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e0ccc45b05
Until recently, the kernel could unexpectedly discard SVE state for a
period after a KVM_RUN ioctl, when the guest did not execute any
FPSIMD/SVE/SME instructions. We fixed that issue in commit:
fbc7e61195 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state")
Add a test which tries to provoke that issue by manipulating SVE state
before/after running a guest which does not execute any FPSIMD/SVE/SME
instructions. The test executes a handful of iterations to miminize
the risk that the issue is masked by preemption.
Signed-off--by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20250417-kvm-selftest-sve-signal-v1-1-6330c2f3da0c@kernel.org
[maz: Restored MR's SoB, fixed commit message according to MR's write-up]
Signed-off-by: Marc Zyngier <maz@kernel.org>
127 lines
2.2 KiB
C
127 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Host SVE: Check FPSIMD/SVE/SME save/restore over KVM_RUN ioctls.
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*
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* Copyright 2025 Arm, Ltd
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*/
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#include <errno.h>
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#include <signal.h>
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#include <sys/auxv.h>
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#include <asm/kvm.h>
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#include <kvm_util.h>
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#include "ucall_common.h"
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static void guest_code(void)
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{
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for (int i = 0; i < 10; i++) {
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GUEST_UCALL_NONE();
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}
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GUEST_DONE();
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}
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void handle_sigill(int sig, siginfo_t *info, void *ctx)
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{
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ucontext_t *uctx = ctx;
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printf(" < host signal %d >\n", sig);
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/*
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* Skip the UDF
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*/
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uctx->uc_mcontext.pc += 4;
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}
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void register_sigill_handler(void)
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{
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struct sigaction sa = {
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.sa_sigaction = handle_sigill,
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.sa_flags = SA_SIGINFO,
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};
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sigaction(SIGILL, &sa, NULL);
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}
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static void do_sve_roundtrip(void)
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{
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unsigned long before, after;
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/*
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* Set all bits in a predicate register, force a save/restore via a
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* SIGILL (which handle_sigill() will recover from), then report
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* whether the value has changed.
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*/
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asm volatile(
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" .arch_extension sve\n"
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" ptrue p0.B\n"
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" cntp %[before], p0, p0.B\n"
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" udf #0\n"
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" cntp %[after], p0, p0.B\n"
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: [before] "=r" (before),
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[after] "=r" (after)
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:
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: "p0"
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);
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if (before != after) {
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TEST_FAIL("Signal roundtrip discarded predicate bits (%ld => %ld)\n",
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before, after);
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} else {
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printf("Signal roundtrip preserved predicate bits (%ld => %ld)\n",
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before, after);
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}
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}
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static void test_run(void)
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{
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struct kvm_vcpu *vcpu;
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struct kvm_vm *vm;
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struct ucall uc;
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bool guest_done = false;
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register_sigill_handler();
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vm = vm_create_with_one_vcpu(&vcpu, guest_code);
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do_sve_roundtrip();
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while (!guest_done) {
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printf("Running VCPU...\n");
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vcpu_run(vcpu);
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switch (get_ucall(vcpu, &uc)) {
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case UCALL_NONE:
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do_sve_roundtrip();
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do_sve_roundtrip();
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break;
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case UCALL_DONE:
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guest_done = true;
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break;
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case UCALL_ABORT:
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REPORT_GUEST_ASSERT(uc);
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break;
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default:
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TEST_FAIL("Unexpected guest exit");
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}
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}
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kvm_vm_free(vm);
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}
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int main(void)
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{
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/*
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* This is testing the host environment, we don't care about
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* guest SVE support.
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*/
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if (!(getauxval(AT_HWCAP) & HWCAP_SVE)) {
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printf("SVE not supported\n");
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return KSFT_SKIP;
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}
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test_run();
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return 0;
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}
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