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([2a02:6b6f:e750:1b00:1cfc:9209:4810:3ae5]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-475caf2eb9csm3367335e9.14.2025.10.22.15.25.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Oct 2025 15:25:40 -0700 (PDT) Message-ID: Date: Wed, 22 Oct 2025 23:25:39 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/3] x86: Fix kexec 5-level to 4-level paging transition Content-Language: en-GB To: dwmw@amazon.co.uk, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, ardb@kernel.org, hpa@zytor.com Cc: x86@kernel.org, apopple@nvidia.com, thuth@redhat.com, nik.borisov@suse.com, kas@kernel.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, kernel-team@meta.com, Michael van der Westhuizen , Tobias Fleig References: <20251022220755.1026144-1-usamaarif642@gmail.com> From: Usama Arif In-Reply-To: <20251022220755.1026144-1-usamaarif642@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 22/10/2025 23:06, Usama Arif wrote: > This series addresses critical bugs in the kexec path when transitioning > from a kernel using 5-level page tables to one using 4-level page tables. > > The root cause is improper handling of PGD entry value during the page level > transition. Specifically p4d value is masked with PAGE_MASK instead of > PTE_PFN_MASK, failing to account for high-order software bits like > _PAGE_BIT_NOPTISHADOW (bit 58). s/p4d value/PGD entry value/ for consistency.