linux-kernel - Re: [patch V3 13/37] mips/mm/highmem: Switch to generic kmap atomic

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Date:   Sat, 9 Jan 2021 01:33:52 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     tglx@...utronix.de, airlied@...ux.ie, airlied@...hat.com,
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Subject: Re: [patch V3 13/37] mips/mm/highmem: Switch to generic kmap atomic

On Sat, Jan 09, 2021 at 12:58:05AM +0100, Thomas Bogendoerfer wrote:
> On Fri, Jan 08, 2021 at 08:20:43PM +0000, Paul Cercueil wrote:
> > Hi Thomas,
> > 
> > 5.11 does not boot anymore on Ingenic SoCs, I bisected it to this commit.
> > 
> > Any idea what could be happening?
> 
> not yet, kernel crash log of a Malta QEMU is below.

update:

This dirty hack lets the Malta QEMU boot again:

diff --git a/mm/highmem.c b/mm/highmem.c
index c3a9ea7875ef..190cdda1149d 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -515,7 +515,7 @@ void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 	BUG_ON(!pte_none(*(kmap_pte - idx)));
 	pteval = pfn_pte(pfn, prot);
-	set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval);
+	set_pte(kmap_pte - idx, pteval);
 	arch_kmap_local_post_map(vaddr, pteval);
 	current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
 	preempt_enable();

set_pte_at() tries to update cache and could do an kmap_atomic() there.
Not sure, if this is allowed at this point.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]