[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 1/2] x86/pat: fix x86_has_pat_wp()
On 20.06.22 07:30, Juergen Gross wrote: > On 20.06.22 07:22, Thorsten Leemhuis wrote: >> On 14.06.22 17:09, Juergen Gross wrote: >>> On 03.05.22 15:22, Juergen Gross wrote: >>>> x86_has_pat_wp() is using a wrong test, as it relies on the normal >>>> PAT configuration used by the kernel. In case the PAT MSR has been >>>> setup by another entity (e.g. BIOS or Xen hypervisor) it might return >>>> false even if the PAT configuration is allowing WP mappings. >>>> >>>> Fixes: 1f6f655e01ad ("x86/mm: Add a x86_has_pat_wp() helper") >>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx> >>>> --- >>>> arch/x86/mm/init.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c >>>> index d8cfce221275..71e182ebced3 100644 >>>> --- a/arch/x86/mm/init.c >>>> +++ b/arch/x86/mm/init.c >>>> @@ -80,7 +80,8 @@ static uint8_t __pte2cachemode_tbl[8] = { >>>> /* Check that the write-protect PAT entry is set for >>>> write-protect */ >>>> bool x86_has_pat_wp(void) >>>> { >>>> - return __pte2cachemode_tbl[_PAGE_CACHE_MODE_WP] == >>>> _PAGE_CACHE_MODE_WP; >>>> + return >>>> __pte2cachemode_tbl[__cachemode2pte_tbl[_PAGE_CACHE_MODE_WP]] == >>>> + _PAGE_CACHE_MODE_WP; >>>> } >>>> enum page_cache_mode pgprot2cachemode(pgprot_t pgprot) >>> >>> x86 maintainers, please consider taking this patch, as it is fixing >>> a real bug. Patch 2 of this series can be dropped IMO. >> >> Juergen, can you help me out here please. Patch 2 afaics was supposed to >> fix this regression I'm tracking: >> https://lore.kernel.org/regressions/YnHK1Z3o99eMXsVK@mail-itl/ > No, patch 2 wasn't covering all needed cases. Ahh, happens. Thx for the info. >> Is Patch 1 alone enough to fix it? Or is there a different fix for it? > Patch 1 is fixing a different issue (it is lacking any maintainer > feedback, though). > > This patch of Jan should do the job, but it seems to be stuck, too: > https://lore.kernel.org/lkml/9385fa60-fa5d-f559-a137-6608408f88b0@xxxxxxxx/ Ahh. Fun fact: that was on my list of things to prod, too. >> Or is there some other solution to finally fix that regressions that >> ideally should have been fixed weeks ago already? > > I agree it should have been fixed quite some time now, but the x86 > maintainers don't seem to be interested in those stuck patches. :-( > > Maybe I should take a different approach: > > x86 maintainers, please speak up if you NAK (or Ack) any of above two > patches. > In case you don't NAK or take the patches, I'm inclined to carry them via > the Xen tree to get the issues fixed. Yeah, I'd be really glad if we could find a solution for this situation and get it finally fixed in mainline and backported to stable. Ciao, Thorsten
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