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Date: Wed, 12 Feb 2020 17:40:37 +0100 From: Paolo Bonzini <pbonzini@...hat.com> To: Paul Burton <paulburton@...nel.org>, Mike Rapoport <rppt@...ux.ibm.com> Cc: Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, Sean Christopherson <sean.j.christopherson@...el.com>, linux-mips@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com> Subject: Re: [PATCH RFC 0/4] KVM: MIPS: Provide arch-specific kvm_flush_remote_tlbs() On 12/02/20 17:30, Paul Burton wrote: > Hi Paolo, > > On Wed, Feb 12, 2020 at 01:25:30PM +0100, Paolo Bonzini wrote: >> MIPS folks, I see that arch/mips/kvm/mmu.c uses pud_index, so it's not >> clear to me if it's meant to only work if CONFIG_PGTABLE_LEVELS=4 or >> it's just bit rot. Should I add a "depends on PGTABLE_LEVEL=4" to >> arch/mips/Kconfig? > > I'm no expert on this bit of code, but I'm pretty sure the systems > KVM/VZ has been used on the most internally had PGTABLE_LEVEL=3. > > I suspect this is actually a regression from commit 31168f033e37 ("mips: > drop __pXd_offset() macros that duplicate pXd_index() ones"). Whilst > that commit is correct that pud_index() & __pud_offset() are the same > when pud_index() is actually provided, it doesn't take into account the > __PAGETABLE_PUD_FOLDED case. There __pud_offset() was available but > would always evaluate to zero, whereas pud_index() isn't defined... Ok, I'll try to whip out a patch that handles __PAGETABLE_PUD_FOLDED. On the other hand this makes me worry about how much KVM is being tested by people that care about MIPS (even just compile-tested). Paolo
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