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Mon, 02 Sep 2024 08:00:26 -0700 (PDT) From: Roger Pau Monne To: xen-devel@lists.xenproject.org Cc: Roger Pau Monne , Jan Beulich , Andrew Cooper Subject: [PATCH] x86/cpu: revert opt_allow_unsafe from __ro_after_init to __read_mostly Date: Mon, 2 Sep 2024 17:00:16 +0200 Message-ID: <20240902150016.63072-1-roger.pau@citrix.com> X-Mailer: git-send-email 2.46.0 MIME-Version: 1.0 Making opt_allow_unsafe read only after init requires changes to the logic in init_amd(), otherwise the following #PF happens on CPU hotplug: ----[ Xen-4.20.0-1-d x86_64 debug=y Tainted: H ]---- CPU: 1 RIP: e008:[] arch/x86/cpu/amd.c#init_amd+0x37f/0x993 [...] Xen call trace: [] R arch/x86/cpu/amd.c#init_amd+0x37f/0x993 [] F identify_cpu+0x2d4/0x4db [] F start_secondary+0x22e/0x3cf [] F __high_start+0x87/0xa0 Pagetable walk from ffff82d0404011ea: L4[0x105] = 000000006fc2e063 ffffffffffffffff L3[0x141] = 000000006fc2b063 ffffffffffffffff L2[0x002] = 000000807c7ca063 ffffffffffffffff L1[0x001] = 800000006f801121 ffffffffffffffff **************************************** Panic on CPU 1: FATAL PAGE FAULT [error_code=0003] Faulting linear address: ffff82d0404011ea **************************************** For the time being revert opt_allow_unsafe to be __read_mostly. Reported-by: Andrew Cooper Fixes: bfcb0abb191f ('types: replace remaining uses of s8') Signed-off-by: Roger Pau Monné Reviewed-by: Jan Beulich --- xen/arch/x86/cpu/amd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c index 903be14af4b9..7da04230393a 100644 --- a/xen/arch/x86/cpu/amd.c +++ b/xen/arch/x86/cpu/amd.c @@ -46,7 +46,7 @@ static unsigned int __initdata opt_cpuid_mask_thermal_ecx = ~0u; integer_param("cpuid_mask_thermal_ecx", opt_cpuid_mask_thermal_ecx); /* 1 = allow, 0 = don't allow guest creation, -1 = don't allow boot */ -int8_t __ro_after_init opt_allow_unsafe; +int8_t __read_mostly opt_allow_unsafe; boolean_param("allow_unsafe", opt_allow_unsafe); /* Signal whether the ACPI C1E quirk is required. */