2023-06-07 10:57:28

by Kai Huang

Subject: [PATCH] x86/kexec: Add a comment to relocate_kernel() for better readability

The reason to save %rcx to %r11 before calling swap_pages isn't that
obvious w/o looking into the swap_pages itself. Add a comment to
improve the readability.

Signed-off-by: Kai Huang <[email protected]>
---
arch/x86/kernel/relocate_kernel_64.S | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 56cab1bb25f5..97deae3c5e6c 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -169,6 +169,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
wbinvd
1:

+ /*
+ * Save the preserve_context to %r11 as
+ * swap_pages clobbers %rcx.
+ */
movq %rcx, %r11
call swap_pages


base-commit: 409bf2895d71bb68bc5b8589036e5ed1ca30bada
--
2.40.1

2023-06-07 11:48:43

by Kirill A. Shutemov

Subject: Re: [PATCH] x86/kexec: Add a comment to relocate_kernel() for better readability

On Wed, Jun 07, 2023 at 10:39:10PM +1200, Kai Huang wrote:
> The reason to save %rcx to %r11 before calling swap_pages isn't that
> obvious w/o looking into the swap_pages itself. Add a comment to
> improve the readability.
>
> Signed-off-by: Kai Huang <[email protected]>
> ---
> arch/x86/kernel/relocate_kernel_64.S | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
> index 56cab1bb25f5..97deae3c5e6c 100644
> --- a/arch/x86/kernel/relocate_kernel_64.S
> +++ b/arch/x86/kernel/relocate_kernel_64.S
> @@ -169,6 +169,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
> wbinvd
> 1:
>
> + /*
> + * Save the preserve_context to %r11 as
> + * swap_pages clobbers %rcx.
> + */

Line split is not needed. It fits nicely under 80-characters.

+ /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */

Otherwise, LGTM.

> movq %rcx, %r11
> call swap_pages
>
>
> base-commit: 409bf2895d71bb68bc5b8589036e5ed1ca30bada
> --
> 2.40.1
>

--
Kiryl Shutsemau / Kirill A. Shutemov

2023-06-08 04:53:26

by Kai Huang

Subject: Re: [PATCH] x86/kexec: Add a comment to relocate_kernel() for better readability

On Wed, 2023-06-07 at 14:19 +0300, [email protected] wrote:
> On Wed, Jun 07, 2023 at 10:39:10PM +1200, Kai Huang wrote:
> > The reason to save %rcx to %r11 before calling swap_pages isn't that
> > obvious w/o looking into the swap_pages itself. Add a comment to
> > improve the readability.
> >
> > Signed-off-by: Kai Huang <[email protected]>
> > ---
> > arch/x86/kernel/relocate_kernel_64.S | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
> > index 56cab1bb25f5..97deae3c5e6c 100644
> > --- a/arch/x86/kernel/relocate_kernel_64.S
> > +++ b/arch/x86/kernel/relocate_kernel_64.S
> > @@ -169,6 +169,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
> > wbinvd
> > 1:
> >
> > + /*
> > + * Save the preserve_context to %r11 as
> > + * swap_pages clobbers %rcx.
> > + */
>
> Line split is not needed. It fits nicely under 80-characters.
>
> + /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */
>
> Otherwise, LGTM.

Sure. Will do.

With above change, may I add your Acked-by ? :)

>
> > movq %rcx, %r11
> > call swap_pages
> >
> >
> > base-commit: 409bf2895d71bb68bc5b8589036e5ed1ca30bada
> > --
> > 2.40.1
> >
>

2023-06-08 11:32:56

by Kirill A. Shutemov

Subject: Re: [PATCH] x86/kexec: Add a comment to relocate_kernel() for better readability

On Thu, Jun 08, 2023 at 04:41:37AM +0000, Huang, Kai wrote:
> On Wed, 2023-06-07 at 14:19 +0300, [email protected] wrote:
> > On Wed, Jun 07, 2023 at 10:39:10PM +1200, Kai Huang wrote:
> > > The reason to save %rcx to %r11 before calling swap_pages isn't that
> > > obvious w/o looking into the swap_pages itself. Add a comment to
> > > improve the readability.
> > >
> > > Signed-off-by: Kai Huang <[email protected]>
> > > ---
> > > arch/x86/kernel/relocate_kernel_64.S | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
> > > index 56cab1bb25f5..97deae3c5e6c 100644
> > > --- a/arch/x86/kernel/relocate_kernel_64.S
> > > +++ b/arch/x86/kernel/relocate_kernel_64.S
> > > @@ -169,6 +169,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
> > > wbinvd
> > > 1:
> > >
> > > + /*
> > > + * Save the preserve_context to %r11 as
> > > + * swap_pages clobbers %rcx.
> > > + */
> >
> > Line split is not needed. It fits nicely under 80-characters.
> >
> > + /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */
> >
> > Otherwise, LGTM.
>
> Sure. Will do.
>
> With above change, may I add your Acked-by ? :)

Sure.

--
Kiryl Shutsemau / Kirill A. Shutemov