[kvm-unit-tests PATCH 0/3] x86: realmode: fixes

[kvm-unit-tests PATCH 0/3] x86: realmode: fixes

[Nadav Amit]

Some fixes for realmode tests.

Nadav Amit (3):
  x86: realmode: initialize idtr
  x86: realmode: hlt loop as fallback on exit
  x86: realmode: fix lss test

 x86/realmode.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

-- 
2.20.1

[kvm-unit-tests PATCH 1/3] x86: realmode: initialize idtr

[Nadav Amit]

The realmode test does not initialize the IDTR, assuming that its base
is zero and its limit 0x3ff. Initialize it, as the BIOS might not set it
as such.

Signed-off-by: Nadav Amit <namit@vmware.com>
---
 x86/realmode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/x86/realmode.c b/x86/realmode.c
index 234d607..ef79f7e 100644
--- a/x86/realmode.c
+++ b/x86/realmode.c
@@ -1799,6 +1799,7 @@ void realmode_start(void)
 unsigned long long r_gdt[] = { 0, 0x9b000000ffff, 0x93000000ffff };
 
 struct table_descr r_gdt_descr = { sizeof(r_gdt) - 1, &r_gdt };
+struct table_descr r_idt_descr = { 0x3ff, 0 };
 
 asm(
 	".section .init \n\t"
@@ -1819,6 +1820,7 @@ asm(
 	".text \n\t"
 	"start: \n\t"
 	"lgdt r_gdt_descr \n\t"
+	"lidt r_idt_descr \n\t"
 	"ljmp $8, $1f; 1: \n\t"
 	".code16gcc \n\t"
 	"mov $16, %eax \n\t"
-- 
2.20.1

[kvm-unit-tests PATCH 2/3] x86: realmode: hlt loop as fallback on exit

[Nadav Amit]

For systems without emulated devices (e.g., bare-metal), use halt-loop
when exiting the realmode test.

Signed-off-by: Nadav Amit <namit@vmware.com>
---
 x86/realmode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/x86/realmode.c b/x86/realmode.c
index ef79f7e..301b013 100644
--- a/x86/realmode.c
+++ b/x86/realmode.c
@@ -115,6 +115,10 @@ static int failed;
 static void exit(int code)
 {
 	outb(code, 0xf4);
+
+	while (1) {
+		asm volatile("hlt" ::: "memory");
+	}
 }
 
 struct regs {
-- 
2.20.1

[kvm-unit-tests PATCH 3/3] x86: realmode: fix lss test

[Nadav Amit]

Running lss with some random descriptor and then performing pop does not
work so well. Use mov instructions instead of push/pop pair.

Signed-off-by: Nadav Amit <namit@vmware.com>
---
 x86/realmode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/x86/realmode.c b/x86/realmode.c
index 301b013..90ecd13 100644
--- a/x86/realmode.c
+++ b/x86/realmode.c
@@ -1378,10 +1378,10 @@ static void test_lds_lss(void)
 		outregs.eax == (unsigned long)desc.address &&
 		outregs.ebx == desc.sel);
 
-	MK_INSN(lss, "pushl %ss\n\t"
+	MK_INSN(lss, "mov %ss, %dx\n\t"
 		     "lss (%ebx), %eax\n\t"
 		     "mov %ss, %ebx\n\t"
-		     "popl %ss\n\t");
+		     "mov %dx, %ss\n\t");
 	exec_in_big_real_mode(&insn_lss);
 	report("lss", R_AX | R_BX,
 		outregs.eax == (unsigned long)desc.address &&
-- 
2.20.1

Re: [kvm-unit-tests PATCH 1/3] x86: realmode: initialize idtr

[Paolo Bonzini]

On 26/06/20 11:23, Nadav Amit wrote:
> The realmode test does not initialize the IDTR, assuming that its base
> is zero and its limit 0x3ff. Initialize it, as the BIOS might not set it
> as such.

Rather the bootloader: realmode.flat is started as multiboot, that is in
a 32-bit protected mode environment---which includes an IDT.

Paolo

> Signed-off-by: Nadav Amit <namit@vmware.com>
> ---
>  x86/realmode.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/x86/realmode.c b/x86/realmode.c
> index 234d607..ef79f7e 100644
> --- a/x86/realmode.c
> +++ b/x86/realmode.c
> @@ -1799,6 +1799,7 @@ void realmode_start(void)
>  unsigned long long r_gdt[] = { 0, 0x9b000000ffff, 0x93000000ffff };
>  
>  struct table_descr r_gdt_descr = { sizeof(r_gdt) - 1, &r_gdt };
> +struct table_descr r_idt_descr = { 0x3ff, 0 };
>  
>  asm(
>  	".section .init \n\t"
> @@ -1819,6 +1820,7 @@ asm(
>  	".text \n\t"
>  	"start: \n\t"
>  	"lgdt r_gdt_descr \n\t"
> +	"lidt r_idt_descr \n\t"
>  	"ljmp $8, $1f; 1: \n\t"
>  	".code16gcc \n\t"
>  	"mov $16, %eax \n\t"
> 

Re: [kvm-unit-tests PATCH 0/3] x86: realmode: fixes

[Paolo Bonzini]

On 26/06/20 11:23, Nadav Amit wrote:
> Some fixes for realmode tests.
> 
> Nadav Amit (3):
>   x86: realmode: initialize idtr
>   x86: realmode: hlt loop as fallback on exit
>   x86: realmode: fix lss test
> 
>  x86/realmode.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 

Queued, thanks.

Paolo