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[195.38.112.2]) by smtp.gmail.com with ESMTPSA id x18-20020adfffd2000000b0034181bea3b0sm6554504wrs.3.2024.03.24.03.31.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 24 Mar 2024 03:31:41 -0700 (PDT) Sender: Ingo Molnar Date: Sun, 24 Mar 2024 11:31:39 +0100 From: Ingo Molnar To: Steve Wahl Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Linux regressions mailing list , Pavin Joseph , stable@vger.kernel.org, Eric Hagberg , Simon Horman , Eric Biederman , Dave Young , Sarah Brofeldt , Russ Anderson , Dimitri Sivanich Subject: Re: [PATCH] x86/mm/ident_map: Use full gbpages in identity maps except on UV platform. Message-ID: References: <20240322162135.3984233-1-steve.wahl@hpe.com> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240322162135.3984233-1-steve.wahl@hpe.com> * Steve Wahl wrote: > Some systems have ACPI tables that don't include everything that needs > to be mapped for a successful kexec. These systems rely on identity > maps that include the full gigabyte surrounding any smaller region > requested for kexec success. Without this, they fail to kexec and end > up doing a full firmware reboot. > > So, reduce the use of GB pages only on systems where this is known to > be necessary (specifically, UV systems). > > Signed-off-by: Steve Wahl > Fixes: d794734c9bbf ("x86/mm/ident_map: Use gbpages only where full GB page should be mapped.") > Reported-by: Pavin Joseph Sigh, why was d794734c9bbf marked for a -stable backport? The commit never explains ... If it's broken, it should be reverted - instead of trying to partially revert and then maybe break some other systems. When there's boot breakage with new patches, we back out the bad patch and re-try in 99.9% of the cases. Thanks, Ingo