Hi Oliver,
On Tue, 02 Nov 2021 09:46:51 +0000,
Oliver Upton <oupton@xxxxxxxxxx> wrote:
>
> KVM now correctly handles the OS Lock for its guests. When set, KVM
> blocks all debug exceptions originating from the guest. Add test cases
> to the debug-exceptions test to assert that software breakpoint,
> hardware breakpoint, watchpoint, and single-step exceptions are in fact
> blocked.
>
> Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
> ---
> .../selftests/kvm/aarch64/debug-exceptions.c | 58 ++++++++++++++++++-
> 1 file changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
> index e5e6c92b60da..6b6ff81cdd23 100644
> --- a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
> +++ b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
> @@ -23,7 +23,7 @@
> #define SPSR_D (1 << 9)
> #define SPSR_SS (1 << 21)
>
> -extern unsigned char sw_bp, hw_bp, bp_svc, bp_brk, hw_wp, ss_start;
> +extern unsigned char sw_bp, hw_bp, hw_bp2, bp_svc, bp_brk, hw_wp, ss_start;
> static volatile uint64_t sw_bp_addr, hw_bp_addr;
> static volatile uint64_t wp_addr, wp_data_addr;
> static volatile uint64_t svc_addr;
> @@ -47,6 +47,14 @@ static void reset_debug_state(void)
> isb();
> }
>
> +static void enable_os_lock(void)
> +{
> + write_sysreg(oslar_el1, 1);
> + isb();
> +
> + GUEST_ASSERT(read_sysreg(oslsr_el1) & 2);
> +}
> +
> static void install_wp(uint64_t addr)
> {
> uint32_t wcr;
> @@ -99,6 +107,7 @@ static void guest_code(void)
> GUEST_SYNC(0);
>
> /* Software-breakpoint */
> + reset_debug_state();
> asm volatile("sw_bp: brk #0");
> GUEST_ASSERT_EQ(sw_bp_addr, PC(sw_bp));
>
> @@ -152,6 +161,51 @@ static void guest_code(void)
> GUEST_ASSERT_EQ(ss_addr[1], PC(ss_start) + 4);
> GUEST_ASSERT_EQ(ss_addr[2], PC(ss_start) + 8);
>
> + GUEST_SYNC(6);
> +
> + /* OS Lock blocking software-breakpoint */
> + reset_debug_state();
> + enable_os_lock();
> + sw_bp_addr = 0;
> + asm volatile("brk #0");
> + GUEST_ASSERT_EQ(sw_bp_addr, 0);
I haven't had a change to properly review the series, but this one
definitely caught my eye. My expectations are that BRK is *not*
affected by the OS Lock. The ARMv8 ARM goes as far as saying:
<quote>
Breakpoint Instruction exceptions are enabled regardless of the state
of the OS Lock and the OS Double Lock.
</quote>
as well as:
<quote>
There is no enable control for Breakpoint Instruction exceptions. They
are always enabled, and cannot be masked.
</quote>
I wonder how your test succeeds, though.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
