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KVM: arm64: selftests: Add a userspace watchpoint test

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debug-exceptions covers guest self-hosted debug and userspace
single-step, but not a userspace (KVM_GUESTDBG_USE_HW) watchpoint,
whose KVM_EXIT_DEBUG reports the accessed address in debug.arch.far.
Add a test that installs a host-directed write watchpoint and checks
that the reported address matches the accessed variable.

Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260726143643.303456-3-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Fuad Tabba 2026-07-26 15:36:43 +01:00 committed by Oliver Upton
parent 119a9a23fb
commit 3be99f8751
1 changed files with 41 additions and 0 deletions
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41
tools/testing/selftests/kvm/arm64/debug-exceptions.c
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@ -527,6 +527,46 @@ void test_single_step_from_userspace(int test_cnt)
kvm_vm_free(vm);
}
static void guest_code_wp(void)
{
write_data = 'x';
GUEST_DONE();
}
/*
* A userspace hardware watchpoint (KVM_GUESTDBG_USE_HW) must fire and report
* the accessed address in debug.arch.far, exercising the watchpoint exit path.
*/
static void test_watchpoint_from_userspace(void)
{
struct kvm_guest_debug debug = {};
struct kvm_vcpu *vcpu;
struct kvm_run *run;
struct kvm_vm *vm;
vm = vm_create_with_one_vcpu(&vcpu, guest_code_wp);
run = vcpu->run;
debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW;
debug.arch.dbg_wcr[0] = DBGWCR_LEN8 | DBGWCR_RD | DBGWCR_WR |
DBGWCR_EL1 | DBGWCR_E;
/*
* BAS = 0xff (LEN8) requires a doubleword-aligned DBGWVR; FAR still
* reports the exact accessed byte.
*/
debug.arch.dbg_wvr[0] = PC(write_data) & ~7UL;
vcpu_guest_debug_set(vcpu, &debug);
vcpu_run(vcpu);
TEST_ASSERT(run->exit_reason == KVM_EXIT_DEBUG,
"Expected KVM_EXIT_DEBUG, got %u", run->exit_reason);
TEST_ASSERT((u64)run->debug.arch.far == PC(write_data),
"Watchpoint FAR 0x%lx != accessed address 0x%lx",
(u64)run->debug.arch.far, PC(write_data));
kvm_vm_free(vm);
}
/*
* Run debug testing using the various breakpoint#, watchpoint# and
* context-aware breakpoint# with the given ID_AA64DFR0_EL1 configuration.
@ -600,6 +640,7 @@ int main(int argc, char *argv[])
test_guest_debug_exceptions_all(aa64dfr0);
test_single_step_from_userspace(ss_iteration);
test_watchpoint_from_userspace();
return 0;
}