following
> > temporarily unaccepted QEMU patches should be used:
> > https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg02516.html
> >
> > This error was made bacause default main_mem is used to be registered
> 
> typo: because
> 
Thanks.

> > as the system memory, other memory cannot be initialized. Therefore,
> > the system memory should be initialized to the machine->ram, which
> > consists of the default main_mem and other possible memory required by
> > applications, such as shared hugepage memory in DPDK.
> > Also, the mc->defaul_ram_id should be set to the default main_mem,
> > such as "riscv_virt_board.ram" for the virt machine.
> >
> 
> How about changing the commit title to: "Use machine->ram as the system
> memory" ??
> 

I think it is just a bugfix.

> > Signed-off-by: Mingwang Li <limingwang@huawei.com>
> > Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
> > Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
> > ---
> >  hw/riscv/virt.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c index
> > ec0cb69b8c..b3b431c847 100644
> > --- a/hw/riscv/virt.c
> > +++ b/hw/riscv/virt.c
> > @@ -771,7 +771,6 @@ static void virt_machine_init(MachineState *machine)
> >      const MemMapEntry *memmap = virt_memmap;
> >      RISCVVirtState *s = RISCV_VIRT_MACHINE(machine);
> >      MemoryRegion *system_memory = get_system_memory();
> > -    MemoryRegion *main_mem = g_new(MemoryRegion, 1);
> >      MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
> >      char *plic_hart_config, *soc_name;
> >      target_ulong start_addr = memmap[VIRT_DRAM].base; @@ -890,10
> > +889,8 @@ static void virt_machine_init(MachineState *machine)
> >      }
> >
> >      /* register system main memory (actual RAM) */
> > -    memory_region_init_ram(main_mem, NULL, "riscv_virt_board.ram",
> > -                           machine->ram_size, &error_fatal);
> >      memory_region_add_subregion(system_memory,
> memmap[VIRT_DRAM].base,
> > -        main_mem);
> > +        machine->ram);
> >
> >      /* create device tree */
> >      create_fdt(s, memmap, machine->ram_size, machine->kernel_cmdline,
> > @@ -1032,6 +1029,7 @@ static void virt_machine_class_init(ObjectClass *oc,
> void *data)
> >      mc->cpu_index_to_instance_props = riscv_numa_cpu_index_to_props;
> >      mc->get_default_cpu_node_id = riscv_numa_get_default_cpu_node_id;
> >      mc->numa_mem_supported = true;
> > +    mc->default_ram_id = "riscv_virt_board.ram";
> >
> >      machine_class_allow_dynamic_sysbus_dev(mc, TYPE_RAMFB_DEVICE);
> >
> 
> Regards,
> Bin
Re: [PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by Bin Meng 2 years, 6 months ago 
On Fri, Oct 15, 2021 at 4:52 PM limingwang (A) <limingwang@huawei.com> wrote:
>
>
> On Wed, Oct 13, 2021 at 22:41 PM Bin Meng <bin.meng@windriver.com> wrote:
> >
> > On Tue, Oct 12, 2021 at 9:46 AM MingWang Li <limingwang@huawei.com> wrote:
> > >
> > > From: Mingwang Li <limingwang@huawei.com>
> > >
> > > When I start the VM with the following command:
> > > $ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
> > >     -name guest=riscv-guset \
> > >     -smp 2 \
> > >     -bios none \
> > >     -kernel ./Image \
> > >     -drive file=./guest.img,format=raw,id=hd0 \
> > >     -device virtio-blk-device,drive=hd0 \
> > >     -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
> > >     -object
> > memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \
> > >     -numa node,memdev=mem -mem-prealloc \
> > >     -chardev socket,id=char0,path=/mnt/vhost-net0 \
> > >     -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
> > >     -device
> > > virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=o
> > > n,guest_csum=on,guest_ecn=on \
> > >
> > > Then, QEMU displays the following error information:
> > > qemu-system-riscv64: Failed initializing vhost-user memory map,
> > > consider using -object memory-backend-file share=on
> >
> > I see your command line parameters already contain "-object memory-backend-file
> > share=on", so this error message is not accurate.
>
> QEMU uses this command to alloc fd in the "memory_region_init_ram_from_file" function
> and assigns the value of fd to mr->ram_block-fd. If the QEMU uses the default memory to
> initialize the system, the QEMU cannot obtain the fd in the "vhost_user_mem_section_filter"
> function when initializing the vhost-user. As a result, an error is reported in the "vhost_user_fill_set_mem_table_msg"
> function.
>
> Because of the above bug, even if "-object memory-backend-file share=on" is added to the command line,
> the QEMU still reports an error.

Yes, what I meant is that QEMU should not report such inaccurate
messages because of some random codes elsewhere.

With current message, it suggested user use "-object
memory-backend-file share=on" in the command line, but it is already
used. So this is a false alarm. The "bug" is somewhere else.

> This patch can solve this bug.
>
> > Should this message be altered to mention things like what this patch does?
>
> Thanks, I will rewrite the message in next version.
> >
> > > qemu-system-riscv64: vhost_set_mem_table failed: Interrupted system
> > > call (4)
> > > qemu-system-riscv64: unable to start vhost net: 4: falling back on
> > > userspace virtio
> > >
> > > Note that, before starting the kvm-acceled QEMU VM, following
> > > temporarily unaccepted QEMU patches should be used:
> > > https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg02516.html
> > >
> > > This error was made bacause default main_mem is used to be registered
> >
> > typo: because
> >
> Thanks.
>
> > > as the system memory, other memory cannot be initialized. Therefore,
> > > the system memory should be initialized to the machine->ram, which
> > > consists of the default main_mem and other possible memory required by
> > > applications, such as shared hugepage memory in DPDK.
> > > Also, the mc->defaul_ram_id should be set to the default main_mem,
> > > such as "riscv_virt_board.ram" for the virt machine.
> > >
> >
> > How about changing the commit title to: "Use machine->ram as the system
> > memory" ??
> >
>
> I think it is just a bugfix.
>

But the current codes run perfectly okay so far. This patch adds an
additional use case for the KVM scenario where current codes cannot
handle.

Regards,
Bin
Re: [PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by Igor Mammedov 2 years, 6 months ago 
On Fri, 15 Oct 2021 17:25:01 +0800
Bin Meng <bmeng.cn@gmail.com> wrote:

> On Fri, Oct 15, 2021 at 4:52 PM limingwang (A) <limingwang@huawei.com> wrote:
> >
> >
> > On Wed, Oct 13, 2021 at 22:41 PM Bin Meng <bin.meng@windriver.com> wrote:  
> > >
> > > On Tue, Oct 12, 2021 at 9:46 AM MingWang Li <limingwang@huawei.com> wrote:  
> > > >
> > > > From: Mingwang Li <limingwang@huawei.com>
> > > >
> > > > When I start the VM with the following command:
> > > > $ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
> > > >     -name guest=riscv-guset \
> > > >     -smp 2 \
> > > >     -bios none \
> > > >     -kernel ./Image \
> > > >     -drive file=./guest.img,format=raw,id=hd0 \
> > > >     -device virtio-blk-device,drive=hd0 \
> > > >     -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
> > > >     -object  
> > > memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \  
> > > >     -numa node,memdev=mem -mem-prealloc \
> > > >     -chardev socket,id=char0,path=/mnt/vhost-net0 \
> > > >     -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
> > > >     -device
> > > > virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=o
> > > > n,guest_csum=on,guest_ecn=on \
> > > >
> > > > Then, QEMU displays the following error information:
> > > > qemu-system-riscv64: Failed initializing vhost-user memory map,
> > > > consider using -object memory-backend-file share=on  
> > >
> > > I see your command line parameters already contain "-object memory-backend-file
> > > share=on", so this error message is not accurate.  
> >
> > QEMU uses this command to alloc fd in the "memory_region_init_ram_from_file" function
> > and assigns the value of fd to mr->ram_block-fd. If the QEMU uses the default memory to
> > initialize the system, the QEMU cannot obtain the fd in the "vhost_user_mem_section_filter"
> > function when initializing the vhost-user. As a result, an error is reported in the "vhost_user_fill_set_mem_table_msg"
> > function.
> >
> > Because of the above bug, even if "-object memory-backend-file share=on" is added to the command line,
> > the QEMU still reports an error.  
> 
> Yes, what I meant is that QEMU should not report such inaccurate
> messages because of some random codes elsewhere.
> 
> With current message, it suggested user use "-object
> memory-backend-file share=on" in the command line, but it is already
> used. So this is a false alarm. The "bug" is somewhere else.

bug is in using memory_region_init_ram(),
which can't possibly handle vhost-user, and can't work as expected with
'-numa node,memdev' options.
Before main ram infrastructure was converted to memdev,
one should have used memory_region_allocate_system_memory() for
allocating main RAM, so numa usecase was broken from the start.
Later it old API was dropped in favor of more flexible/generic
MachineState::ram approach (see commits 68a86dc15ccd..f0530f14c7c35d).


Modulo commit message, patch looks good to me and does what
every machine should do. (I though that I've converted every
existing to generalized MachineState::ram but it looks like
riscv was missed).

So we can model commit message after bd457782b3b0a,
and also add that the patch fixes broken -numa node,memdev case,
which never properly worked. It also opens possibility to
use vhost-user/virtiosf with main RAM if main RAM is
provided explicitly via machine.memory-backend option
with shared memory backend.

Btw: is there other riscv machines that allocate RAM directly?
(if yes, those should be fixed as well, a patch per machine)


> > This patch can solve this bug.
> >  
> > > Should this message be altered to mention things like what this patch does?  
> >
> > Thanks, I will rewrite the message in next version.  
> > >  
> > > > qemu-system-riscv64: vhost_set_mem_table failed: Interrupted system
> > > > call (4)
> > > > qemu-system-riscv64: unable to start vhost net: 4: falling back on
> > > > userspace virtio
> > > >
> > > > Note that, before starting the kvm-acceled QEMU VM, following
> > > > temporarily unaccepted QEMU patches should be used:
> > > > https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg02516.html
> > > >
> > > > This error was made bacause default main_mem is used to be registered  
> > >
> > > typo: because
> > >  
> > Thanks.
> >  
> > > > as the system memory, other memory cannot be initialized. Therefore,
> > > > the system memory should be initialized to the machine->ram, which
> > > > consists of the default main_mem and other possible memory required by
> > > > applications, such as shared hugepage memory in DPDK.
> > > > Also, the mc->defaul_ram_id should be set to the default main_mem,
> > > > such as "riscv_virt_board.ram" for the virt machine.
> > > >  
> > >
> > > How about changing the commit title to: "Use machine->ram as the system
> > > memory" ??
> > >  
> >
> > I think it is just a bugfix.
> >  
> 
> But the current codes run perfectly okay so far. This patch adds an
> additional use case for the KVM scenario where current codes cannot
> handle.
> 
> Regards,
> Bin
>
Re: [PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by Bin Meng 2 years, 6 months ago 
Hi Igor,

On Fri, Oct 15, 2021 at 8:59 PM Igor Mammedov <imammedo@redhat.com> wrote:
>
> On Fri, 15 Oct 2021 17:25:01 +0800
> Bin Meng <bmeng.cn@gmail.com> wrote:
>
> > On Fri, Oct 15, 2021 at 4:52 PM limingwang (A) <limingwang@huawei.com> wrote:
> > >
> > >
> > > On Wed, Oct 13, 2021 at 22:41 PM Bin Meng <bin.meng@windriver.com> wrote:
> > > >
> > > > On Tue, Oct 12, 2021 at 9:46 AM MingWang Li <limingwang@huawei.com> wrote:
> > > > >
> > > > > From: Mingwang Li <limingwang@huawei.com>
> > > > >
> > > > > When I start the VM with the following command:
> > > > > $ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
> > > > >     -name guest=riscv-guset \
> > > > >     -smp 2 \
> > > > >     -bios none \
> > > > >     -kernel ./Image \
> > > > >     -drive file=./guest.img,format=raw,id=hd0 \
> > > > >     -device virtio-blk-device,drive=hd0 \
> > > > >     -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
> > > > >     -object
> > > > memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \
> > > > >     -numa node,memdev=mem -mem-prealloc \
> > > > >     -chardev socket,id=char0,path=/mnt/vhost-net0 \
> > > > >     -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
> > > > >     -device
> > > > > virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=o
> > > > > n,guest_csum=on,guest_ecn=on \
> > > > >
> > > > > Then, QEMU displays the following error information:
> > > > > qemu-system-riscv64: Failed initializing vhost-user memory map,
> > > > > consider using -object memory-backend-file share=on
> > > >
> > > > I see your command line parameters already contain "-object memory-backend-file
> > > > share=on", so this error message is not accurate.
> > >
> > > QEMU uses this command to alloc fd in the "memory_region_init_ram_from_file" function
> > > and assigns the value of fd to mr->ram_block-fd. If the QEMU uses the default memory to
> > > initialize the system, the QEMU cannot obtain the fd in the "vhost_user_mem_section_filter"
> > > function when initializing the vhost-user. As a result, an error is reported in the "vhost_user_fill_set_mem_table_msg"
> > > function.
> > >
> > > Because of the above bug, even if "-object memory-backend-file share=on" is added to the command line,
> > > the QEMU still reports an error.
> >
> > Yes, what I meant is that QEMU should not report such inaccurate
> > messages because of some random codes elsewhere.
> >
> > With current message, it suggested user use "-object
> > memory-backend-file share=on" in the command line, but it is already
> > used. So this is a false alarm. The "bug" is somewhere else.
>
> bug is in using memory_region_init_ram(),
> which can't possibly handle vhost-user, and can't work as expected with
> '-numa node,memdev' options.
> Before main ram infrastructure was converted to memdev,
> one should have used memory_region_allocate_system_memory() for
> allocating main RAM, so numa usecase was broken from the start.
> Later it old API was dropped in favor of more flexible/generic
> MachineState::ram approach (see commits 68a86dc15ccd..f0530f14c7c35d).

Thanks for the detailed pointers.

I wonder if it is possible to make the error message to be clearer, so
instead of having

    "qemu-system-riscv64: Failed initializing vhost-user memory map,
consider using -object memory-backend-file share=on"

can we do:

    "qemu-system-riscv64: Failed initializing vhost-user memory map,
considering using MachineState::ram instead of manually initializing
RAM memory region."

which is more straightforward?

>
>
> Modulo commit message, patch looks good to me and does what
> every machine should do. (I though that I've converted every
> existing to generalized MachineState::ram but it looks like
> riscv was missed).

Indeed all riscv boards are doing the same thing.

>
> So we can model commit message after bd457782b3b0a,
> and also add that the patch fixes broken -numa node,memdev case,
> which never properly worked. It also opens possibility to
> use vhost-user/virtiosf with main RAM if main RAM is
> provided explicitly via machine.memory-backend option
> with shared memory backend.
>
> Btw: is there other riscv machines that allocate RAM directly?
> (if yes, those should be fixed as well, a patch per machine)
>

I will see if I can get some patches to fix other riscv machines.

Regards,
Bin
Re: [PATCH v2] hw/riscv: virt: bugfix the memory-backend-file command is invalid
Posted by Igor Mammedov 2 years, 6 months ago 
On Mon, 18 Oct 2021 10:17:45 +0800
Bin Meng <bmeng.cn@gmail.com> wrote:

> Hi Igor,
> 
> On Fri, Oct 15, 2021 at 8:59 PM Igor Mammedov <imammedo@redhat.com> wrote:
> >
> > On Fri, 15 Oct 2021 17:25:01 +0800
> > Bin Meng <bmeng.cn@gmail.com> wrote:
> >  
> > > On Fri, Oct 15, 2021 at 4:52 PM limingwang (A) <limingwang@huawei.com> wrote:  
> > > >
> > > >
> > > > On Wed, Oct 13, 2021 at 22:41 PM Bin Meng <bin.meng@windriver.com> wrote:  
> > > > >
> > > > > On Tue, Oct 12, 2021 at 9:46 AM MingWang Li <limingwang@huawei.com> wrote:  
> > > > > >
> > > > > > From: Mingwang Li <limingwang@huawei.com>
> > > > > >
> > > > > > When I start the VM with the following command:
> > > > > > $ ./qemu-system-riscv64 -M virt,accel=kvm -m 4096M -cpu host -nographic \
> > > > > >     -name guest=riscv-guset \
> > > > > >     -smp 2 \
> > > > > >     -bios none \
> > > > > >     -kernel ./Image \
> > > > > >     -drive file=./guest.img,format=raw,id=hd0 \
> > > > > >     -device virtio-blk-device,drive=hd0 \
> > > > > >     -append "root=/dev/vda rw console=ttyS0 earlycon=sbi" \
> > > > > >     -object  
> > > > > memory-backend-file,id=mem,size=4096M,mem-path=/dev/hugepages,share=on \  
> > > > > >     -numa node,memdev=mem -mem-prealloc \
> > > > > >     -chardev socket,id=char0,path=/mnt/vhost-net0 \
> > > > > >     -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
> > > > > >     -device
> > > > > > virtio-net-pci,mac=52:54:00:00:00:01,netdev=mynet1,mrg_rxbuf=on,csum=o
> > > > > > n,guest_csum=on,guest_ecn=on \
> > > > > >
> > > > > > Then, QEMU displays the following error information:
> > > > > > qemu-system-riscv64: Failed initializing vhost-user memory map,
> > > > > > consider using -object memory-backend-file share=on  
> > > > >
> > > > > I see your command line parameters already contain "-object memory-backend-file
> > > > > share=on", so this error message is not accurate.  
> > > >
> > > > QEMU uses this command to alloc fd in the "memory_region_init_ram_from_file" function
> > > > and assigns the value of fd to mr->ram_block-fd. If the QEMU uses the default memory to
> > > > initialize the system, the QEMU cannot obtain the fd in the "vhost_user_mem_section_filter"
> > > > function when initializing the vhost-user. As a result, an error is reported in the "vhost_user_fill_set_mem_table_msg"
> > > > function.
> > > >
> > > > Because of the above bug, even if "-object memory-backend-file share=on" is added to the command line,
> > > > the QEMU still reports an error.  
> > >
> > > Yes, what I meant is that QEMU should not report such inaccurate
> > > messages because of some random codes elsewhere.
> > >
> > > With current message, it suggested user use "-object
> > > memory-backend-file share=on" in the command line, but it is already
> > > used. So this is a false alarm. The "bug" is somewhere else.  
> >
> > bug is in using memory_region_init_ram(),
> > which can't possibly handle vhost-user, and can't work as expected with
> > '-numa node,memdev' options.
> > Before main ram infrastructure was converted to memdev,
> > one should have used memory_region_allocate_system_memory() for
> > allocating main RAM, so numa usecase was broken from the start.
> > Later it old API was dropped in favor of more flexible/generic
> > MachineState::ram approach (see commits 68a86dc15ccd..f0530f14c7c35d).  
> 
> Thanks for the detailed pointers.
> 
> I wonder if it is possible to make the error message to be clearer, so
> instead of having
> 
>     "qemu-system-riscv64: Failed initializing vhost-user memory map,
> consider using -object memory-backend-file share=on"
> 
> can we do:
> 
>     "qemu-system-riscv64: Failed initializing vhost-user memory map,
> considering using MachineState::ram instead of manually initializing
> RAM memory region."
> 
> which is more straightforward?

It would only make sense in context of this thread and
give a hint to a developer how to fix bug in machine code
but won't give a clue to the end user what's wrong with
configuration.

Maybe following would be better:
 "Failed initializing vhost-user memory map, vhost requires shared system memory."
 "See 'System Emulation::Device Emulation::Emulated Devices::vhost-user back ends'
  chapter in QEMU manual."

the chapter gives an example how to correctly configure vhost-user
(albeit using old style)

 
> >
> >
> > Modulo commit message, patch looks good to me and does what
> > every machine should do. (I though that I've converted every
> > existing to generalized MachineState::ram but it looks like
> > riscv was missed).  
> 
> Indeed all riscv boards are doing the same thing.
> 
> >
> > So we can model commit message after bd457782b3b0a,
> > and also add that the patch fixes broken -numa node,memdev case,
> > which never properly worked. It also opens possibility to
> > use vhost-user/virtiosf with main RAM if main RAM is
> > provided explicitly via machine.memory-backend option
> > with shared memory backend.
> >
> > Btw: is there other riscv machines that allocate RAM directly?
> > (if yes, those should be fixed as well, a patch per machine)
> >  
> 
> I will see if I can get some patches to fix other riscv machines.
> 
> Regards,
> Bin
>

Patchew 2.1-devel-0870f84

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