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Tue, 22 Oct 2024 15:39:58 -0700 (PDT) From: Andrew Cooper To: Xen-devel Cc: Andrew Cooper , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , "Daniel P . Smith" Subject: [PATCH 1/3] x86/boot: Convert move_memory() to use bootstrap_map_addr() Date: Tue, 22 Oct 2024 23:39:52 +0100 Message-Id: <20241022223954.432554-2-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20241022223954.432554-1-andrew.cooper3@citrix.com> References: <20241022223954.432554-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1729636837833116600 move_memory() is very complicated, and buggy. In order to fix the latter, = we have to address the former. Given prior cleanup, bootstrap_map() is now implemented in terms of bootstrap_map_addr(), meaining that it is counterproductive to plumb the mapping through module_t. Delete mod, and introduce two same-sized/named fields. At this point in bo= ot, neither fields have their named purpose, so indicate the purpose in comment= s. No functional change. Signed-off-by: Andrew Cooper Reviewed-by: Daniel P. Smith --- CC: Jan Beulich CC: Roger Pau Monn=C3=A9 CC: Daniel P. Smith This is broken out both to ease review (I recommend git diff --color-words), and for bisection purposes given how many times I've failed to edit this lo= gic correctly. This does not conflict with anything in Hyperlaunch v7, but it does remove = the only callers of bootstrap_map() remaining by the end of the series, allowing for even more cleanup. In terms of bugs. The ones I've spotted so far are: * The blksz calculation depends on the previous thing having been unmapped first. * The calculation halving blksz based on BOOTSTRAP_MAP_BASE is bogus. It might plausibly be a remnent of 32bit Xen with the absence of highmem. * The caller of move_memory() is strictly moving modules forward in memory (dst > src) with a possibility of partial overlap. The while loop maps dst and src, blksz chunks at a time, ascending, with s < d. This results in memmove() doing an unconditional backwards copy. I don't see how this logic could ever have worked for an overlapping mov= e. * The caller of move_memory() already has a good mapping for dst, so we do= n't even need to split BOOTSTRAP_MAP_LIMIT in half to map both parts. --- xen/arch/x86/setup.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c index 059b597331a7..46a0b3093c2c 100644 --- a/xen/arch/x86/setup.c +++ b/xen/arch/x86/setup.c @@ -492,26 +492,29 @@ static void __init noinline move_memory( =20 while ( size ) { - module_t mod; + unsigned int start /* frame */; + unsigned int end /* mapsz */; unsigned int soffs =3D src & mask; unsigned int doffs =3D dst & mask; unsigned int sz; void *d, *s; =20 - mod.mod_start =3D (src - soffs) >> PAGE_SHIFT; - mod.mod_end =3D soffs + size; - if ( mod.mod_end > blksz ) - mod.mod_end =3D blksz; - sz =3D mod.mod_end - soffs; - s =3D bootstrap_map(&mod); - - mod.mod_start =3D (dst - doffs) >> PAGE_SHIFT; - mod.mod_end =3D doffs + size; - if ( mod.mod_end > blksz ) - mod.mod_end =3D blksz; - if ( sz > mod.mod_end - doffs ) - sz =3D mod.mod_end - doffs; - d =3D bootstrap_map(&mod); + start =3D (src - soffs) >> PAGE_SHIFT; + end =3D soffs + size; + if ( end > blksz ) + end =3D blksz; + sz =3D end - soffs; + s =3D bootstrap_map_addr(pfn_to_paddr(start), + pfn_to_paddr(start) + end); + + start =3D (dst - doffs) >> PAGE_SHIFT; + end =3D doffs + size; + if ( end > blksz ) + end =3D blksz; + if ( sz > end - doffs ) + sz =3D end - doffs; + d =3D bootstrap_map_addr(pfn_to_paddr(start), + pfn_to_paddr(start) + end); =20 memmove(d + doffs, s + soffs, sz); =20 @@ -519,7 +522,7 @@ static void __init noinline move_memory( src +=3D sz; size -=3D sz; =20 - bootstrap_map(NULL); + bootstrap_map_addr(0, 0); } } =20 --=20 2.39.5