From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Amirmohammad Eftekhar <amirmohammad.eftekhar@cispa.de>,
Sashiko Bot <sashiko-bot@kernel.org>
Subject: [PATCH v3 19/21] KVM: selftests: Randomize L2's TSC offset in the nested TSC scaling test
Date: Wed, 30 Sep 2026 10:36:33 -0700 [thread overview]
Message-ID: <20260930173635.3362655-20-seanjc@google.com> (raw)
In-Reply-To: <20260930173635.3362655-1-seanjc@google.com>
Randomize L2's TSC offset in the nested TSC scaling test, not because it's
all that interesting, but because hardcoding a copmletely arbitrary value
is all kinds of silly.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../selftests/kvm/x86/nested_tsc_scaling_test.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c b/tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c
index 571fc214c925..be6246c20d7b 100644
--- a/tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c
+++ b/tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c
@@ -13,10 +13,9 @@
#include "svm_util.h"
#include "kselftest.h"
-/* L2's TSC multiplier, relative to L1. */
+/* L2's TSC multiplier and offset, relative to L1. */
static u64 l2_multiplier;
-
-#define TSC_OFFSET_L2 ((u64)-33125236320908)
+static u64 l2_offset;
enum { USLEEP, UCHECK_L1, UCHECK_L2 };
#define GUEST_SLEEP(sec) ucall(UCALL_SYNC, 2, USLEEP, sec)
@@ -75,7 +74,7 @@ static void l1_svm_code(struct svm_test_data *svm)
guest_check_tsc_freq(UCHECK_L1);
generic_svm_setup(svm, l2_guest_code);
- svm->vmcb->control.tsc_offset = TSC_OFFSET_L2;
+ svm->vmcb->control.tsc_offset = l2_offset;
/* enable TSC scaling for L2 */
wrmsr(MSR_AMD64_TSC_RATIO, l2_multiplier);
@@ -112,7 +111,7 @@ static void l1_vmx_code(struct vmx_pages *vmx_pages)
control |= SECONDARY_EXEC_TSC_SCALING;
vmwrite(SECONDARY_VM_EXEC_CONTROL, control);
- vmwrite(TSC_OFFSET, TSC_OFFSET_L2);
+ vmwrite(TSC_OFFSET, l2_offset);
vmwrite(TSC_MULTIPLIER, l2_multiplier);
/* launch L2 */
@@ -145,6 +144,9 @@ static void test_tsc_scaling(u64 l0_tsc_freq, u64 l1_tsc_freq, u64 l2_tsc_freq,
vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
+ l2_offset = kvm_random_u64(&kvm_rng);
+ sync_global_to_guest(vm, l2_offset);
+
l2_multiplier = __l2_multiplier;
sync_global_to_guest(vm, l2_multiplier);
--
2.56.0.rc1.315.gc6ed9934b7-goog
next prev parent reply other threads:[~2026-09-30 17:38 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-30 17:36 [PATCH v3 00/21] KVM: x86: Fix nested TSC scaling edge cases Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 01/21] KVM: x86: Saturate L2's TSC frequency if it exceeds hardware supports Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 02/21] KVM: SVM: Fallback to the default TSC ratio if KVM tries to use a bad multiplier Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 03/21] KVM: x86: Allow userspace to set KVM's max supported guest TSC frequency Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 04/21] KVM: selftests: Use KVM's pRNG to randomize L1's TSC ratio in TSC scaling test Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 05/21] KVM: selftests: Drop redundant VMWRITE of TSC_MULTIPLIER_HIGH Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 06/21] KVM: selftests: Drop unnecessary use of PRIu64 in nested TSC scaling test Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 07/21] KVM: selftests: Randomize L2's scale factor " Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 08/21] KVM: selftests: Rename TSC freq checkers " Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 09/21] KVM: selftests: Extract guts of nested TSC scaling test to helper function Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 10/21] KVM: selftests: Track L2 multiplier, not scale-up factor, in nested TSC test Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 11/21] KVM: selftests: Print out the failing L{0,1,2} level in nested TSC scaling test Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 12/21] KVM: selftests: Allow +/- 1 tolerance if expected TSC frequency is <100 Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 13/21] KVM: selftests: Use KVM's reported TSC KHz as L0's frequency (sanity checked) Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 14/21] KVM: selftests: Explicitly pass TSC frequencies to guts of TSC scaling test Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 15/21] KVM: selftests: Sanity check KVM's default TSC freq in nested " Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 16/21] KVM: selftests: Test L1 "up" and L2 "down" " Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 17/21] KVM: selftests: Verify that KVM saturates L2 TSC freq on {under,over}flow Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 18/21] KVM: selftests: Test non-zero TSC offset on SVM in nested TSC scaling test Sean Christopherson
2026-09-30 17:36 ` Sean Christopherson [this message]
2026-09-30 17:36 ` [PATCH v3 20/21] KVM: selftests: Use GUEST_SYNC2() " Sean Christopherson
2026-09-30 17:36 ` [PATCH v3 21/21] KVM: selftests: Spell out UCALL in nested TSC scaling test's enums Sean Christopherson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260930173635.3362655-20-seanjc@google.com \
--to=seanjc@google.com \
--cc=amirmohammad.eftekhar@cispa.de \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=sashiko-bot@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®