From: Oliver Upton <oliver.upton@linux.dev>
To: Sean Christopherson <seanjc@google.com>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Shuah Khan <shuah@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
kvmarm@lists.linux.dev, Ricardo Koller <ricarkol@google.com>,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] KVM: arm64: selftests: Align VA space allocator with TTBR0
Date: Thu, 8 Dec 2022 00:27:02 +0000 [thread overview]
Message-ID: <Y5EvVtAoDSHvIKie@google.com> (raw)
In-Reply-To: <Y5EtP5z6rxSK1VUe@google.com>
On Thu, Dec 08, 2022 at 12:18:07AM +0000, Sean Christopherson wrote:
[...]
> Together, what about? The #ifdef is a bit gross, especially around "hi_start",
> but it's less duplicate code. And IMO, having things bundled in the same place
> makes it a lot easier for newbies (to arm64 or kernel coding in general) to
> understand what's going on and why arm64 is different.
I'd rather we not go this route. We really shouldn't make any attempt to
de-dupe something that is inherently architecture specific.
For example:
> + /*
> + * All architectures supports splitting the virtual address space into
> + * a high and a low half. Populate both halves, except for arm64 which
> + * currently uses only TTBR0_EL1 (arbitrary selftests "logic"), i.e.
> + * only has a valid low half.
> + */
> + sparsebit_num_t nr_va_bits = (1ULL << (vm->va_bits - 1)) >> vm->page_shift;
This is still wrong for arm64. When we say the VA space is 48 bits, we
really do mean that TTBR0 is able to address a full 48 bits. So this
truncates the MSB for the addressing mode.
With the code living in the arm64 side of the shop, I can also tailor
the comment to directly match the architecture to provide breadcrumbs
tying it back to the Arm ARM.
--
Thanks,
Oliver
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next prev parent reply other threads:[~2022-12-08 0:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-07 21:48 [PATCH 0/4] KVM: selftests: Fixes for ucall pool + page_fault_test Oliver Upton
2022-12-07 21:48 ` [PATCH 1/4] KVM: selftests: Fix build due to ucall_uninit() removal Oliver Upton
2022-12-07 21:48 ` [PATCH 2/4] KVM: selftests: Setup ucall after loading program into guest memory Oliver Upton
2022-12-07 23:57 ` Sean Christopherson
2022-12-08 0:17 ` Oliver Upton
2022-12-08 0:24 ` Sean Christopherson
2022-12-08 0:37 ` Oliver Upton
2022-12-08 18:47 ` Ricardo Koller
2022-12-08 19:01 ` Sean Christopherson
2022-12-08 19:49 ` Ricardo Koller
2022-12-09 1:08 ` Sean Christopherson
2022-12-07 21:48 ` [PATCH 3/4] KVM: arm64: selftests: Align VA space allocator with TTBR0 Oliver Upton
2022-12-08 0:18 ` Sean Christopherson
2022-12-08 0:27 ` Oliver Upton [this message]
2022-12-08 1:09 ` Sean Christopherson
2022-12-08 16:23 ` Andrew Jones
2022-12-07 21:48 ` [PATCH 4/4] KVM: selftests: Allocate ucall pool from MEM_REGION_DATA Oliver Upton
2022-12-07 23:44 ` Sean Christopherson
2022-12-07 23:56 ` Oliver Upton
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