linux-kernel - Re: [tip:x86/boot] x86/boot/compressed/64: Prepare trampoline memory

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Date:   Sun, 25 Feb 2018 13:52:05 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Borislav Petkov <bp@...e.de>
Cc:     tglx@...utronix.de, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org, willy@...radead.org, hpa@...or.com,
        mingo@...nel.org, kirill.shutemov@...ux.intel.com,
        peterz@...radead.org, gorcunov@...nvz.org, luto@...capital.net,
        linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/boot] x86/boot/compressed/64: Prepare trampoline memory

On Sat, Feb 24, 2018 at 10:48:18PM +0100, Borislav Petkov wrote:
> On Sun, Feb 11, 2018 at 04:19:38AM -0800, tip-bot for Kirill A. Shutemov wrote:
> > Commit-ID:  b91993a87aff6dafd60a9c8ce80ebc425161a815
> > Gitweb:     https://git.kernel.org/tip/b91993a87aff6dafd60a9c8ce80ebc425161a815
> > Author:     Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > AuthorDate: Fri, 9 Feb 2018 17:22:27 +0300
> > Committer:  Ingo Molnar <mingo@...nel.org>
> > CommitDate: Sun, 11 Feb 2018 12:36:19 +0100
> > 
> > x86/boot/compressed/64: Prepare trampoline memory
> 
> This patch breaks X in my test guest image here. The failing Xorg.0.log file
> has:

Looks like the heuristic to finding right spot for trampoline fails. I
don't understand why.

Could you check if the patch below makes a difference?

If it is, could you check 0x9d000 address instead of 0x99000?

diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index dad5da7b4c1a..7274a02406a4 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -32,6 +32,7 @@ struct paging_config paging_prepare(void)
 			(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31))))
 		paging_config.l5_required = 1;
 
+#if 0
 	/*
 	 * Find a suitable spot for the trampoline.
 	 * This code is based on reserve_bios_regions().
@@ -49,6 +50,9 @@ struct paging_config paging_prepare(void)
 	/* Place the trampoline just below the end of low memory, aligned to 4k */
 	paging_config.trampoline_start = bios_start - TRAMPOLINE_32BIT_SIZE;
 	paging_config.trampoline_start = round_down(paging_config.trampoline_start, PAGE_SIZE);
+#else
+	paging_config.trampoline_start = 0x99000;
+#endif
 
 	trampoline = (unsigned long *)paging_config.trampoline_start;
 
-- 
 Kirill A. Shutemov