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[109.220.140.180]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46667221de7sm34853939f8f.33.2026.06.23.06.37.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2026 06:37:26 -0700 (PDT) From: Guillaume Ranquet X-Google-Original-From: Guillaume Ranquet Date: Tue, 23 Jun 2026 15:37:14 +0200 Subject: [PATCH RFC] x86/xen/pvh: Disable KASAN in early pvh boot stages Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260623-xen_kasan-v1-1-d963df2233d7@missingno.tech> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDMyNj3YrUvPjsxOLEPF1TU3PDRGOLNKMk01QloPqCotS0zAqwWdFKQW7 OSrG1tQBAogg0YAAAAA== X-Change-ID: 20260623-xen_kasan-5571a38f2b5e To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Juergen Gross , Boris Ostrovsky , Stefano Stabellini , Oleksandr Tyshchenko Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Guillaume Ranquet X-Mailer: b4 0.14.3 Running a xen pvh guest under KASAN results in a triple fault as the KASAN shadow region is not initialized this early in the boot flow. (XEN) [ 2.018691] d0v0 Triple fault - invoking HVM shutdown action 1 (XEN) [ 2.018693] *** Dumping Dom0 vcpu#0 state: *** (XEN) [ 2.018695] ----[ Xen-4.20.1-pre x86_64 debug=3Dn Not tainted ]---- (XEN) [ 2.018697] CPU: 0 (XEN) [ 2.018698] RIP: 0008:[] (XEN) [ 2.018698] RFLAGS: 0000000000000006 CONTEXT: hvm guest (d0v0) (XEN) [ 2.018700] rax: dffffc00072775d7 rbx: 00000000072775d7 rcx: 00000000= 00000000 (XEN) [ 2.018702] rdx: ffffffff843b56c0 rsi: 00000000336ec578 rdi: ffffffff= 8368c1ec (XEN) [ 2.018703] rbp: 00000000393baff0 rsp: 00000000393baeb8 r8: 000000003= 93bb000 (XEN) [ 2.018704] r9: 00000000393bb00c r10: 0000000000000000 r11: 000000000= 0000000 (XEN) [ 2.018706] r12: ffffffff843b56c0 r13: 00000000393bb008 r14: 00000000= 393bb000 (XEN) [ 2.018707] r15: 0000000040000000 cr0: 0000000080000011 cr4: 00000000= 00000020 (XEN) [ 2.018708] cr3: 00000000393bc000 cr2: 0000000000000000 (XEN) [ 2.018709] fsb: 0000000000000000 gsb: 00000000393b7020 gss: 00000000= 00000000 (XEN) [ 2.018711] ds: 0010 es: 0010 fs: 0000 gs: 0000 ss: 0010 cs: 0008 (XEN) [ 2.018712] Hardware Dom0 shutdown: rebooting machine (XEN) [ 2.180946] Resetting with ACPI MEMORY or I/O RESET_REG. Signed-off-by: Guillaume Ranquet --- The KASAN shadow region is not initialized this early in the boot stage, so disable instrumentation of the early boot. Though I'm wondering if disabling KASAN for `arch/x86/kernel/cpu/common.c` = is the right move. There's a single call to `get_cpu_vendor()` from `arch/x86/xen/enlighten.c`. I haven't looked if there's a solution to avoid disabling KASAN for everyone in `common.c`. Opinions welcome? Also note that I haven't tested HVM/PV or PVHVM. --- arch/x86/kernel/cpu/Makefile | 2 ++ arch/x86/xen/Makefile | 4 ++++ drivers/xen/Makefile | 2 ++ 3 files changed, 8 insertions(+) diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile index d2e8a849f180..8d1d45c231bc 100644 --- a/arch/x86/kernel/cpu/Makefile +++ b/arch/x86/kernel/cpu/Makefile @@ -17,6 +17,8 @@ KMSAN_SANITIZE_common.o :=3D n # As above, instrumenting secondary CPU boot code causes boot hangs. KCSAN_SANITIZE_common.o :=3D n =20 +KASAN_SANITIZE_common.o :=3D n + obj-y :=3D cacheinfo.o scattered.o obj-y +=3D topology_common.o topology_ext.o topology_amd.o obj-y +=3D cpuid_parser.o diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile index 717264ae269b..940284eb9835 100644 --- a/arch/x86/xen/Makefile +++ b/arch/x86/xen/Makefile @@ -7,6 +7,10 @@ CFLAGS_REMOVE_time.o =3D -pg CFLAGS_REMOVE_irq.o =3D -pg endif =20 +KASAN_SANITIZE_enlighten_pvh.o :=3D n +KASAN_SANITIZE_enlighten.o :=3D n +KASAN_SANITIZE_efi.o :=3D n + # Make sure early boot has no stackprotector CFLAGS_enlighten_pv.o :=3D -fno-stack-protector CFLAGS_mmu_pv.o :=3D -fno-stack-protector diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index c0503f1c7d5b..d71742c382dd 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -5,6 +5,8 @@ obj-y +=3D mem-reservation.o obj-y +=3D events/ obj-y +=3D xenbus/ =20 +KASAN_SANITIZE_efi.o :=3D n + CFLAGS_features.o :=3D -fno-stack-protector =20 dom0-$(CONFIG_ARM64) +=3D arm-device.o --- base-commit: 4e5dfb7c84012007c3c7061126491bbc92d71bf1 change-id: 20260623-xen_kasan-5571a38f2b5e Best regards, --=20 Guillaume Ranquet