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[92.26.98.202]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac3147efb0csm260071866b.65.2025.03.14.11.33.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Mar 2025 11:33:50 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: e0a4b8ec-0102-11f0-9899-31a8f345e629 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1741977231; x=1742582031; darn=lists.xenproject.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=tHmDSBBFV7FBw7IEwYSqIeuIHgrmNgrKBbLTlCs3zHI=; b=W4tJc6UnIqf8DE4Up6o34w/+JIX6RvI7TiKWCc6fqHnxW6xuzdFYmIcy7jOXkfc/ar u3oD0/rnYpvKgI5wlqLx1GBGIRszFWNkTfdu/FMcleHqnuqJuLCk6wIptI9hv3EOdN/s vZ8pEen87VmHcwsuFcol/9ZVDfHPxu2y4B8lY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741977231; x=1742582031; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=tHmDSBBFV7FBw7IEwYSqIeuIHgrmNgrKBbLTlCs3zHI=; b=SW+wfjT++pwo1/+YPV6NWFJodXk93h08xz0mqAcdrmDTIOxDJyPtcIVwtKYqWq0gkA UhzeicyUjDHE9sbRBCP3HPRgjUTpgbxju7VhsY2YZEGCplJfCRK+RuO9sOkXAPhIOSVU OGkpLkHzSa2HtIeBWHhfRsPxGkxGYORyGx9V4p2aUcLtT0qagT93z0d2e3h6wIDI+Tes acGDtRbhlAOIKPmH9zy3vx9qQsg4BE7zfQ7uP1qvsRM+TDR/kSDBM1Io2V0G0KGxROZ+ zYZJvaq2hkVvfLH5EfInxU6zsnMFdyKeeBe4jqDalI2VnhSnjP4TMLsjKEN+/3YWtH37 8H1Q== X-Gm-Message-State: AOJu0YzSOsiQf8xYw2PZSkchUoZPyeS0babuStz+Y32XvAzaC7ewXEUD Ma+83Xspe4xTBNFQDYq1xfbdtJg6psn6MNFtWuBvH/zg+x51FySDjLvEUE/36Fl+PKZ1vR8sOAB T X-Gm-Gg: ASbGnctwiGkPgaf2HAahMXqgbRDAiwTpBcnXxFKNHqk/qcjzH0ruxT6Rvnf265O/C2/ zZliv8qqxiAF+bZMmIpY71oV0Xzhr36KPx4OIHk2egGJeALdEKzzEoO+WVK9Lm/95sI3Hi1I/M5 Ot7PXZyi9pmxhfq5WnBG6XnWatIfe1jLFd1Z7jYZ+KQsjDU0a7YoFAjW+dPUy2nAXMRy7WBjESj xT9asZSJ2+DPDCgBf7irURsGEsHAwzxu/OFnw/8b/Xm3YmLYxs80mrO5zkACDtwdbxhhtFNB57j Vx15o8ktBMqJWUPtaZ+rzh6rWbjy3zkgZMhwyEXpfCYqWPAiIfN0OKM1CI5CM32bwLTpd8pDqLF E2EgYvj5FBlOORh8s55ox6pR2 X-Google-Smtp-Source: AGHT+IFr5LV87pDfDV00iTKNTng4IRZ/DXvBGigFYQbOTKWfJNFrQZuqdr/4ND68uwqIoe07/2k/Pw== X-Received: by 2002:a17:907:c5cd:b0:abf:6d1c:8f4a with SMTP id a640c23a62f3a-ac3124b248bmr798303166b.18.1741977231250; Fri, 14 Mar 2025 11:33:51 -0700 (PDT) From: Andrew Cooper To: Xen-devel Cc: Andrew Cooper , Jan Beulich , =?utf-8?q?Roger_Pau_Monn=C3=A9?= Subject: [PATCH] x86/traps: Drop incorrect BUILD_BUG_ON() and comment in load_system_tables() Date: Fri, 14 Mar 2025 18:33:46 +0000 Message-Id: <20250314183346.77356-1-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 It is only the hardware task switching mechanism which cares about a TSS being at least 0x67 bytes long. Furthermore, since this check was added, the limit is now 0x6b if CET-SS is active. Nevertheless, task switches, being a relic of the 32-bit days, aren't relevant to Xen. LTR is is perfectly possible to load a shorter TSS, and indeed we will be doing so with FRED active. Signed-off-by: Andrew Cooper --- CC: Jan Beulich CC: Roger Pau Monné In principle this is Fixes: 788844062561 ("x86/xpti: Don't leak TSS-adjacent percpu data via Meltdown"), but I don't feel it's really a correct tag to give. --- xen/arch/x86/cpu/common.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c index e8d4ca3203be..698abb7086d8 100644 --- a/xen/arch/x86/cpu/common.c +++ b/xen/arch/x86/cpu/common.c @@ -900,8 +900,6 @@ void load_system_tables(void) wrmsrl(MSR_INTERRUPT_SSP_TABLE, (unsigned long)ist_ssp); } - BUILD_BUG_ON(sizeof(*tss) <= 0x67); /* Mandated by the architecture. */ - _set_tssldt_desc(gdt + TSS_ENTRY, (unsigned long)tss, sizeof(*tss) - 1, SYS_DESC_tss_avail); if ( IS_ENABLED(CONFIG_PV32) )