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[PULL 6/7] hw/loongarch: virt: pass random seed to fdt

Song Gao posted 7 patches 2 months, 1 week ago
There is a newer version of this series
[PULL 6/7] hw/loongarch: virt: pass random seed to fdt
Posted by Song Gao 2 months, 1 week ago 
From: "Jason A. Donenfeld" <Jason@zx2c4.com>

If the FDT contains /chosen/rng-seed, then the Linux RNG will use it to
initialize early. Set this using the usual guest random number
generation function.

This is the same procedure that's done in b91b6b5a2c ("hw/microblaze:
pass random seed to fdt"), e4b4f0b71c ("hw/riscv: virt: pass random seed
to fdt"), c6fe3e6b4c ("hw/openrisc: virt: pass random seed to fdt"),
67f7e426e5 ("hw/i386: pass RNG seed via setup_data entry"), c287941a4d
("hw/rx: pass random seed to fdt"), 5e19cc68fb ("hw/mips: boston: pass
random seed to fdt"), 6b23a67916 ("hw/nios2: virt: pass random seed to fdt")
c4b075318e ("hw/ppc: pass random seed to fdt"), and 5242876f37
("hw/arm/virt: dt: add rng-seed property").

These earlier commits later were amended to rerandomize the RNG seed on
snapshot load, but the LoongArch code somehow already does that, despite
not having this patch here, presumably due to some lucky copy and
pasting.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240905153316.2038769-1-Jason@zx2c4.com>
Signed-off-by: Song Gao <gaosong@loongson.cn>
---
 hw/loongarch/virt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
index 76dd29a391..81b1f9486f 100644
--- a/hw/loongarch/virt.c
+++ b/hw/loongarch/virt.c
@@ -48,6 +48,7 @@
 #include "hw/block/flash.h"
 #include "hw/virtio/virtio-iommu.h"
 #include "qemu/error-report.h"
+#include "qemu/guest-random.h"
 
 static bool virt_is_veiointc_enabled(LoongArchVirtMachineState *lvms)
 {
@@ -303,6 +304,7 @@ static void fdt_add_uart_node(LoongArchVirtMachineState *lvms,
 static void create_fdt(LoongArchVirtMachineState *lvms)
 {
     MachineState *ms = MACHINE(lvms);
+    uint8_t rng_seed[32];
 
     ms->fdt = create_device_tree(&lvms->fdt_size);
     if (!ms->fdt) {
@@ -316,6 +318,10 @@ static void create_fdt(LoongArchVirtMachineState *lvms)
     qemu_fdt_setprop_cell(ms->fdt, "/", "#address-cells", 0x2);
     qemu_fdt_setprop_cell(ms->fdt, "/", "#size-cells", 0x2);
     qemu_fdt_add_subnode(ms->fdt, "/chosen");
+
+    /* Pass seed to RNG */
+    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
+    qemu_fdt_setprop(ms->fdt, "/chosen", "rng-seed", rng_seed, sizeof(rng_seed));
 }
 
 static void fdt_add_cpu_nodes(const LoongArchVirtMachineState *lvms)
-- 
2.34.1
Re: [PULL 6/7] hw/loongarch: virt: pass random seed to fdt
Posted by Daniel P. Berrangé 5 days, 7 hours ago 
Hi Song / Jason,

We're seeing non-deterministic hangs in our functional test
suite 'tests/functional/test_loongarch64_virt.py' and my
attempt at git bisect is blaming this commit.

With this applied, perhaps 1 time in 10, the test case hangs,
with zero serial port output from EDK2 emitted

  https://gitlab.com/qemu-project/qemu/-/issues/2686

I'm not seeing an obvious flaw in this commit's code, so I'm
wondering if it has accidentally tickled some other subtle
pre-existing bug elsewhere. Some general problem with FDT
handling on loongarch64 perhaps ?

On Thu, Sep 12, 2024 at 08:51:31PM +0800, Song Gao wrote:
> From: "Jason A. Donenfeld" <Jason@zx2c4.com>
> 
> If the FDT contains /chosen/rng-seed, then the Linux RNG will use it to
> initialize early. Set this using the usual guest random number
> generation function.
> 
> This is the same procedure that's done in b91b6b5a2c ("hw/microblaze:
> pass random seed to fdt"), e4b4f0b71c ("hw/riscv: virt: pass random seed
> to fdt"), c6fe3e6b4c ("hw/openrisc: virt: pass random seed to fdt"),
> 67f7e426e5 ("hw/i386: pass RNG seed via setup_data entry"), c287941a4d
> ("hw/rx: pass random seed to fdt"), 5e19cc68fb ("hw/mips: boston: pass
> random seed to fdt"), 6b23a67916 ("hw/nios2: virt: pass random seed to fdt")
> c4b075318e ("hw/ppc: pass random seed to fdt"), and 5242876f37
> ("hw/arm/virt: dt: add rng-seed property").
> 
> These earlier commits later were amended to rerandomize the RNG seed on
> snapshot load, but the LoongArch code somehow already does that, despite
> not having this patch here, presumably due to some lucky copy and
> pasting.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> Reviewed-by: Song Gao <gaosong@loongson.cn>
> Message-Id: <20240905153316.2038769-1-Jason@zx2c4.com>
> Signed-off-by: Song Gao <gaosong@loongson.cn>
> ---
>  hw/loongarch/virt.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
> index 76dd29a391..81b1f9486f 100644
> --- a/hw/loongarch/virt.c
> +++ b/hw/loongarch/virt.c
> @@ -48,6 +48,7 @@
>  #include "hw/block/flash.h"
>  #include "hw/virtio/virtio-iommu.h"
>  #include "qemu/error-report.h"
> +#include "qemu/guest-random.h"
>  
>  static bool virt_is_veiointc_enabled(LoongArchVirtMachineState *lvms)
>  {
> @@ -303,6 +304,7 @@ static void fdt_add_uart_node(LoongArchVirtMachineState *lvms,
>  static void create_fdt(LoongArchVirtMachineState *lvms)
>  {
>      MachineState *ms = MACHINE(lvms);
> +    uint8_t rng_seed[32];
>  
>      ms->fdt = create_device_tree(&lvms->fdt_size);
>      if (!ms->fdt) {
> @@ -316,6 +318,10 @@ static void create_fdt(LoongArchVirtMachineState *lvms)
>      qemu_fdt_setprop_cell(ms->fdt, "/", "#address-cells", 0x2);
>      qemu_fdt_setprop_cell(ms->fdt, "/", "#size-cells", 0x2);
>      qemu_fdt_add_subnode(ms->fdt, "/chosen");
> +
> +    /* Pass seed to RNG */
> +    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
> +    qemu_fdt_setprop(ms->fdt, "/chosen", "rng-seed", rng_seed, sizeof(rng_seed));
>  }
>  
>  static void fdt_add_cpu_nodes(const LoongArchVirtMachineState *lvms)
> -- 
> 2.34.1
> 
> 

With regards,
Daniel
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Re: [PULL 6/7] hw/loongarch: virt: pass random seed to fdt
Posted by mao bibo 5 days, 1 hour ago 
Hi Daniel,

Thanks for reporting the problem. I can reproduce this problem with my 
local environment, we will investigate this issue ASAP.

Regards
Bibo Mao

On 2024/11/19 上午3:57, Daniel P. Berrangé wrote:
> Hi Song / Jason,
> 
> We're seeing non-deterministic hangs in our functional test
> suite 'tests/functional/test_loongarch64_virt.py' and my
> attempt at git bisect is blaming this commit.
> 
> With this applied, perhaps 1 time in 10, the test case hangs,
> with zero serial port output from EDK2 emitted
> 
>    https://gitlab.com/qemu-project/qemu/-/issues/2686
> 
> I'm not seeing an obvious flaw in this commit's code, so I'm
> wondering if it has accidentally tickled some other subtle
> pre-existing bug elsewhere. Some general problem with FDT
> handling on loongarch64 perhaps ?
> 
> On Thu, Sep 12, 2024 at 08:51:31PM +0800, Song Gao wrote:
>> From: "Jason A. Donenfeld" <Jason@zx2c4.com>
>>
>> If the FDT contains /chosen/rng-seed, then the Linux RNG will use it to
>> initialize early. Set this using the usual guest random number
>> generation function.
>>
>> This is the same procedure that's done in b91b6b5a2c ("hw/microblaze:
>> pass random seed to fdt"), e4b4f0b71c ("hw/riscv: virt: pass random seed
>> to fdt"), c6fe3e6b4c ("hw/openrisc: virt: pass random seed to fdt"),
>> 67f7e426e5 ("hw/i386: pass RNG seed via setup_data entry"), c287941a4d
>> ("hw/rx: pass random seed to fdt"), 5e19cc68fb ("hw/mips: boston: pass
>> random seed to fdt"), 6b23a67916 ("hw/nios2: virt: pass random seed to fdt")
>> c4b075318e ("hw/ppc: pass random seed to fdt"), and 5242876f37
>> ("hw/arm/virt: dt: add rng-seed property").
>>
>> These earlier commits later were amended to rerandomize the RNG seed on
>> snapshot load, but the LoongArch code somehow already does that, despite
>> not having this patch here, presumably due to some lucky copy and
>> pasting.
>>
>> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
>> Reviewed-by: Song Gao <gaosong@loongson.cn>
>> Message-Id: <20240905153316.2038769-1-Jason@zx2c4.com>
>> Signed-off-by: Song Gao <gaosong@loongson.cn>
>> ---
>>   hw/loongarch/virt.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
>> index 76dd29a391..81b1f9486f 100644
>> --- a/hw/loongarch/virt.c
>> +++ b/hw/loongarch/virt.c
>> @@ -48,6 +48,7 @@
>>   #include "hw/block/flash.h"
>>   #include "hw/virtio/virtio-iommu.h"
>>   #include "qemu/error-report.h"
>> +#include "qemu/guest-random.h"
>>   
>>   static bool virt_is_veiointc_enabled(LoongArchVirtMachineState *lvms)
>>   {
>> @@ -303,6 +304,7 @@ static void fdt_add_uart_node(LoongArchVirtMachineState *lvms,
>>   static void create_fdt(LoongArchVirtMachineState *lvms)
>>   {
>>       MachineState *ms = MACHINE(lvms);
>> +    uint8_t rng_seed[32];
>>   
>>       ms->fdt = create_device_tree(&lvms->fdt_size);
>>       if (!ms->fdt) {
>> @@ -316,6 +318,10 @@ static void create_fdt(LoongArchVirtMachineState *lvms)
>>       qemu_fdt_setprop_cell(ms->fdt, "/", "#address-cells", 0x2);
>>       qemu_fdt_setprop_cell(ms->fdt, "/", "#size-cells", 0x2);
>>       qemu_fdt_add_subnode(ms->fdt, "/chosen");
>> +
>> +    /* Pass seed to RNG */
>> +    qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
>> +    qemu_fdt_setprop(ms->fdt, "/chosen", "rng-seed", rng_seed, sizeof(rng_seed));
>>   }
>>   
>>   static void fdt_add_cpu_nodes(const LoongArchVirtMachineState *lvms)
>> -- 
>> 2.34.1
>>
>>
> 
> With regards,
> Daniel
>

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