Re: [PATCH v4 kvmtool 00/12] arm64: Allow the user to set RAM base address

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 16/06/2022 14:48, Alexandru Elisei wrote:
> The series can be found at [1]. It is loosely based on the patches that
> allow the user to define the VM memory layout (RAM + MMIO) [2]. I've
> cherry-picked a handful of patches from that series, the rest I wrote from
> scratch since there have been several changes to the way guest memory is
> handled. I've chosen to focus on specifying the RAM layout with only one
> RAM bank and leave the rest for a later series because this was relatively
> easy to accomplish, while still being very useful.
> 
> What this series does: for arm64, the user can now specify the base address
> for RAM:
> 
> $ ./lkvm run -m1G@2G .. # Equivalent to ./lkvm run -m1024
> 
> The memory units are B (bytes), K (kilobytes), M (megabytes), G
> (gigabytes), T (terrabytes), P (petabytes). Lowercase is also valid.
> 
> Want to put RAM at the top of the physical address range? Easy:
> 
> $ ./lkvm run -m2G@1022G .. # Assumes the maximum is 40 bits of IPA
> 
> There one limitation on the RAM base address: it must not overlap with the
> MMIO range that kvmtool uses for arm/arm64, which lives below 2GB.
> 
> Why this is useful, in my opinion:
> 
> 1. Testing how a payload handles different memory layouts without the need
> to hack kvmtool or find the hardware that implements the desired layout.
> 
> 2. It can serve as a development tool for adding support for larger PA
> ranges for Linux and KVM (currently capped at 48 bits for 4k/16k pages), or
> other payloads.
> 
> Summary of the series
> ======================
> 
> * The series starts with refactoring how kvm->cfg.ram_size is validated
>    and used, followed by several cleanups in the arm and arm64 code.
> 
> * Then patch #8 ("builtin_run: Allow standard size specifiers for memory")
>    introduced the ability to specify the measurement unit for memory. I
>    believe that typing the equivalent of 2TB in megabytes isn't appealing
>    for anyone.
> 
> * More cleanups in the arm/arm64 code follow, which are needed for patch
>    #12 ("arm64: Allow the user to specify the RAM base address"). This is
>    where the ability to specify the RAM base address is introduced.
> 
> Testing
> =======
> 
> Same testing as before:
> 
> - Build tested each patch for all architectures.
> 
> - Ran an x86 kernel with and without setting the amount of RAM using the
>    memory specifiers; tested that setting the RAM address results in an
>    error.
> 
> - Ran an arm64 kernel without setting the size, with setting the size and
>    with setting the size and address; tried different addresses (2G, 3G,
>    256G); also tested that going below 2G or above the maximum IPA correctly
>    results in an error.
> 
> - Ran all arm64 kvm-unit-test tests with similar combinations of memory
>    size and address (instead of 256G I used 128G, as that's where I/O lives
>    for qemu and kvm-unit-tests maps that unconditionally as I/O).
> 
> - Ran all 32bit arm tests on an arm64 host with various combinations of
>    memory size and address (base address at 2G and 2.5G only due to a
>    limitation in the way the tests are set up).

I have tested this series on arm64 Fast model, with memory placed from
32bit to 48bit IPA and it works well.

For the series:

Reviewed-and-Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>

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