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[PATCH v2] hw: riscv: Allow large kernels to boot by moving the initrd further away in RAM

Alexandre Ghiti posted 1 patch 9 months, 3 weeks ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20240206154042.514698-1-alexghiti@rivosinc.com
Maintainers: Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Bin Meng <bin.meng@windriver.com>, Weiwei Li <liwei1518@gmail.com>, Daniel Henrique Barboza <dbarboza@ventanamicro.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>
hw/riscv/boot.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
[PATCH v2] hw: riscv: Allow large kernels to boot by moving the initrd further away in RAM
Posted by Alexandre Ghiti 9 months, 3 weeks ago 
Currently, the initrd is placed at 128MB, which overlaps with the kernel
when it is large (for example syzbot kernels are). From the kernel side,
there is no reason we could not push the initrd further away in memory
to accommodate large kernels, so move the initrd at 512MB when possible.

The ideal solution would have been to place the initrd based on the
kernel size but we actually can't since the bss size is not known when
the image is loaded by load_image_targphys_as() and the initrd would
then overlap with this section.

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---

Changes in v2:
- Fix typos in commit log (Daniel) and title
- Added to the commit log why using the kernel size does not work
  (Daniel)

 hw/riscv/boot.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
index 0ffca05189..9a367af2fa 100644
--- a/hw/riscv/boot.c
+++ b/hw/riscv/boot.c
@@ -188,13 +188,13 @@ static void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry)
      * kernel is uncompressed it will not clobber the initrd. However
      * on boards without much RAM we must ensure that we still leave
      * enough room for a decent sized initrd, and on boards with large
-     * amounts of RAM we must avoid the initrd being so far up in RAM
-     * that it is outside lowmem and inaccessible to the kernel.
-     * So for boards with less  than 256MB of RAM we put the initrd
-     * halfway into RAM, and for boards with 256MB of RAM or more we put
-     * the initrd at 128MB.
+     * amounts of RAM, we put the initrd at 512MB to allow large kernels
+     * to boot.
+     * So for boards with less than 1GB of RAM we put the initrd
+     * halfway into RAM, and for boards with 1GB of RAM or more we put
+     * the initrd at 512MB.
      */
-    start = kernel_entry + MIN(mem_size / 2, 128 * MiB);
+    start = kernel_entry + MIN(mem_size / 2, 512 * MiB);
 
     size = load_ramdisk(filename, start, mem_size - start);
     if (size == -1) {
-- 
2.39.2
Re: [PATCH v2] hw: riscv: Allow large kernels to boot by moving the initrd further away in RAM
Posted by Alistair Francis 9 months, 2 weeks ago 
On Wed, Feb 7, 2024 at 1:42 AM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>
> Currently, the initrd is placed at 128MB, which overlaps with the kernel
> when it is large (for example syzbot kernels are). From the kernel side,
> there is no reason we could not push the initrd further away in memory
> to accommodate large kernels, so move the initrd at 512MB when possible.
>
> The ideal solution would have been to place the initrd based on the
> kernel size but we actually can't since the bss size is not known when
> the image is loaded by load_image_targphys_as() and the initrd would
> then overlap with this section.
>
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
>
> Changes in v2:
> - Fix typos in commit log (Daniel) and title
> - Added to the commit log why using the kernel size does not work
>   (Daniel)
>
>  hw/riscv/boot.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> index 0ffca05189..9a367af2fa 100644
> --- a/hw/riscv/boot.c
> +++ b/hw/riscv/boot.c
> @@ -188,13 +188,13 @@ static void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry)
>       * kernel is uncompressed it will not clobber the initrd. However
>       * on boards without much RAM we must ensure that we still leave
>       * enough room for a decent sized initrd, and on boards with large
> -     * amounts of RAM we must avoid the initrd being so far up in RAM
> -     * that it is outside lowmem and inaccessible to the kernel.
> -     * So for boards with less  than 256MB of RAM we put the initrd
> -     * halfway into RAM, and for boards with 256MB of RAM or more we put
> -     * the initrd at 128MB.
> +     * amounts of RAM, we put the initrd at 512MB to allow large kernels
> +     * to boot.
> +     * So for boards with less than 1GB of RAM we put the initrd
> +     * halfway into RAM, and for boards with 1GB of RAM or more we put
> +     * the initrd at 512MB.
>       */
> -    start = kernel_entry + MIN(mem_size / 2, 128 * MiB);
> +    start = kernel_entry + MIN(mem_size / 2, 512 * MiB);
>
>      size = load_ramdisk(filename, start, mem_size - start);
>      if (size == -1) {
> --
> 2.39.2
>
>
Re: [PATCH v2] hw: riscv: Allow large kernels to boot by moving the initrd further away in RAM
Posted by Alistair Francis 9 months, 2 weeks ago 
On Wed, Feb 7, 2024 at 1:42 AM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>
> Currently, the initrd is placed at 128MB, which overlaps with the kernel
> when it is large (for example syzbot kernels are). From the kernel side,
> there is no reason we could not push the initrd further away in memory
> to accommodate large kernels, so move the initrd at 512MB when possible.
>
> The ideal solution would have been to place the initrd based on the
> kernel size but we actually can't since the bss size is not known when
> the image is loaded by load_image_targphys_as() and the initrd would
> then overlap with this section.
>
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>
> Changes in v2:
> - Fix typos in commit log (Daniel) and title
> - Added to the commit log why using the kernel size does not work
>   (Daniel)
>
>  hw/riscv/boot.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> index 0ffca05189..9a367af2fa 100644
> --- a/hw/riscv/boot.c
> +++ b/hw/riscv/boot.c
> @@ -188,13 +188,13 @@ static void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry)
>       * kernel is uncompressed it will not clobber the initrd. However
>       * on boards without much RAM we must ensure that we still leave
>       * enough room for a decent sized initrd, and on boards with large
> -     * amounts of RAM we must avoid the initrd being so far up in RAM
> -     * that it is outside lowmem and inaccessible to the kernel.
> -     * So for boards with less  than 256MB of RAM we put the initrd
> -     * halfway into RAM, and for boards with 256MB of RAM or more we put
> -     * the initrd at 128MB.
> +     * amounts of RAM, we put the initrd at 512MB to allow large kernels
> +     * to boot.
> +     * So for boards with less than 1GB of RAM we put the initrd
> +     * halfway into RAM, and for boards with 1GB of RAM or more we put
> +     * the initrd at 512MB.
>       */
> -    start = kernel_entry + MIN(mem_size / 2, 128 * MiB);
> +    start = kernel_entry + MIN(mem_size / 2, 512 * MiB);
>
>      size = load_ramdisk(filename, start, mem_size - start);
>      if (size == -1) {
> --
> 2.39.2
>
>
Re: [PATCH v2] hw: riscv: Allow large kernels to boot by moving the initrd further away in RAM
Posted by Daniel Henrique Barboza 9 months, 3 weeks ago 

On 2/6/24 12:40, Alexandre Ghiti wrote:
> Currently, the initrd is placed at 128MB, which overlaps with the kernel
> when it is large (for example syzbot kernels are). From the kernel side,
> there is no reason we could not push the initrd further away in memory
> to accommodate large kernels, so move the initrd at 512MB when possible.
> 
> The ideal solution would have been to place the initrd based on the
> kernel size but we actually can't since the bss size is not known when
> the image is loaded by load_image_targphys_as() and the initrd would
> then overlap with this section.
> 
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---

Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

> 
> Changes in v2:
> - Fix typos in commit log (Daniel) and title
> - Added to the commit log why using the kernel size does not work
>    (Daniel)
> 
>   hw/riscv/boot.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> index 0ffca05189..9a367af2fa 100644
> --- a/hw/riscv/boot.c
> +++ b/hw/riscv/boot.c
> @@ -188,13 +188,13 @@ static void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry)
>        * kernel is uncompressed it will not clobber the initrd. However
>        * on boards without much RAM we must ensure that we still leave
>        * enough room for a decent sized initrd, and on boards with large
> -     * amounts of RAM we must avoid the initrd being so far up in RAM
> -     * that it is outside lowmem and inaccessible to the kernel.
> -     * So for boards with less  than 256MB of RAM we put the initrd
> -     * halfway into RAM, and for boards with 256MB of RAM or more we put
> -     * the initrd at 128MB.
> +     * amounts of RAM, we put the initrd at 512MB to allow large kernels
> +     * to boot.
> +     * So for boards with less than 1GB of RAM we put the initrd
> +     * halfway into RAM, and for boards with 1GB of RAM or more we put
> +     * the initrd at 512MB.
>        */
> -    start = kernel_entry + MIN(mem_size / 2, 128 * MiB);
> +    start = kernel_entry + MIN(mem_size / 2, 512 * MiB);
>   
>       size = load_ramdisk(filename, start, mem_size - start);
>       if (size == -1) {
Re: [PATCH v2] hw: riscv: Allow large kernels to boot by moving the initrd further away in RAM
Posted by Alexandre Ghiti 9 months, 3 weeks ago 
On Tue, Feb 6, 2024 at 9:39 PM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
>
>
> On 2/6/24 12:40, Alexandre Ghiti wrote:
> > Currently, the initrd is placed at 128MB, which overlaps with the kernel
> > when it is large (for example syzbot kernels are). From the kernel side,
> > there is no reason we could not push the initrd further away in memory
> > to accommodate large kernels, so move the initrd at 512MB when possible.
> >
> > The ideal solution would have been to place the initrd based on the
> > kernel size but we actually can't since the bss size is not known when
> > the image is loaded by load_image_targphys_as() and the initrd would
> > then overlap with this section.
> >
> > Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> > ---
>
> Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Thanks for your help!

Alex

>
> >
> > Changes in v2:
> > - Fix typos in commit log (Daniel) and title
> > - Added to the commit log why using the kernel size does not work
> >    (Daniel)
> >
> >   hw/riscv/boot.c | 12 ++++++------
> >   1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> > index 0ffca05189..9a367af2fa 100644
> > --- a/hw/riscv/boot.c
> > +++ b/hw/riscv/boot.c
> > @@ -188,13 +188,13 @@ static void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry)
> >        * kernel is uncompressed it will not clobber the initrd. However
> >        * on boards without much RAM we must ensure that we still leave
> >        * enough room for a decent sized initrd, and on boards with large
> > -     * amounts of RAM we must avoid the initrd being so far up in RAM
> > -     * that it is outside lowmem and inaccessible to the kernel.
> > -     * So for boards with less  than 256MB of RAM we put the initrd
> > -     * halfway into RAM, and for boards with 256MB of RAM or more we put
> > -     * the initrd at 128MB.
> > +     * amounts of RAM, we put the initrd at 512MB to allow large kernels
> > +     * to boot.
> > +     * So for boards with less than 1GB of RAM we put the initrd
> > +     * halfway into RAM, and for boards with 1GB of RAM or more we put
> > +     * the initrd at 512MB.
> >        */
> > -    start = kernel_entry + MIN(mem_size / 2, 128 * MiB);
> > +    start = kernel_entry + MIN(mem_size / 2, 512 * MiB);
> >
> >       size = load_ramdisk(filename, start, mem_size - start);
> >       if (size == -1) {

Patchew 2.1-devel-b67e4c2

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