* [PATCH 0/2] x86: more flexible alignment handling for xen binary
@ 2019-03-18 14:57 Wei Liu
2019-03-18 14:57 ` [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build Wei Liu
2019-03-18 14:57 ` [PATCH 2/2] x86/pvshim: use 2M alignment Wei Liu
0 siblings, 2 replies; 6+ messages in thread
From: Wei Liu @ 2019-03-18 14:57 UTC (permalink / raw)
To: xen-devel; +Cc: Wei Liu
Wei Liu (2):
x86: decouple xen alignment setting from EFI/non-EFI build
x86/pvshim: use 2M alignment
xen/arch/x86/Kconfig | 26 ++++++++++++++++++++++++++
xen/arch/x86/configs/pvshim_defconfig | 1 +
xen/arch/x86/xen.lds.S | 16 ++++++++++++++--
3 files changed, 41 insertions(+), 2 deletions(-)
--
2.20.1
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build
2019-03-18 14:57 [PATCH 0/2] x86: more flexible alignment handling for xen binary Wei Liu
@ 2019-03-18 14:57 ` Wei Liu
2019-03-19 10:45 ` Jan Beulich
2019-03-18 14:57 ` [PATCH 2/2] x86/pvshim: use 2M alignment Wei Liu
1 sibling, 1 reply; 6+ messages in thread
From: Wei Liu @ 2019-03-18 14:57 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Wei Liu, Jan Beulich, Roger Pau Monné
Introduce a new Kconfig option to pick the alignment for xen binary.
To retain original behaviour, the default pick for EFI build is 2M and
non-EFI build 4K.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
xen/arch/x86/Kconfig | 26 ++++++++++++++++++++++++++
xen/arch/x86/xen.lds.S | 16 ++++++++++++++--
2 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 5c2d1070b6..b15053cfbe 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -138,6 +138,32 @@ config TBOOT
If unsure, say Y.
+choice
+ prompt "Alignment of Xen binary"
+ depends on X86
+ default XEN_ALIGN_DEFAULT
+ ---help---
+ Specify alignment for Xen binary.
+
+ If unsure, choose "default".
+
+config XEN_ALIGN_DEFAULT
+ bool "Default alignment"
+ ---help---
+ Pick alignment according to build variants.
+
+ For EFI build the default alignment is 2M. For non-EFI build
+ the default alignment is 4K due to syslinux failing to handle
+ 2M alignment.
+
+config XEN_ALIGN_4K
+ bool "4K alignment"
+
+config XEN_ALIGN_2M
+ bool "2M alignment"
+
+endchoice
+
config XEN_GUEST
def_bool n
prompt "Xen Guest"
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 6e9bda5109..163de31574 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -12,7 +12,6 @@
#define FORMAT "pei-x86-64"
#undef __XEN_VIRT_START
#define __XEN_VIRT_START __image_base__
-#define SECTION_ALIGN MB(2)
#define DECL_SECTION(x) x :
ENTRY(efi_start)
@@ -20,13 +19,26 @@ ENTRY(efi_start)
#else /* !EFI */
#define FORMAT "elf64-x86-64"
-#define SECTION_ALIGN PAGE_SIZE
#define DECL_SECTION(x) x : AT(ADDR(x) - __XEN_VIRT_START)
ENTRY(start_pa)
#endif /* EFI */
+#if defined CONFIG_XEN_ALIGN_2M
+#define SECTION_ALIGN MB(2)
+#elif defined CONFIG_XEN_ALIGN_4K
+#define SECTION_ALIGN PAGE_SIZE
+#elif defined CONFIG_XEN_ALIGN_DEFAULT
+ #ifdef EFI
+ #define SECTION_ALIGN MB(2)
+ #else
+ #define SECTION_ALIGN PAGE_SIZE
+ #endif
+#else
+#error "Section alignment undefined"
+#endif
+
OUTPUT_FORMAT(FORMAT, FORMAT, FORMAT)
OUTPUT_ARCH(i386:x86-64)
--
2.20.1
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] x86/pvshim: use 2M alignment
2019-03-18 14:57 [PATCH 0/2] x86: more flexible alignment handling for xen binary Wei Liu
2019-03-18 14:57 ` [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build Wei Liu
@ 2019-03-18 14:57 ` Wei Liu
1 sibling, 0 replies; 6+ messages in thread
From: Wei Liu @ 2019-03-18 14:57 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Wei Liu, Jan Beulich, Roger Pau Monné
The pvshim is loaded directly by toolstack. Use 2M alignment for
potential better performance.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
xen/arch/x86/configs/pvshim_defconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/xen/arch/x86/configs/pvshim_defconfig b/xen/arch/x86/configs/pvshim_defconfig
index a12e3d0465..8e50b60cda 100644
--- a/xen/arch/x86/configs/pvshim_defconfig
+++ b/xen/arch/x86/configs/pvshim_defconfig
@@ -5,6 +5,7 @@ CONFIG_PVH_GUEST=y
CONFIG_PV_SHIM=y
CONFIG_PV_SHIM_EXCLUSIVE=y
CONFIG_NR_CPUS=32
+CONFIG_XEN_ALIGN_2M=y
# Disable features not used by the PV shim
# CONFIG_SHADOW_PAGING is not set
# CONFIG_BIGMEM is not set
--
2.20.1
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build
2019-03-18 14:57 ` [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build Wei Liu
@ 2019-03-19 10:45 ` Jan Beulich
2019-03-19 11:24 ` Wei Liu
0 siblings, 1 reply; 6+ messages in thread
From: Jan Beulich @ 2019-03-19 10:45 UTC (permalink / raw)
To: Wei Liu; +Cc: Andrew Cooper, xen-devel, Roger Pau Monne
>>> On 18.03.19 at 15:57, <wei.liu2@citrix.com> wrote:
> Introduce a new Kconfig option to pick the alignment for xen binary.
> To retain original behaviour, the default pick for EFI build is 2M and
> non-EFI build 4K.
Is this a worthwhile step to take, considering that we mean to
switch to 2M main section boundaries anyway? I realize it's still not
necessarily clear how to get there without re-introducing the boot
regression with syslinux that was observed back then, but perhaps
time would better be spent there than into introducing configurability?
(To be honest I don't recall whether it was determined that there
was no way out of this dilemma, but it seems to me there would
have been a plan.)
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -138,6 +138,32 @@ config TBOOT
>
> If unsure, say Y.
>
> +choice
> + prompt "Alignment of Xen binary"
> + depends on X86
> + default XEN_ALIGN_DEFAULT
> + ---help---
> + Specify alignment for Xen binary.
> +
> + If unsure, choose "default".
> +
> +config XEN_ALIGN_DEFAULT
> + bool "Default alignment"
> + ---help---
> + Pick alignment according to build variants.
> +
> + For EFI build the default alignment is 2M. For non-EFI build
> + the default alignment is 4K due to syslinux failing to handle
> + 2M alignment.
Wasn't it the resulting image size rather than the alignment itself
which did cause the problem? Has the issue been fixed in newer
syslinux?
> +config XEN_ALIGN_4K
> + bool "4K alignment"
> +
> +config XEN_ALIGN_2M
> + bool "2M alignment"
In patch 2 you only need the latter - is there really much value in
allowing explicitly requesting 4k?
> @@ -20,13 +19,26 @@ ENTRY(efi_start)
> #else /* !EFI */
>
> #define FORMAT "elf64-x86-64"
> -#define SECTION_ALIGN PAGE_SIZE
> #define DECL_SECTION(x) x : AT(ADDR(x) - __XEN_VIRT_START)
>
> ENTRY(start_pa)
>
> #endif /* EFI */
>
> +#if defined CONFIG_XEN_ALIGN_2M
> +#define SECTION_ALIGN MB(2)
> +#elif defined CONFIG_XEN_ALIGN_4K
> +#define SECTION_ALIGN PAGE_SIZE
> +#elif defined CONFIG_XEN_ALIGN_DEFAULT
> + #ifdef EFI
> + #define SECTION_ALIGN MB(2)
> + #else
> + #define SECTION_ALIGN PAGE_SIZE
> + #endif
> +#else
> +#error "Section alignment undefined"
> +#endif
How about converting the last #elif to #else and omitting the
#error? Also would you mind using the defined() style (i.e. with
parentheses), as we commonly do elsewhere? And please use
uniform indentation (or not) of directives. I also find the
indentation itself quite unusual - we have almost no examples of
it being like this outside of files we've imported from elsewhere.
Typically we retain the # in column 1 and indent only the actual
directive keyword.
Jan
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build
2019-03-19 10:45 ` Jan Beulich
@ 2019-03-19 11:24 ` Wei Liu
2019-03-19 12:48 ` Jan Beulich
0 siblings, 1 reply; 6+ messages in thread
From: Wei Liu @ 2019-03-19 11:24 UTC (permalink / raw)
To: Jan Beulich; +Cc: Andrew Cooper, Wei Liu, xen-devel, Roger Pau Monne
On Tue, Mar 19, 2019 at 04:45:35AM -0600, Jan Beulich wrote:
> >>> On 18.03.19 at 15:57, <wei.liu2@citrix.com> wrote:
> > Introduce a new Kconfig option to pick the alignment for xen binary.
> > To retain original behaviour, the default pick for EFI build is 2M and
> > non-EFI build 4K.
>
> Is this a worthwhile step to take, considering that we mean to
> switch to 2M main section boundaries anyway? I realize it's still not
> necessarily clear how to get there without re-introducing the boot
> regression with syslinux that was observed back then, but perhaps
> time would better be spent there than into introducing configurability?
> (To be honest I don't recall whether it was determined that there
> was no way out of this dilemma, but it seems to me there would
> have been a plan.)
I think it would definitely be sensible to fix it there. But we still
have older syslinux to deal with. I don't think they're going away any
time soon.
>
> > --- a/xen/arch/x86/Kconfig
> > +++ b/xen/arch/x86/Kconfig
> > @@ -138,6 +138,32 @@ config TBOOT
> >
> > If unsure, say Y.
> >
> > +choice
> > + prompt "Alignment of Xen binary"
> > + depends on X86
> > + default XEN_ALIGN_DEFAULT
> > + ---help---
> > + Specify alignment for Xen binary.
> > +
> > + If unsure, choose "default".
> > +
> > +config XEN_ALIGN_DEFAULT
> > + bool "Default alignment"
> > + ---help---
> > + Pick alignment according to build variants.
> > +
> > + For EFI build the default alignment is 2M. For non-EFI build
> > + the default alignment is 4K due to syslinux failing to handle
> > + 2M alignment.
>
> Wasn't it the resulting image size rather than the alignment itself
> which did cause the problem? Has the issue been fixed in newer
> syslinux?
>
Right. I can make this clearer.
"due to syslinux failing to handle the image size increment induced by
2M alignment".
Also, I think s/binary/image/ in the description would be better.
Looking at syslinux.git I don't immediately see patches to fix the issue
(if there is such issue in the first place).
> > +config XEN_ALIGN_4K
> > + bool "4K alignment"
> > +
> > +config XEN_ALIGN_2M
> > + bool "2M alignment"
>
> In patch 2 you only need the latter - is there really much value in
> allowing explicitly requesting 4k?
>
I thought there would be a case in which users want 4K explicitly? I'm
certainly fine with dropping the 4K alignment option.
> > @@ -20,13 +19,26 @@ ENTRY(efi_start)
> > #else /* !EFI */
> >
> > #define FORMAT "elf64-x86-64"
> > -#define SECTION_ALIGN PAGE_SIZE
> > #define DECL_SECTION(x) x : AT(ADDR(x) - __XEN_VIRT_START)
> >
> > ENTRY(start_pa)
> >
> > #endif /* EFI */
> >
> > +#if defined CONFIG_XEN_ALIGN_2M
> > +#define SECTION_ALIGN MB(2)
> > +#elif defined CONFIG_XEN_ALIGN_4K
> > +#define SECTION_ALIGN PAGE_SIZE
> > +#elif defined CONFIG_XEN_ALIGN_DEFAULT
> > + #ifdef EFI
> > + #define SECTION_ALIGN MB(2)
> > + #else
> > + #define SECTION_ALIGN PAGE_SIZE
> > + #endif
> > +#else
> > +#error "Section alignment undefined"
> > +#endif
>
> How about converting the last #elif to #else and omitting the
> #error? Also would you mind using the defined() style (i.e. with
> parentheses), as we commonly do elsewhere? And please use
> uniform indentation (or not) of directives. I also find the
> indentation itself quite unusual - we have almost no examples of
> it being like this outside of files we've imported from elsewhere.
> Typically we retain the # in column 1 and indent only the actual
> directive keyword.
Will fix (after we determine what to do with 4K option).
Wei.
>
> Jan
>
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build
2019-03-19 11:24 ` Wei Liu
@ 2019-03-19 12:48 ` Jan Beulich
0 siblings, 0 replies; 6+ messages in thread
From: Jan Beulich @ 2019-03-19 12:48 UTC (permalink / raw)
To: Wei Liu; +Cc: Andrew Cooper, xen-devel, Roger Pau Monne
>>> On 19.03.19 at 12:24, <wei.liu2@citrix.com> wrote:
> On Tue, Mar 19, 2019 at 04:45:35AM -0600, Jan Beulich wrote:
>> >>> On 18.03.19 at 15:57, <wei.liu2@citrix.com> wrote:
>> > --- a/xen/arch/x86/Kconfig
>> > +++ b/xen/arch/x86/Kconfig
>> > @@ -138,6 +138,32 @@ config TBOOT
>> >
>> > If unsure, say Y.
>> >
>> > +choice
>> > + prompt "Alignment of Xen binary"
>> > + depends on X86
>> > + default XEN_ALIGN_DEFAULT
>> > + ---help---
>> > + Specify alignment for Xen binary.
>> > +
>> > + If unsure, choose "default".
>> > +
>> > +config XEN_ALIGN_DEFAULT
>> > + bool "Default alignment"
>> > + ---help---
>> > + Pick alignment according to build variants.
>> > +
>> > + For EFI build the default alignment is 2M. For non-EFI build
>> > + the default alignment is 4K due to syslinux failing to handle
>> > + 2M alignment.
>>
>> Wasn't it the resulting image size rather than the alignment itself
>> which did cause the problem? Has the issue been fixed in newer
>> syslinux?
>>
>
> Right. I can make this clearer.
>
> "due to syslinux failing to handle the image size increment induced by
> 2M alignment".
>
> Also, I think s/binary/image/ in the description would be better.
Agreed.
>> > +config XEN_ALIGN_4K
>> > + bool "4K alignment"
>> > +
>> > +config XEN_ALIGN_2M
>> > + bool "2M alignment"
>>
>> In patch 2 you only need the latter - is there really much value in
>> allowing explicitly requesting 4k?
>
> I thought there would be a case in which users want 4K explicitly? I'm
> certainly fine with dropping the 4K alignment option.
Well, without a specific need or request I'd prefer not to see extra
options introduced.
Jan
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-03-19 12:48 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2019-03-18 14:57 [PATCH 0/2] x86: more flexible alignment handling for xen binary Wei Liu
2019-03-18 14:57 ` [PATCH 1/2] x86: decouple xen alignment setting from EFI/non-EFI build Wei Liu
2019-03-19 10:45 ` Jan Beulich
2019-03-19 11:24 ` Wei Liu
2019-03-19 12:48 ` Jan Beulich
2019-03-18 14:57 ` [PATCH 2/2] x86/pvshim: use 2M alignment Wei Liu
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