From nobody Mon Feb 9 19:38:01 2026 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E373A192D68 for ; Mon, 25 Nov 2024 10:08:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732529317; cv=none; b=eAxRGJP8PH6kKmI/1f8PPUuaiuaFidcrlyxDKb4sy1euf/hrOldwCmWjWyQu/j1Fo0mv2Gbv+S4KHzp0ALkv4XjdYl/ANjUGD4I2hl1sDDSnLXlH88myBwivpcc321u/FhR1gS1f0yXVq9eQ3fi2w6ZtVUgINBxtVZ56lm+Mvq0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732529317; c=relaxed/simple; bh=+pmdgCkhVTXULc+zNZF3mqNKSLVfJPhAcX/3S8Yjupo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=doEymf78VG1bq9IdGP2TVsBa1bSG7zwOFiI3hptATq4JoMQMJ8lwB4iJWtw/iqknazSOWRT+1Oeg6fZRbJQcziToz6k/ix3/pJDJSzPHPgpEZot+p+0TIThvRIzS9+EDOQy3a4kyANpNWqmwJGGFHWwjbbi69yNpZXl7Nc1olP8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Hz9yRkL/; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Hz9yRkL/" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=1uC9ZsG8+iSDsihXzKgc5JDj2Gbt5KFaLk2mOsYAE18=; b=Hz9yRkL/51WZ+iQPTOfsXpI1M0 Io44/tFfv3HvNPTC30HtKctZcDnS9WF4bLtNX8jcHEPUnmYBRNaxz8Gd+ojnLpkUreLev8Vcufx5p nu84JTKFS8WrDq3dwgy2Ih4S6NeAGMJ6v4PbKgVsk8B39QwY0gEaW6bm3OodUKL43MGDZVGB9bGqX ZLx/uOI7aUY6U4yETF2fpw4h0Im15AGwaUD4RRMhIWtBxrEG/x4qD+fwG55uzwGw90ryXrDDh/gd2 zC7u/3um2egCEN/XYpCXFyDX6x+OBn6lOBvCBLeAwhHS4UUd4Uj6kIo/FEVvT5gothf5I5QteHh5/ qcXvO2+A==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tFW0z-0000000Bir9-441i; Mon, 25 Nov 2024 10:08:23 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tFW0z-000000000lQ-3Amp; Mon, 25 Nov 2024 10:08:21 +0000 From: David Woodhouse To: kexec@lists.infradead.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , David Woodhouse , "Kirill A. Shutemov" , Kai Huang , Nikolay Borisov , linux-kernel@vger.kernel.org, Simon Horman , Dave Young , Peter Zijlstra , jpoimboe@kernel.org, bsz@amazon.de Subject: [RFC PATCH v3 12/20] x86/kexec: Eliminate writes through kernel mapping of relocate_kernel page Date: Mon, 25 Nov 2024 09:54:42 +0000 Message-ID: <20241125100815.2512-13-dwmw2@infradead.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241125100815.2512-1-dwmw2@infradead.org> References: <20241125100815.2512-1-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Content-Type: text/plain; charset="utf-8" From: David Woodhouse All writes to the relocate_kernel control page are now done *after* the %cr3 switch via simple %rip-relative addressing, which means the DATA() macro with its pointer arithmetic can also now be removed. Signed-off-by: David Woodhouse --- arch/x86/kernel/relocate_kernel_64.S | 29 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocat= e_kernel_64.S index 16f123527406..288dfc08c63d 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -61,21 +61,24 @@ SYM_CODE_START_NOALIGN(relocate_kernel) pushq %r15 pushf =20 - movq %rsp, saved_rsp(%rip) - movq %cr0, %rax - movq %rax, saved_cr0(%rip) - movq %cr3, %rax - movq %rax, saved_cr3(%rip) - movq %cr4, %rax - movq %rax, saved_cr4(%rip) - - /* Save CR4. Required to enable the right paging mode later. */ - movq %rax, %r13 - /* zero out flags, and disable interrupts */ pushq $0 popfq =20 + /* Switch to the identity mapped page tables */ + movq %cr3, %rax + movq kexec_pa_table_page(%rip), %r9 + movq %r9, %cr3 + + /* Save %rsp and CRs. */ + movq %rsp, saved_rsp(%rip) + movq %rax, saved_cr3(%rip) + movq %cr0, %rax + movq %rax, saved_cr0(%rip) + /* Leave CR4 in %r13 to enable the right paging mode later. */ + movq %cr4, %r13 + movq %r13, saved_cr4(%rip) + /* Save SME active flag */ movq %r8, %r12 =20 @@ -85,10 +88,6 @@ SYM_CODE_START_NOALIGN(relocate_kernel) /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */ movq %rcx, %r11 =20 - /* Switch to the identity mapped page tables */ - movq kexec_pa_table_page(%rip), %r9 - movq %r9, %cr3 - /* Physical address of control page */ movq %rsi, %r8 =20 --=20 2.47.0