[PATCH kvmtool 0/1] Don't empty CFLAGS in Makefile for static building

[PATCH kvmtool 0/1] Don't empty CFLAGS in Makefile for static building

[Yao Yuan]

Don't set the CFLAGS to empty in Makefile for passing more
CFLAGS options from environment variable, e.g -static for
native static building.

One use case of static buidling is using kvmtool for
pre-silicon validation on emulation system, such system has
limited or even no IO part and run w/ small solo ramdisk as
linux userspace instead of full Linux distribution, and run
in slow speed. Thus the self-contained kvmtool static
building is good choice in performance and size for testing
on such system.

The static building is verified on arm64 host:

CFLAGS=-static make -j32
...
LINK     lkvm
LN       vm

$ldd ./lkvm
        not a dynamic executable

The funciton is verified w/ below command, boot arm64 guest
to serial successfully:

cmdline=(
	ignore_loglevel
	earlycon=uart8250,mmio,0x1000000,115200n8
	console=uart8250,mmio,0x1000000,115200n8
	nokaslr
	selinux=0
	audit=0
	root=/dev/vda3
)

./lkvm run \
	   --name test_kvmtool \
	   -c 4 -m 1G \
	   --nodefaults \
	   --irqchip gicv3-its \
	   --console serial \
	   --virtio-transport pci \
	   --disk /path/to/the/disk/image
	   --kernel /path/to/the/arm64/boot/image
	   --param "${cmdline[*]}"


Yao Yuan (1):
  Makefile: Don't set -CFLAGS := in Makefile

 Makefile | 1 -
 1 file changed, 1 deletion(-)

--
2.43.5

[PATCH kvmtool 1/1] Makefile: Don't set -CFLAGS := in Makefile

[Yao Yuan]

Don't set CFLAGS to empty in the Makefile to allow
set the addtional CFLAGS option from environment,
support e.g native static compiling.

Signed-off-by: Yao Yuan <yaoyuan@linux.alibaba.com>
---
 Makefile | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Makefile b/Makefile
index 60e551f..6755910 100644
--- a/Makefile
+++ b/Makefile
@@ -20,7 +20,6 @@ include config/feature-tests.mak
 -include $(OUTPUT)KVMTOOLS-VERSION-FILE
 
 CC	:= $(CROSS_COMPILE)gcc
-CFLAGS	:=
 LD	:= $(CROSS_COMPILE)ld
 LDFLAGS	:=
 OBJCOPY	:= $(CROSS_COMPILE)objcopy
-- 
2.43.5

Re: [PATCH kvmtool 0/1] Don't empty CFLAGS in Makefile for static building

[Alexandru Elisei]

Hi,

On Mon, Aug 17, 2026 at 04:45:33PM +0800, Yao Yuan wrote:
> Don't set the CFLAGS to empty in Makefile for passing more
> CFLAGS options from environment variable, e.g -static for
> native static building.

I think the lkvm-static makefile target might be your friend in this case :)

$ make -j$(getconf _NPROCESSORS_ONLN) ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- lkvm-static

(have a look at the $(PROGRAM)-static target if you want to double check that it
fits your needs)

Thanks,
Alex

> 
> One use case of static buidling is using kvmtool for
> pre-silicon validation on emulation system, such system has
> limited or even no IO part and run w/ small solo ramdisk as
> linux userspace instead of full Linux distribution, and run
> in slow speed. Thus the self-contained kvmtool static
> building is good choice in performance and size for testing
> on such system.
> 
> The static building is verified on arm64 host:
> 
> CFLAGS=-static make -j32
> ...
> LINK     lkvm
> LN       vm
> 
> $ldd ./lkvm
>         not a dynamic executable
> 
> The funciton is verified w/ below command, boot arm64 guest
> to serial successfully:
> 
> cmdline=(
> 	ignore_loglevel
> 	earlycon=uart8250,mmio,0x1000000,115200n8
> 	console=uart8250,mmio,0x1000000,115200n8
> 	nokaslr
> 	selinux=0
> 	audit=0
> 	root=/dev/vda3
> )
> 
> ./lkvm run \
> 	   --name test_kvmtool \
> 	   -c 4 -m 1G \
> 	   --nodefaults \
> 	   --irqchip gicv3-its \
> 	   --console serial \
> 	   --virtio-transport pci \
> 	   --disk /path/to/the/disk/image
> 	   --kernel /path/to/the/arm64/boot/image
> 	   --param "${cmdline[*]}"
> 
> 
> Yao Yuan (1):
>   Makefile: Don't set -CFLAGS := in Makefile
> 
>  Makefile | 1 -
>  1 file changed, 1 deletion(-)
> 
> --
> 2.43.5
> 

Re: [PATCH kvmtool 0/1] Don't empty CFLAGS in Makefile for static building

[Yao Yuan]

On Mon, Aug 17, 2026 at 10:43:37AM +0800, Alexandru Elisei wrote:
> Hi,
>
> On Mon, Aug 17, 2026 at 04:45:33PM +0800, Yao Yuan wrote:
> > Don't set the CFLAGS to empty in Makefile for passing more
> > CFLAGS options from environment variable, e.g -static for
> > native static building.
>
> I think the lkvm-static makefile target might be your friend in this case :)
>
> $ make -j$(getconf _NPROCESSORS_ONLN) ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- lkvm-static
>
> (have a look at the $(PROGRAM)-static target if you want to double check that it
> fits your needs)

Hi Alex,

Thanks for such nice suggestion!

Yes, it fits my requirement and it works in native building yet.

So I think this can be dropped unless it helps in other purposes.

>
> Thanks,
> Alex
>
> >
> > One use case of static buidling is using kvmtool for
> > pre-silicon validation on emulation system, such system has
> > limited or even no IO part and run w/ small solo ramdisk as
> > linux userspace instead of full Linux distribution, and run
> > in slow speed. Thus the self-contained kvmtool static
> > building is good choice in performance and size for testing
> > on such system.
> >
> > The static building is verified on arm64 host:
> >
> > CFLAGS=-static make -j32
> > ...
> > LINK     lkvm
> > LN       vm
> >
> > $ldd ./lkvm
> >         not a dynamic executable
> >
> > The funciton is verified w/ below command, boot arm64 guest
> > to serial successfully:
> >
> > cmdline=(
> > 	ignore_loglevel
> > 	earlycon=uart8250,mmio,0x1000000,115200n8
> > 	console=uart8250,mmio,0x1000000,115200n8
> > 	nokaslr
> > 	selinux=0
> > 	audit=0
> > 	root=/dev/vda3
> > )
> >
> > ./lkvm run \
> > 	   --name test_kvmtool \
> > 	   -c 4 -m 1G \
> > 	   --nodefaults \
> > 	   --irqchip gicv3-its \
> > 	   --console serial \
> > 	   --virtio-transport pci \
> > 	   --disk /path/to/the/disk/image
> > 	   --kernel /path/to/the/arm64/boot/image
> > 	   --param "${cmdline[*]}"
> >
> >
> > Yao Yuan (1):
> >   Makefile: Don't set -CFLAGS := in Makefile
> >
> >  Makefile | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > --
> > 2.43.5
> >