From nobody Tue Feb 10 00:38:51 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 25AD92036FF for ; Wed, 27 Nov 2024 19:04:09 +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=1732734251; cv=none; b=rLeKWwJglhjlU3JJmNF/SDuLmGCYlydYsSa6n16Q96sBbqUZ1SLbyE3GsBu4RolF0vwjwN9xI6Zdjcy1jKjIkowgOfiDzpWyQPh6TzmAtuW2F99AOF82whrqCxL4wW0VYaHqd8ec369rTx5AS+UwBO7xihMu2QgkBJgvAPeyvPo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732734251; c=relaxed/simple; bh=+pmdgCkhVTXULc+zNZF3mqNKSLVfJPhAcX/3S8Yjupo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fRywbbrCAflNlEoPC+Uw77d1uNdYTqb4lYWrLILBhqtrQDfsOOMiXH62LWRc+pzyD/RtYEPhskQf6Nc8cy7JwgQq7AnlGTeIkWOEV+umb2uB5hfFzudTT0TIINwohLIiH9ksdxYlZ/PUc9/pirJanWh66CVOvPg1JRrIgIuCqSI= 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=dE4JF530; 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="dE4JF530" 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=dE4JF530jNRnvReAd0VikcoJ8O bC33xLei1yRXs1wphmdArKG6YaNTh5gsBZqUnfD9WXzUAeZqNL5dfq+g9sv6jQ8KaaNBY6a9LFX5E Qw1i2KY8nyHUVFOdjzZSmsstOhpwYK8EquiRGjbLuel2Mlu32fA1G0HLiVe6643dwj26Up2k/sDU5 d6hVznEL8ZFAPCp8cKicl864rrc/VyHi1oXghgb2RhTo8IfP6T7VF3xbCR+os5aC8HwTvukBoHPJM TdMUWQ/fFGNGDBAfEc6EgDdtaWYlJCxmiUUfl3UQL/hvpIJ0Y/LvHzSrFisX/LaTxWFtKP6tvQshH 0TXP+OgQ==; 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 1tGNKD-00000001cWD-1fSS; Wed, 27 Nov 2024 19:03:46 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tGNKE-00000000Biu-1qv5; Wed, 27 Nov 2024 19:03:46 +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 v4 12/20] x86/kexec: Eliminate writes through kernel mapping of relocate_kernel page Date: Wed, 27 Nov 2024 19:00:26 +0000 Message-ID: <20241127190343.44916-13-dwmw2@infradead.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241127190343.44916-1-dwmw2@infradead.org> References: <20241127190343.44916-1-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