Re: [PATCH 02/20] KVM: selftests: Bump the minimum GPA for page tables to 0x200000

From: Sean Christopherson <seanjc@google.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Marc Zyngier <maz@kernel.org>, Oliver Upton <oupton@kernel.org>,
	 Paolo Bonzini <pbonzini@redhat.com>,
	Tianrui Zhao <zhaotianrui@loongson.cn>,
	 Bibo Mao <maobibo@loongson.cn>,
	Huacai Chen <chenhuacai@kernel.org>,
	 Anup Patel <anup@brainfault.org>, Paul Walmsley <pjw@kernel.org>,
	 Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	 Christian Borntraeger <borntraeger@linux.ibm.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	 Fuad Tabba <fuad.tabba@linux.dev>,
	Joey Gouly <joey.gouly@arm.com>,
	 Steffen Eiden <seiden@linux.ibm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	 Zenghui Yu <yuzenghui@huawei.com>,
	Atish Patra <atish.patra@linux.dev>,
	 Alexandre Ghiti <alex@ghiti.fr>,
	David Hildenbrand <david@kernel.org>,
	linux-arm-kernel@lists.infradead.org,  kvmarm@lists.linux.dev,
	kvm@vger.kernel.org, loongarch@lists.linux.dev,
	 kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
	 linux-kernel@vger.kernel.org,
	Nicholas Piggin <npiggin@gmail.com>,
	 Ritesh Harjani <ritesh.list@gmail.com>
Subject: Re: [PATCH 02/20] KVM: selftests: Bump the minimum GPA for page tables to 0x200000
Date: Fri, 28 Aug 2026 11:07:34 -0700	[thread overview]
Message-ID: <apHOZouaLKs5CgpI@google.com> (raw)
In-Reply-To: <20260828195848.2d14e9aa@p-imbrenda>

On Fri, Aug 28, 2026, Claudio Imbrenda wrote:
> On Wed, 26 Aug 2026 16:04:53 -0700
> Sean Christopherson <seanjc@google.com> wrote:
> 
> > Bump selftests completely arbitrary minimum GPA for page tables from
> > 0x180000 to 0x200000 (LoongArch's minimum), so that LoongArch can use
> > vm_alloc_page_table() instead of open coding a rough equivalent.
> > 
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > ---
> >  tools/testing/selftests/kvm/include/kvm_util.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> > index 5a7a455b5387..70906a0d1003 100644
> > --- a/tools/testing/selftests/kvm/include/kvm_util.h
> > +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> > @@ -175,7 +175,7 @@ static inline struct userspace_mem_region *vm_get_mem_region(struct kvm_vm *vm,
> >  
> >  /* Minimum allocated guest virtual and physical addresses */
> >  #define KVM_UTIL_MIN_VADDR		0x2000
> > -#define KVM_GUEST_PAGE_TABLE_MIN_PADDR	0x180000
> > +#define KVM_GUEST_PAGE_TABLE_MIN_PADDR	0x200000
> >  
> >  #define DEFAULT_GUEST_STACK_VADDR_MIN	0xab6000
> >  #define DEFAULT_STACK_PGS		5
> 
> this breaks s390/cmma_test
> 
> I tried a quick fix, but nope... I will need to actually invest some
> time (i.e. next week) to understand why the quick fix is not enough,
> and come up with a proper fix
> 
> the good news is: it seems like cmma_test is the only test that is
> negatively affected by this series.

Is it this change specifically that's problematic?  Because if so, you can probably
just do nothing, because Sashiko (argh, just remembered that Sashiko doesn't Cc
everyone) pointed out that this will likely break some arm64 tests as well[*].

The LoongArch folks confirmed that using KVM_GUEST_PAGE_TABLE_MIN_PADDR as-is
should be a-ok, so my plan is to drop this patch and instead have LoongArch use
KVM_GUEST_PAGE_TABLE_MIN_PADDR.  I.e. make LoongArch match everyone else, instead
of making everyone else match LoongArch.

[*] https://lore.kernel.org/all/20260826232224.782021F000E9@smtp.kernel.org

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