* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-06-29 14:09 ` [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types Andrew Jones
@ 2020-06-29 14:18 ` Philippe Mathieu-Daudé
2020-07-02 9:48 ` Laszlo Ersek
` (2 subsequent siblings)
3 siblings, 0 replies; 25+ messages in thread
From: Philippe Mathieu-Daudé @ 2020-06-29 14:18 UTC (permalink / raw)
To: Andrew Jones, qemu-devel, qemu-arm
Cc: peter.maydell, mst, shannon.zhaosl, ard.biesheuvel, imammedo,
lersek, eric.auger
On 6/29/20 4:09 PM, Andrew Jones wrote:
> The flash device is exclusively for the host-controlled firmware, so
> we should not expose it to the OS. Exposing it risks the OS messing
> with it, which could break firmware runtime services and surprise the
> OS when all its changes disappear after reboot.
>
> As firmware needs the device and uses DT, we leave the device exposed
> there. It's up to firmware to remove the nodes from DT before sending
> it on to the OS. However, there's no need to force firmware to remove
> tables from ACPI (which it doesn't know how to do anyway), so we
> simply don't add the tables in the first place. But, as we've been
> adding the tables for quite some time and don't want to change the
> default hardware exposed to versioned machines, then we only stop
> exposing the flash device tables for 5.1 and later machine types.
>
> Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Suggested-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> hw/arm/virt-acpi-build.c | 5 ++++-
> hw/arm/virt.c | 3 +++
> include/hw/arm/virt.h | 1 +
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 1384a2cf2ab4..91f0df7b13a3 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> static void
> build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> Aml *scope, *dsdt;
> MachineState *ms = MACHINE(vms);
> const MemMapEntry *memmap = vms->memmap;
> @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> (irqmap[VIRT_UART] + ARM_SPI_BASE));
> - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + if (vmc->acpi_expose_flash) {
> + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + }
> acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index cd0834ce7faf..5adc9ff799ef 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
>
> static void virt_machine_5_0_options(MachineClass *mc)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> +
> virt_machine_5_1_options(mc);
> compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> mc->numa_mem_supported = true;
> + vmc->acpi_expose_flash = true;
> }
> DEFINE_VIRT_MACHINE(5, 0)
>
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 31878ddc7223..c65be5fe0bb6 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -119,6 +119,7 @@ typedef struct {
> bool no_highmem_ecam;
> bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
> bool kvm_no_adjvtime;
> + bool acpi_expose_flash;
> } VirtMachineClass;
>
> typedef struct {
>
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-06-29 14:09 ` [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types Andrew Jones
2020-06-29 14:18 ` Philippe Mathieu-Daudé
@ 2020-07-02 9:48 ` Laszlo Ersek
2020-07-02 9:53 ` Michael S. Tsirkin
2020-07-13 8:49 ` Igor Mammedov
3 siblings, 0 replies; 25+ messages in thread
From: Laszlo Ersek @ 2020-07-02 9:48 UTC (permalink / raw)
To: Andrew Jones, qemu-devel, qemu-arm
Cc: peter.maydell, mst, shannon.zhaosl, ard.biesheuvel, imammedo,
philmd, eric.auger
On 06/29/20 16:09, Andrew Jones wrote:
> The flash device is exclusively for the host-controlled firmware, so
> we should not expose it to the OS. Exposing it risks the OS messing
> with it, which could break firmware runtime services and surprise the
> OS when all its changes disappear after reboot.
>
> As firmware needs the device and uses DT, we leave the device exposed
> there. It's up to firmware to remove the nodes from DT before sending
> it on to the OS. However, there's no need to force firmware to remove
> tables from ACPI (which it doesn't know how to do anyway), so we
> simply don't add the tables in the first place. But, as we've been
> adding the tables for quite some time and don't want to change the
> default hardware exposed to versioned machines, then we only stop
> exposing the flash device tables for 5.1 and later machine types.
>
> Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Suggested-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
> hw/arm/virt-acpi-build.c | 5 ++++-
> hw/arm/virt.c | 3 +++
> include/hw/arm/virt.h | 1 +
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 1384a2cf2ab4..91f0df7b13a3 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> static void
> build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> Aml *scope, *dsdt;
> MachineState *ms = MACHINE(vms);
> const MemMapEntry *memmap = vms->memmap;
> @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> (irqmap[VIRT_UART] + ARM_SPI_BASE));
> - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + if (vmc->acpi_expose_flash) {
> + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + }
> acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index cd0834ce7faf..5adc9ff799ef 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
>
> static void virt_machine_5_0_options(MachineClass *mc)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> +
> virt_machine_5_1_options(mc);
> compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> mc->numa_mem_supported = true;
> + vmc->acpi_expose_flash = true;
> }
> DEFINE_VIRT_MACHINE(5, 0)
>
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 31878ddc7223..c65be5fe0bb6 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -119,6 +119,7 @@ typedef struct {
> bool no_highmem_ecam;
> bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
> bool kvm_no_adjvtime;
> + bool acpi_expose_flash;
> } VirtMachineClass;
>
> typedef struct {
>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Thank you!
Laszlo
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-06-29 14:09 ` [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types Andrew Jones
2020-06-29 14:18 ` Philippe Mathieu-Daudé
2020-07-02 9:48 ` Laszlo Ersek
@ 2020-07-02 9:53 ` Michael S. Tsirkin
2020-07-02 10:16 ` Peter Maydell
2020-07-13 8:49 ` Igor Mammedov
3 siblings, 1 reply; 25+ messages in thread
From: Michael S. Tsirkin @ 2020-07-02 9:53 UTC (permalink / raw)
To: Andrew Jones
Cc: peter.maydell, eric.auger, philmd, qemu-devel, shannon.zhaosl,
qemu-arm, ard.biesheuvel, imammedo, lersek
On Mon, Jun 29, 2020 at 04:09:37PM +0200, Andrew Jones wrote:
> The flash device is exclusively for the host-controlled firmware, so
> we should not expose it to the OS. Exposing it risks the OS messing
> with it, which could break firmware runtime services and surprise the
> OS when all its changes disappear after reboot.
>
> As firmware needs the device and uses DT, we leave the device exposed
> there. It's up to firmware to remove the nodes from DT before sending
> it on to the OS. However, there's no need to force firmware to remove
> tables from ACPI (which it doesn't know how to do anyway), so we
> simply don't add the tables in the first place. But, as we've been
> adding the tables for quite some time and don't want to change the
> default hardware exposed to versioned machines, then we only stop
> exposing the flash device tables for 5.1 and later machine types.
>
> Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Suggested-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
So who's merging this? Mostly ACPI things so I guess my tree?
If so can I get acks from ARM maintainers pls?
Thanks!
> ---
> hw/arm/virt-acpi-build.c | 5 ++++-
> hw/arm/virt.c | 3 +++
> include/hw/arm/virt.h | 1 +
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 1384a2cf2ab4..91f0df7b13a3 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> static void
> build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> Aml *scope, *dsdt;
> MachineState *ms = MACHINE(vms);
> const MemMapEntry *memmap = vms->memmap;
> @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> (irqmap[VIRT_UART] + ARM_SPI_BASE));
> - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + if (vmc->acpi_expose_flash) {
> + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + }
> acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index cd0834ce7faf..5adc9ff799ef 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
>
> static void virt_machine_5_0_options(MachineClass *mc)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> +
> virt_machine_5_1_options(mc);
> compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> mc->numa_mem_supported = true;
> + vmc->acpi_expose_flash = true;
> }
> DEFINE_VIRT_MACHINE(5, 0)
>
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 31878ddc7223..c65be5fe0bb6 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -119,6 +119,7 @@ typedef struct {
> bool no_highmem_ecam;
> bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
> bool kvm_no_adjvtime;
> + bool acpi_expose_flash;
> } VirtMachineClass;
>
> typedef struct {
> --
> 2.25.4
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-02 9:53 ` Michael S. Tsirkin
@ 2020-07-02 10:16 ` Peter Maydell
2020-07-02 11:13 ` Michael S. Tsirkin
0 siblings, 1 reply; 25+ messages in thread
From: Peter Maydell @ 2020-07-02 10:16 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Andrew Jones, Eric Auger, Philippe Mathieu-Daudé,
QEMU Developers, Shannon Zhao, qemu-arm, ard.biesheuvel,
Igor Mammedov, Laszlo Ersek
On Thu, 2 Jul 2020 at 10:53, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Jun 29, 2020 at 04:09:37PM +0200, Andrew Jones wrote:
> > The flash device is exclusively for the host-controlled firmware, so
> > we should not expose it to the OS. Exposing it risks the OS messing
> > with it, which could break firmware runtime services and surprise the
> > OS when all its changes disappear after reboot.
> >
> > As firmware needs the device and uses DT, we leave the device exposed
> > there. It's up to firmware to remove the nodes from DT before sending
> > it on to the OS. However, there's no need to force firmware to remove
> > tables from ACPI (which it doesn't know how to do anyway), so we
> > simply don't add the tables in the first place. But, as we've been
> > adding the tables for quite some time and don't want to change the
> > default hardware exposed to versioned machines, then we only stop
> > exposing the flash device tables for 5.1 and later machine types.
> >
> > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
>
> So who's merging this? Mostly ACPI things so I guess my tree?
> If so can I get acks from ARM maintainers pls?
This is on my to-look-at queue but in theory I'm on holiday this week :-)
-- PMM
^ permalink raw reply [flat|nested] 25+ messages in thread
* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-02 10:16 ` Peter Maydell
@ 2020-07-02 11:13 ` Michael S. Tsirkin
0 siblings, 0 replies; 25+ messages in thread
From: Michael S. Tsirkin @ 2020-07-02 11:13 UTC (permalink / raw)
To: Peter Maydell
Cc: Andrew Jones, Eric Auger, Philippe Mathieu-Daudé,
QEMU Developers, Shannon Zhao, qemu-arm, ard.biesheuvel,
Igor Mammedov, Laszlo Ersek
On Thu, Jul 02, 2020 at 11:16:03AM +0100, Peter Maydell wrote:
> On Thu, 2 Jul 2020 at 10:53, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Mon, Jun 29, 2020 at 04:09:37PM +0200, Andrew Jones wrote:
> > > The flash device is exclusively for the host-controlled firmware, so
> > > we should not expose it to the OS. Exposing it risks the OS messing
> > > with it, which could break firmware runtime services and surprise the
> > > OS when all its changes disappear after reboot.
> > >
> > > As firmware needs the device and uses DT, we leave the device exposed
> > > there. It's up to firmware to remove the nodes from DT before sending
> > > it on to the OS. However, there's no need to force firmware to remove
> > > tables from ACPI (which it doesn't know how to do anyway), so we
> > > simply don't add the tables in the first place. But, as we've been
> > > adding the tables for quite some time and don't want to change the
> > > default hardware exposed to versioned machines, then we only stop
> > > exposing the flash device tables for 5.1 and later machine types.
> > >
> > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> >
> > So who's merging this? Mostly ACPI things so I guess my tree?
> > If so can I get acks from ARM maintainers pls?
>
> This is on my to-look-at queue but in theory I'm on holiday this week :-)
>
> -- PMM
I picked up patch 1 for now :)
--
MST
^ permalink raw reply [flat|nested] 25+ messages in thread
* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-06-29 14:09 ` [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types Andrew Jones
` (2 preceding siblings ...)
2020-07-02 9:53 ` Michael S. Tsirkin
@ 2020-07-13 8:49 ` Igor Mammedov
2020-07-14 5:51 ` Andrew Jones
3 siblings, 1 reply; 25+ messages in thread
From: Igor Mammedov @ 2020-07-13 8:49 UTC (permalink / raw)
To: Andrew Jones
Cc: peter.maydell, mst, philmd, qemu-devel, shannon.zhaosl, qemu-arm,
ard.biesheuvel, lersek, eric.auger
On Mon, 29 Jun 2020 16:09:37 +0200
Andrew Jones <drjones@redhat.com> wrote:
> The flash device is exclusively for the host-controlled firmware, so
> we should not expose it to the OS. Exposing it risks the OS messing
> with it, which could break firmware runtime services and surprise the
> OS when all its changes disappear after reboot.
>
> As firmware needs the device and uses DT, we leave the device exposed
> there. It's up to firmware to remove the nodes from DT before sending
> it on to the OS. However, there's no need to force firmware to remove
> tables from ACPI (which it doesn't know how to do anyway), so we
> simply don't add the tables in the first place. But, as we've been
> adding the tables for quite some time and don't want to change the
> default hardware exposed to versioned machines, then we only stop
> exposing the flash device tables for 5.1 and later machine types.
>
> Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Suggested-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
> hw/arm/virt-acpi-build.c | 5 ++++-
> hw/arm/virt.c | 3 +++
> include/hw/arm/virt.h | 1 +
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 1384a2cf2ab4..91f0df7b13a3 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> static void
> build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> Aml *scope, *dsdt;
> MachineState *ms = MACHINE(vms);
> const MemMapEntry *memmap = vms->memmap;
> @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> (irqmap[VIRT_UART] + ARM_SPI_BASE));
> - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + if (vmc->acpi_expose_flash) {
> + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> + }
> acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index cd0834ce7faf..5adc9ff799ef 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
>
> static void virt_machine_5_0_options(MachineClass *mc)
> {
> + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> +
> virt_machine_5_1_options(mc);
> compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> mc->numa_mem_supported = true;
> + vmc->acpi_expose_flash = true;
we usually do not version ACPI tables changes
(unless we have a good reason to do so)
> }
> DEFINE_VIRT_MACHINE(5, 0)
>
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 31878ddc7223..c65be5fe0bb6 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -119,6 +119,7 @@ typedef struct {
> bool no_highmem_ecam;
> bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
> bool kvm_no_adjvtime;
> + bool acpi_expose_flash;
> } VirtMachineClass;
>
> typedef struct {
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-13 8:49 ` Igor Mammedov
@ 2020-07-14 5:51 ` Andrew Jones
2020-07-14 8:57 ` Michael S. Tsirkin
0 siblings, 1 reply; 25+ messages in thread
From: Andrew Jones @ 2020-07-14 5:51 UTC (permalink / raw)
To: Igor Mammedov
Cc: peter.maydell, mst, lersek, qemu-devel, shannon.zhaosl, qemu-arm,
ard.biesheuvel, philmd, eric.auger
On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote:
> On Mon, 29 Jun 2020 16:09:37 +0200
> Andrew Jones <drjones@redhat.com> wrote:
>
> > The flash device is exclusively for the host-controlled firmware, so
> > we should not expose it to the OS. Exposing it risks the OS messing
> > with it, which could break firmware runtime services and surprise the
> > OS when all its changes disappear after reboot.
> >
> > As firmware needs the device and uses DT, we leave the device exposed
> > there. It's up to firmware to remove the nodes from DT before sending
> > it on to the OS. However, there's no need to force firmware to remove
> > tables from ACPI (which it doesn't know how to do anyway), so we
> > simply don't add the tables in the first place. But, as we've been
> > adding the tables for quite some time and don't want to change the
> > default hardware exposed to versioned machines, then we only stop
> > exposing the flash device tables for 5.1 and later machine types.
> >
> > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > ---
> > hw/arm/virt-acpi-build.c | 5 ++++-
> > hw/arm/virt.c | 3 +++
> > include/hw/arm/virt.h | 1 +
> > 3 files changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > index 1384a2cf2ab4..91f0df7b13a3 100644
> > --- a/hw/arm/virt-acpi-build.c
> > +++ b/hw/arm/virt-acpi-build.c
> > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> > static void
> > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > {
> > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> > Aml *scope, *dsdt;
> > MachineState *ms = MACHINE(vms);
> > const MemMapEntry *memmap = vms->memmap;
> > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> > (irqmap[VIRT_UART] + ARM_SPI_BASE));
> > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > + if (vmc->acpi_expose_flash) {
> > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > + }
> > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index cd0834ce7faf..5adc9ff799ef 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
> >
> > static void virt_machine_5_0_options(MachineClass *mc)
> > {
> > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> > +
> > virt_machine_5_1_options(mc);
> > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> > mc->numa_mem_supported = true;
> > + vmc->acpi_expose_flash = true;
>
> we usually do not version ACPI tables changes
> (unless we have a good reason to do so)
Even when the change is to remove the exposure of hardware from the guest?
Before this change, if a guest looked, it had a flash, after this change,
if a guest looks, it doesn't. I'd feel much better versioning a change
like that, than not.
Thanks,
drew
>
> > }
> > DEFINE_VIRT_MACHINE(5, 0)
> >
> > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> > index 31878ddc7223..c65be5fe0bb6 100644
> > --- a/include/hw/arm/virt.h
> > +++ b/include/hw/arm/virt.h
> > @@ -119,6 +119,7 @@ typedef struct {
> > bool no_highmem_ecam;
> > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
> > bool kvm_no_adjvtime;
> > + bool acpi_expose_flash;
> > } VirtMachineClass;
> >
> > typedef struct {
>
>
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-14 5:51 ` Andrew Jones
@ 2020-07-14 8:57 ` Michael S. Tsirkin
2020-07-14 9:23 ` Andrew Jones
0 siblings, 1 reply; 25+ messages in thread
From: Michael S. Tsirkin @ 2020-07-14 8:57 UTC (permalink / raw)
To: Andrew Jones
Cc: peter.maydell, eric.auger, lersek, qemu-devel, shannon.zhaosl,
qemu-arm, ard.biesheuvel, Igor Mammedov, philmd
On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote:
> On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote:
> > On Mon, 29 Jun 2020 16:09:37 +0200
> > Andrew Jones <drjones@redhat.com> wrote:
> >
> > > The flash device is exclusively for the host-controlled firmware, so
> > > we should not expose it to the OS. Exposing it risks the OS messing
> > > with it, which could break firmware runtime services and surprise the
> > > OS when all its changes disappear after reboot.
> > >
> > > As firmware needs the device and uses DT, we leave the device exposed
> > > there. It's up to firmware to remove the nodes from DT before sending
> > > it on to the OS. However, there's no need to force firmware to remove
> > > tables from ACPI (which it doesn't know how to do anyway), so we
> > > simply don't add the tables in the first place. But, as we've been
> > > adding the tables for quite some time and don't want to change the
> > > default hardware exposed to versioned machines, then we only stop
> > > exposing the flash device tables for 5.1 and later machine types.
> > >
> > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > ---
> > > hw/arm/virt-acpi-build.c | 5 ++++-
> > > hw/arm/virt.c | 3 +++
> > > include/hw/arm/virt.h | 1 +
> > > 3 files changed, 8 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > > index 1384a2cf2ab4..91f0df7b13a3 100644
> > > --- a/hw/arm/virt-acpi-build.c
> > > +++ b/hw/arm/virt-acpi-build.c
> > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> > > static void
> > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > {
> > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> > > Aml *scope, *dsdt;
> > > MachineState *ms = MACHINE(vms);
> > > const MemMapEntry *memmap = vms->memmap;
> > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> > > (irqmap[VIRT_UART] + ARM_SPI_BASE));
> > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > + if (vmc->acpi_expose_flash) {
> > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > + }
> > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > > index cd0834ce7faf..5adc9ff799ef 100644
> > > --- a/hw/arm/virt.c
> > > +++ b/hw/arm/virt.c
> > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
> > >
> > > static void virt_machine_5_0_options(MachineClass *mc)
> > > {
> > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> > > +
> > > virt_machine_5_1_options(mc);
> > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> > > mc->numa_mem_supported = true;
> > > + vmc->acpi_expose_flash = true;
> >
> > we usually do not version ACPI tables changes
> > (unless we have a good reason to do so)
>
> Even when the change is to remove the exposure of hardware from the guest?
> Before this change, if a guest looked, it had a flash, after this change,
> if a guest looks, it doesn't.
It's up to the relevant maintainers who know what the semantics are.
FYI ACPI tables only change across a reset though.
So it's a question of whether guests get confused even if this
changes after a reboot.
Versioning is generally safer, but it's a good idea to document
the motivation for it.
> I'd feel much better versioning a change
> like that, than not.
>
> Thanks,
> drew
>
> >
> > > }
> > > DEFINE_VIRT_MACHINE(5, 0)
> > >
> > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> > > index 31878ddc7223..c65be5fe0bb6 100644
> > > --- a/include/hw/arm/virt.h
> > > +++ b/include/hw/arm/virt.h
> > > @@ -119,6 +119,7 @@ typedef struct {
> > > bool no_highmem_ecam;
> > > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */
> > > bool kvm_no_adjvtime;
> > > + bool acpi_expose_flash;
> > > } VirtMachineClass;
> > >
> > > typedef struct {
> >
> >
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-14 8:57 ` Michael S. Tsirkin
@ 2020-07-14 9:23 ` Andrew Jones
2020-07-14 9:31 ` Michael S. Tsirkin
2020-07-14 14:41 ` Igor Mammedov
0 siblings, 2 replies; 25+ messages in thread
From: Andrew Jones @ 2020-07-14 9:23 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: peter.maydell, eric.auger, philmd, qemu-devel, shannon.zhaosl,
qemu-arm, ard.biesheuvel, Igor Mammedov, lersek
On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote:
> On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote:
> > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote:
> > > On Mon, 29 Jun 2020 16:09:37 +0200
> > > Andrew Jones <drjones@redhat.com> wrote:
> > >
> > > > The flash device is exclusively for the host-controlled firmware, so
> > > > we should not expose it to the OS. Exposing it risks the OS messing
> > > > with it, which could break firmware runtime services and surprise the
> > > > OS when all its changes disappear after reboot.
> > > >
> > > > As firmware needs the device and uses DT, we leave the device exposed
> > > > there. It's up to firmware to remove the nodes from DT before sending
> > > > it on to the OS. However, there's no need to force firmware to remove
> > > > tables from ACPI (which it doesn't know how to do anyway), so we
> > > > simply don't add the tables in the first place. But, as we've been
> > > > adding the tables for quite some time and don't want to change the
> > > > default hardware exposed to versioned machines, then we only stop
> > > > exposing the flash device tables for 5.1 and later machine types.
> > > >
> > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > > > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > > ---
> > > > hw/arm/virt-acpi-build.c | 5 ++++-
> > > > hw/arm/virt.c | 3 +++
> > > > include/hw/arm/virt.h | 1 +
> > > > 3 files changed, 8 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > > > index 1384a2cf2ab4..91f0df7b13a3 100644
> > > > --- a/hw/arm/virt-acpi-build.c
> > > > +++ b/hw/arm/virt-acpi-build.c
> > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> > > > static void
> > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > {
> > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> > > > Aml *scope, *dsdt;
> > > > MachineState *ms = MACHINE(vms);
> > > > const MemMapEntry *memmap = vms->memmap;
> > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> > > > (irqmap[VIRT_UART] + ARM_SPI_BASE));
> > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > + if (vmc->acpi_expose_flash) {
> > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > + }
> > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > > > index cd0834ce7faf..5adc9ff799ef 100644
> > > > --- a/hw/arm/virt.c
> > > > +++ b/hw/arm/virt.c
> > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
> > > >
> > > > static void virt_machine_5_0_options(MachineClass *mc)
> > > > {
> > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> > > > +
> > > > virt_machine_5_1_options(mc);
> > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> > > > mc->numa_mem_supported = true;
> > > > + vmc->acpi_expose_flash = true;
> > >
> > > we usually do not version ACPI tables changes
> > > (unless we have a good reason to do so)
> >
> > Even when the change is to remove the exposure of hardware from the guest?
> > Before this change, if a guest looked, it had a flash, after this change,
> > if a guest looks, it doesn't.
>
> It's up to the relevant maintainers who know what the semantics are.
> FYI ACPI tables only change across a reset though.
> So it's a question of whether guests get confused even if this
> changes after a reboot.
Yup, but it's still the same "machine", so a user may wonder why it
changed.
> Versioning is generally safer, but it's a good idea to document
> the motivation for it.
>
Well, in this case, we could probably push this change to old machine
types and nobody would notice. If a guest is using ACPI, then it must
be using firmware, and if they're using firmware, then they can't be
using the flash. So the user shouldn't care if it's there or not. The
only justification for the versioning is because "it's safer". If
people feel strongly about avoiding versioning when it's not obviously
necessary, then I can respin without it.
Thanks,
drew
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-14 9:23 ` Andrew Jones
@ 2020-07-14 9:31 ` Michael S. Tsirkin
2020-07-14 14:41 ` Igor Mammedov
1 sibling, 0 replies; 25+ messages in thread
From: Michael S. Tsirkin @ 2020-07-14 9:31 UTC (permalink / raw)
To: Andrew Jones
Cc: peter.maydell, eric.auger, philmd, qemu-devel, shannon.zhaosl,
qemu-arm, ard.biesheuvel, Igor Mammedov, lersek
On Tue, Jul 14, 2020 at 11:23:25AM +0200, Andrew Jones wrote:
> On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote:
> > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote:
> > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote:
> > > > On Mon, 29 Jun 2020 16:09:37 +0200
> > > > Andrew Jones <drjones@redhat.com> wrote:
> > > >
> > > > > The flash device is exclusively for the host-controlled firmware, so
> > > > > we should not expose it to the OS. Exposing it risks the OS messing
> > > > > with it, which could break firmware runtime services and surprise the
> > > > > OS when all its changes disappear after reboot.
> > > > >
> > > > > As firmware needs the device and uses DT, we leave the device exposed
> > > > > there. It's up to firmware to remove the nodes from DT before sending
> > > > > it on to the OS. However, there's no need to force firmware to remove
> > > > > tables from ACPI (which it doesn't know how to do anyway), so we
> > > > > simply don't add the tables in the first place. But, as we've been
> > > > > adding the tables for quite some time and don't want to change the
> > > > > default hardware exposed to versioned machines, then we only stop
> > > > > exposing the flash device tables for 5.1 and later machine types.
> > > > >
> > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > > > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > > > ---
> > > > > hw/arm/virt-acpi-build.c | 5 ++++-
> > > > > hw/arm/virt.c | 3 +++
> > > > > include/hw/arm/virt.h | 1 +
> > > > > 3 files changed, 8 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > > > > index 1384a2cf2ab4..91f0df7b13a3 100644
> > > > > --- a/hw/arm/virt-acpi-build.c
> > > > > +++ b/hw/arm/virt-acpi-build.c
> > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> > > > > static void
> > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > > {
> > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> > > > > Aml *scope, *dsdt;
> > > > > MachineState *ms = MACHINE(vms);
> > > > > const MemMapEntry *memmap = vms->memmap;
> > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE));
> > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > > + if (vmc->acpi_expose_flash) {
> > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > > + }
> > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > > > > index cd0834ce7faf..5adc9ff799ef 100644
> > > > > --- a/hw/arm/virt.c
> > > > > +++ b/hw/arm/virt.c
> > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
> > > > >
> > > > > static void virt_machine_5_0_options(MachineClass *mc)
> > > > > {
> > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> > > > > +
> > > > > virt_machine_5_1_options(mc);
> > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> > > > > mc->numa_mem_supported = true;
> > > > > + vmc->acpi_expose_flash = true;
> > > >
> > > > we usually do not version ACPI tables changes
> > > > (unless we have a good reason to do so)
> > >
> > > Even when the change is to remove the exposure of hardware from the guest?
> > > Before this change, if a guest looked, it had a flash, after this change,
> > > if a guest looks, it doesn't.
> >
> > It's up to the relevant maintainers who know what the semantics are.
> > FYI ACPI tables only change across a reset though.
> > So it's a question of whether guests get confused even if this
> > changes after a reboot.
>
> Yup, but it's still the same "machine", so a user may wonder why it
> changed.
>
> > Versioning is generally safer, but it's a good idea to document
> > the motivation for it.
> >
>
> Well, in this case, we could probably push this change to old machine
> types and nobody would notice. If a guest is using ACPI, then it must
> be using firmware, and if they're using firmware, then they can't be
> using the flash. So the user shouldn't care if it's there or not. The
> only justification for the versioning is because "it's safer". If
> people feel strongly about avoiding versioning when it's not obviously
> necessary, then I can respin without it.
>
> Thanks,
> drew
It's up to maintainers either way, but please do tweak the motivation in the commit log
to include the above.
--
MST
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-14 9:23 ` Andrew Jones
2020-07-14 9:31 ` Michael S. Tsirkin
@ 2020-07-14 14:41 ` Igor Mammedov
2020-07-15 6:36 ` Andrew Jones
1 sibling, 1 reply; 25+ messages in thread
From: Igor Mammedov @ 2020-07-14 14:41 UTC (permalink / raw)
To: Andrew Jones
Cc: peter.maydell, eric.auger, lersek, Michael S. Tsirkin,
qemu-devel, shannon.zhaosl, qemu-arm, ard.biesheuvel, philmd
On Tue, 14 Jul 2020 11:23:25 +0200
Andrew Jones <drjones@redhat.com> wrote:
> On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote:
> > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote:
> > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote:
> > > > On Mon, 29 Jun 2020 16:09:37 +0200
> > > > Andrew Jones <drjones@redhat.com> wrote:
> > > >
> > > > > The flash device is exclusively for the host-controlled firmware, so
> > > > > we should not expose it to the OS. Exposing it risks the OS messing
> > > > > with it, which could break firmware runtime services and surprise the
> > > > > OS when all its changes disappear after reboot.
> > > > >
> > > > > As firmware needs the device and uses DT, we leave the device exposed
> > > > > there. It's up to firmware to remove the nodes from DT before sending
> > > > > it on to the OS. However, there's no need to force firmware to remove
> > > > > tables from ACPI (which it doesn't know how to do anyway), so we
> > > > > simply don't add the tables in the first place. But, as we've been
> > > > > adding the tables for quite some time and don't want to change the
> > > > > default hardware exposed to versioned machines, then we only stop
> > > > > exposing the flash device tables for 5.1 and later machine types.
> > > > >
> > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > > > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > > > ---
> > > > > hw/arm/virt-acpi-build.c | 5 ++++-
> > > > > hw/arm/virt.c | 3 +++
> > > > > include/hw/arm/virt.h | 1 +
> > > > > 3 files changed, 8 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > > > > index 1384a2cf2ab4..91f0df7b13a3 100644
> > > > > --- a/hw/arm/virt-acpi-build.c
> > > > > +++ b/hw/arm/virt-acpi-build.c
> > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> > > > > static void
> > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > > {
> > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> > > > > Aml *scope, *dsdt;
> > > > > MachineState *ms = MACHINE(vms);
> > > > > const MemMapEntry *memmap = vms->memmap;
> > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE));
> > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > > + if (vmc->acpi_expose_flash) {
> > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > > + }
> > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > > > > index cd0834ce7faf..5adc9ff799ef 100644
> > > > > --- a/hw/arm/virt.c
> > > > > +++ b/hw/arm/virt.c
> > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
> > > > >
> > > > > static void virt_machine_5_0_options(MachineClass *mc)
> > > > > {
> > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> > > > > +
> > > > > virt_machine_5_1_options(mc);
> > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> > > > > mc->numa_mem_supported = true;
> > > > > + vmc->acpi_expose_flash = true;
> > > >
> > > > we usually do not version ACPI tables changes
> > > > (unless we have a good reason to do so)
> > >
> > > Even when the change is to remove the exposure of hardware from the guest?
> > > Before this change, if a guest looked, it had a flash, after this change,
> > > if a guest looks, it doesn't.
> >
> > It's up to the relevant maintainers who know what the semantics are.
> > FYI ACPI tables only change across a reset though.
> > So it's a question of whether guests get confused even if this
> > changes after a reboot.
>
> Yup, but it's still the same "machine", so a user may wonder why it
> changed.
you can have a different firmware with the same machine type either
and it might look differently to guest OS but don't bother versioning
FW. APCI tables are also part of FW (but generated by QEMU), so the same
usually rule applies.
> > Versioning is generally safer, but it's a good idea to document
> > the motivation for it.
> >
>
> Well, in this case, we could probably push this change to old machine
> types and nobody would notice. If a guest is using ACPI, then it must
> be using firmware, and if they're using firmware, then they can't be
> using the flash. So the user shouldn't care if it's there or not. The
> only justification for the versioning is because "it's safer". If
> people feel strongly about avoiding versioning when it's not obviously
> necessary, then I can respin without it.
From my pov if it doesn't break anything don't version it, since versioning
adds complexity which cost time during review, so it would be nicer to reviewers
and to future yourself if you can help to keep it as simple as possible.
In this particular case I'd drop versioning.
> Thanks,
> drew
>
>
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-14 14:41 ` Igor Mammedov
@ 2020-07-15 6:36 ` Andrew Jones
2020-07-15 9:37 ` Andrew Jones
2020-07-15 12:26 ` Laszlo Ersek
0 siblings, 2 replies; 25+ messages in thread
From: Andrew Jones @ 2020-07-15 6:36 UTC (permalink / raw)
To: Igor Mammedov
Cc: peter.maydell, ard.biesheuvel, Michael S. Tsirkin, philmd,
qemu-devel, shannon.zhaosl, qemu-arm, eric.auger, lersek
On Tue, Jul 14, 2020 at 04:41:41PM +0200, Igor Mammedov wrote:
> On Tue, 14 Jul 2020 11:23:25 +0200
> Andrew Jones <drjones@redhat.com> wrote:
>
> > On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote:
> > > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote:
> > > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote:
> > > > > On Mon, 29 Jun 2020 16:09:37 +0200
> > > > > Andrew Jones <drjones@redhat.com> wrote:
> > > > >
> > > > > > The flash device is exclusively for the host-controlled firmware, so
> > > > > > we should not expose it to the OS. Exposing it risks the OS messing
> > > > > > with it, which could break firmware runtime services and surprise the
> > > > > > OS when all its changes disappear after reboot.
> > > > > >
> > > > > > As firmware needs the device and uses DT, we leave the device exposed
> > > > > > there. It's up to firmware to remove the nodes from DT before sending
> > > > > > it on to the OS. However, there's no need to force firmware to remove
> > > > > > tables from ACPI (which it doesn't know how to do anyway), so we
> > > > > > simply don't add the tables in the first place. But, as we've been
> > > > > > adding the tables for quite some time and don't want to change the
> > > > > > default hardware exposed to versioned machines, then we only stop
> > > > > > exposing the flash device tables for 5.1 and later machine types.
> > > > > >
> > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > > > > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > > > > ---
> > > > > > hw/arm/virt-acpi-build.c | 5 ++++-
> > > > > > hw/arm/virt.c | 3 +++
> > > > > > include/hw/arm/virt.h | 1 +
> > > > > > 3 files changed, 8 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> > > > > > index 1384a2cf2ab4..91f0df7b13a3 100644
> > > > > > --- a/hw/arm/virt-acpi-build.c
> > > > > > +++ b/hw/arm/virt-acpi-build.c
> > > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker,
> > > > > > static void
> > > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > > > {
> > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> > > > > > Aml *scope, *dsdt;
> > > > > > MachineState *ms = MACHINE(vms);
> > > > > > const MemMapEntry *memmap = vms->memmap;
> > > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
> > > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus);
> > > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
> > > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE));
> > > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > > > + if (vmc->acpi_expose_flash) {
> > > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
> > > > > > + }
> > > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
> > > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
> > > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> > > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > > > > > index cd0834ce7faf..5adc9ff799ef 100644
> > > > > > --- a/hw/arm/virt.c
> > > > > > +++ b/hw/arm/virt.c
> > > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1)
> > > > > >
> > > > > > static void virt_machine_5_0_options(MachineClass *mc)
> > > > > > {
> > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
> > > > > > +
> > > > > > virt_machine_5_1_options(mc);
> > > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len);
> > > > > > mc->numa_mem_supported = true;
> > > > > > + vmc->acpi_expose_flash = true;
> > > > >
> > > > > we usually do not version ACPI tables changes
> > > > > (unless we have a good reason to do so)
> > > >
> > > > Even when the change is to remove the exposure of hardware from the guest?
> > > > Before this change, if a guest looked, it had a flash, after this change,
> > > > if a guest looks, it doesn't.
> > >
> > > It's up to the relevant maintainers who know what the semantics are.
> > > FYI ACPI tables only change across a reset though.
> > > So it's a question of whether guests get confused even if this
> > > changes after a reboot.
> >
> > Yup, but it's still the same "machine", so a user may wonder why it
> > changed.
>
> you can have a different firmware with the same machine type either
> and it might look differently to guest OS but don't bother versioning
> FW. APCI tables are also part of FW (but generated by QEMU), so the same
> usually rule applies.
That makes sense. However, while users of real machines agree to update
their firmware after determining what will change, or at least expect
there could be a change that they'll need to adapt to, users of virtual
machines simply reboot, getting new firmware and ACPI tables, and then
possibly new surprises. Indeed, they may have opted to use a virtual
machine precisely so they could keep the environment stable across
updates of the real machine. IOW, since we can maintain a versioned
machine, then maybe we should?
>
> > > Versioning is generally safer, but it's a good idea to document
> > > the motivation for it.
> > >
> >
> > Well, in this case, we could probably push this change to old machine
> > types and nobody would notice. If a guest is using ACPI, then it must
> > be using firmware, and if they're using firmware, then they can't be
> > using the flash. So the user shouldn't care if it's there or not. The
> > only justification for the versioning is because "it's safer". If
> > people feel strongly about avoiding versioning when it's not obviously
> > necessary, then I can respin without it.
>
> From my pov if it doesn't break anything don't version it,
I don't see how we can be sure that we won't break anything. Although,
in this case, we *probably* won't.
> since versioning
> adds complexity which cost time during review, so it would be nicer to reviewers
> and to future yourself if you can help to keep it as simple as possible.
I agree with all of that.
>
> In this particular case I'd drop versioning.
>
So it sounds to me like we have some flexibility in our versioned machine
maintenance. We can choose to forgo the usual compat code when the risk is
deemed low enough. And, if somebody screams, we can always fix it later.
I can live with that. I'll go ahead and respin without the versioning.
Thanks,
drew
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-15 6:36 ` Andrew Jones
@ 2020-07-15 9:37 ` Andrew Jones
2020-07-15 12:26 ` Laszlo Ersek
1 sibling, 0 replies; 25+ messages in thread
From: Andrew Jones @ 2020-07-15 9:37 UTC (permalink / raw)
To: Igor Mammedov
Cc: peter.maydell, Michael S. Tsirkin, lersek, qemu-devel,
shannon.zhaosl, qemu-arm, ard.biesheuvel, philmd, eric.auger
On Wed, Jul 15, 2020 at 08:36:48AM +0200, Andrew Jones wrote:
> On Tue, Jul 14, 2020 at 04:41:41PM +0200, Igor Mammedov wrote:
> >
> > In this particular case I'd drop versioning.
> >
>
> So it sounds to me like we have some flexibility in our versioned machine
> maintenance. We can choose to forgo the usual compat code when the risk is
> deemed low enough. And, if somebody screams, we can always fix it later.
> I can live with that. I'll go ahead and respin without the versioning.
>
Actually this patch was already merged
2c1fb4d5c011 hw/arm/virt-acpi-build: Only expose flash on older machine types
and I don't see much value in posting a patch to remove the compat code.
Regarding the result of this discussion, my take is that unless the
policy is to always or to never use versioning, then I think we should
have guidelines documented which we can follow. Would one of the ACPI
maintainers like to submit a document with the reasoning for when and
when not to use versioning? And also for what's expected of the
commit message justification when versioning is necessary?
Thanks,
drew
^ permalink raw reply [flat|nested] 25+ messages in thread
* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-15 6:36 ` Andrew Jones
2020-07-15 9:37 ` Andrew Jones
@ 2020-07-15 12:26 ` Laszlo Ersek
2020-07-15 13:05 ` Andrew Jones
1 sibling, 1 reply; 25+ messages in thread
From: Laszlo Ersek @ 2020-07-15 12:26 UTC (permalink / raw)
To: Andrew Jones, Igor Mammedov
Cc: peter.maydell, ard.biesheuvel, Michael S. Tsirkin, qemu-devel,
shannon.zhaosl, qemu-arm, eric.auger, philmd
Hi Drew,
On 07/15/20 08:36, Andrew Jones wrote:
> So it sounds to me like we have some flexibility in our versioned machine
> maintenance. We can choose to forgo the usual compat code when the risk is
> deemed low enough. And, if somebody screams, we can always fix it later.
> I can live with that. I'll go ahead and respin without the versioning.
In that case, please don't simply remove the acpi_dsdt_add_flash() call
from build_dsdt(), because then "git blame" won't be able to help later.
Can you please replace the call with a comment instead, similar to the
RTC comment from commit 67736a25f865 ("ARM: virt: Don't generate RTC
ACPI device when using UEFI", 2016-01-15)?
Thanks!
Laszlo
^ permalink raw reply [flat|nested] 25+ messages in thread* Re: [PATCH 3/4] hw/arm/virt-acpi-build: Only expose flash on older machine types
2020-07-15 12:26 ` Laszlo Ersek
@ 2020-07-15 13:05 ` Andrew Jones
0 siblings, 0 replies; 25+ messages in thread
From: Andrew Jones @ 2020-07-15 13:05 UTC (permalink / raw)
To: Laszlo Ersek
Cc: peter.maydell, ard.biesheuvel, Michael S. Tsirkin, qemu-devel,
shannon.zhaosl, qemu-arm, eric.auger, Igor Mammedov, philmd
On Wed, Jul 15, 2020 at 02:26:19PM +0200, Laszlo Ersek wrote:
> Hi Drew,
>
> On 07/15/20 08:36, Andrew Jones wrote:
>
> > So it sounds to me like we have some flexibility in our versioned machine
> > maintenance. We can choose to forgo the usual compat code when the risk is
> > deemed low enough. And, if somebody screams, we can always fix it later.
> > I can live with that. I'll go ahead and respin without the versioning.
>
> In that case, please don't simply remove the acpi_dsdt_add_flash() call
> from build_dsdt(), because then "git blame" won't be able to help later.
> Can you please replace the call with a comment instead, similar to the
> RTC comment from commit 67736a25f865 ("ARM: virt: Don't generate RTC
> ACPI device when using UEFI", 2016-01-15)?
>
In the end I won't be respinning, as this patch is already merged. And,
unless Igor twists my arm, then I don't plan to write another patch
that removes the compat code. If I did remove it, I'd put a comment
in there for git-blame to find. And, in the comment I'd write "Igor
said to remove this", because git-blame would otherwise blame me :-)
Thanks,
drew
^ permalink raw reply [flat|nested] 25+ messages in thread