From: Dave Hansen <dave.hansen@intel.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
David Woodhouse <dwmw2@infradead.org>
Cc: "Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Eric Biederman" <ebiederm@xmission.com>,
"David Woodhouse" <dwmw@amazon.co.uk>,
"Sourabh Jain" <sourabhjain@linux.ibm.com>,
"Hari Bathini" <hbathini@linux.ibm.com>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Baoquan He" <bhe@redhat.com>, "Yuntao Wang" <ytcoode@gmail.com>,
"David Kaplan" <david.kaplan@amd.com>,
"Tao Liu" <ltao@redhat.com>, "Kai Huang" <kai.huang@intel.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Josh Poimboeuf" <jpoimboe@kernel.org>,
"Breno Leitao" <leitao@debian.org>,
"Wei Yang" <richard.weiyang@gmail.com>,
"Rong Xu" <xur@google.com>,
"Thomas Weißschuh" <thomas.weissschuh@linutronix.de>,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
"Simon Horman" <horms@kernel.org>,
"Dave Young" <dyoung@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
bsz@amazon.de, nathan@kernel.org
Subject: Re: [PATCH 1/9] x86/kexec: Disable global pages before writing to control page
Date: Tue, 17 Dec 2024 06:51:47 -0800 [thread overview]
Message-ID: <28a98c27-7307-4698-9182-35e0d2cf12ad@intel.com> (raw)
In-Reply-To: <tksesvqt266x6a6mnoi5aqa3fhsoyo7mbp277elrrft5eieoba@7ospdizq22y6>
On 12/17/24 04:25, Kirill A. Shutemov wrote:
>> Clear the PGE bit in %cr4 early, before storing data in the control page.
> It worth noting that flipping CR4.PGE triggers TLB flush. I was not sure
> if CR3 write is required to make it happen.
I thought about removing the CR3 write. But I decided against it because
CR4.PGE needs to actually change value, unlike CR3 writes where any
write can flush the TLB (modulo globals, PCID and bit 63 of course).
X86_FEATURE_PGE itself is required but I couldn't actually remember if
there are any cases where CR4.PGE==0. If there were, the CR3 write would
still be needed. I don't _think_ there are any ways forx86_64 to end up
with CR4.PGE==0, but I also wouldn't out the possibility that some silly
issue pops up making us play stupid games and win stupid prizes.
Anyway, I think we can leave the belt-and-suspenders programming in this
case. A comment wouldn't hurt I guess.
next prev parent reply other threads:[~2024-12-17 14:52 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-16 23:24 [PATCH 0/9] x86/kexec: Fixes for tip/x86/boot David Woodhouse
2024-12-16 23:24 ` [PATCH 1/9] x86/kexec: Disable global pages before writing to control page David Woodhouse
2024-12-17 12:25 ` Kirill A. Shutemov
2024-12-17 12:39 ` David Woodhouse
2024-12-17 14:51 ` Dave Hansen [this message]
2024-12-17 14:56 ` [EXTERNAL] " David Woodhouse
2024-12-17 15:06 ` Dave Hansen
2024-12-16 23:24 ` [PATCH 2/9] x86/kexec: Ensure preserve_context flag is set on return to kernel David Woodhouse
2024-12-17 16:38 ` Uros Bizjak
2025-01-03 10:14 ` David Woodhouse
2024-12-16 23:24 ` [PATCH 3/9] x86/kexec: Use correct swap page in swap_pages function David Woodhouse
2024-12-16 23:24 ` [PATCH 4/9] x86/kexec: Fix stack and handling of re-entry point for ::preserve_context David Woodhouse
2024-12-16 23:24 ` [PATCH 5/9] x86/kexec: Fix location of relocate_kernel with -ffunction-sections David Woodhouse
2024-12-16 23:24 ` [PATCH 6/9] x86/kexec: Mark machine_kexec() with __nocfi David Woodhouse
2024-12-16 23:24 ` [PATCH 7/9] kexec_core: Add and update comments regarding the KEXEC_JUMP flow David Woodhouse
2025-01-03 9:24 ` Dave Young
2025-01-03 10:14 ` David Woodhouse
2024-12-16 23:24 ` [PATCH 8/9] x86/kexec: Cope with relocate_kernel() not being at the start of the page David Woodhouse
2024-12-17 8:47 ` Ard Biesheuvel
2024-12-17 9:17 ` David Woodhouse
2024-12-17 9:25 ` Ard Biesheuvel
2024-12-17 9:36 ` David Woodhouse
2025-01-03 10:10 ` David Woodhouse
2025-01-06 16:09 ` Ard Biesheuvel
2025-01-06 16:13 ` David Woodhouse
2025-01-06 16:27 ` Ard Biesheuvel
2024-12-16 23:24 ` [PATCH 9/9] x86/kexec: Use typedef for relocate_kernel_fn function prototype David Woodhouse
2024-12-17 8:49 ` Ard Biesheuvel
2024-12-17 9:21 ` David Woodhouse
2024-12-17 9:29 ` Ard Biesheuvel
2024-12-17 9:42 ` David Woodhouse
2024-12-17 9:54 ` Ard Biesheuvel
2024-12-17 10:06 ` David Woodhouse
2024-12-17 10:14 ` Ard Biesheuvel
2024-12-17 10:47 ` David Woodhouse
2024-12-17 10:29 ` David Woodhouse
2024-12-26 8:38 ` [PATCH 0/9] x86/kexec: Fixes for tip/x86/boot David Woodhouse
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