From: Richard Henderson <richard.henderson@linaro.org>
To: "Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"Peter Maydell" <peter.maydell@linaro.org>
Cc: "Aleksandar Rikalo" <aleksandar.rikalo@syrmia.com>,
"David Hildenbrand" <david@redhat.com>,
"Cornelia Huck" <cohuck@redhat.com>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Beniamino Galvani" <b.galvani@gmail.com>,
qemu-s390x <qemu-s390x@nongnu.org>,
qemu-arm <qemu-arm@nongnu.org>,
"Hervé Poussineau" <hpoussin@reactos.org>,
"Gerd Hoffmann" <kraxel@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Richard Henderson" <rth@twiddle.net>
Subject: Re: [PATCH 5/6] exec: Restrict 32-bit CPUs to 32-bit address space
Date: Mon, 1 Jun 2020 17:01:52 -0700 [thread overview]
Message-ID: <eddd2573-84cc-dcd3-09b0-85c6ba989721@linaro.org> (raw)
In-Reply-To: <2e78619d-543b-55b7-f241-7652274fcf4a@amsat.org>
On 6/1/20 1:09 AM, Philippe Mathieu-Daudé wrote:
> On 5/31/20 9:09 PM, Peter Maydell wrote:
>> On Sun, 31 May 2020 at 18:54, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>>>
>>> It is pointless to have 32-bit CPUs see a 64-bit address
>>> space, when they can only address the 32 lower bits.
>>>
>>> Only create CPU address space with a size it can address.
>>> This makes HMP 'info mtree' command easier to understand
>>> (on 32-bit CPUs).
>>
>>> diff --git a/exec.c b/exec.c
>>> index 5162f0d12f..d6809a9447 100644
>>> --- a/exec.c
>>> +++ b/exec.c
>>> @@ -2962,9 +2962,17 @@ static void tcg_commit(MemoryListener *listener)
>>>
>>> static void memory_map_init(void)
>>> {
>>> + uint64_t system_memory_size;
>>> +
>>> +#if TARGET_LONG_BITS >= 64
>>> + system_memory_size = UINT64_MAX;
>>> +#else
>>> + system_memory_size = 1ULL << TARGET_LONG_BITS;
>>> +#endif
>>
>> TARGET_LONG_BITS is a description of the CPU's virtual
>> address size; but the size of the system_memory memory
>> region is related to the CPU's physical address size[*].
>
> OK I misunderstood it was the physical size, not virtual.
It is the physical size.
In the armv7 case, the lpae page table entry maps a 32-bit virtual address to a
40-bit physical address. The i686 page table extensions do something similar.
See TARGET_PHYS_ADDR_SPACE_BITS.
r~
next prev parent reply other threads:[~2020-06-02 0:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-31 17:54 [PATCH 0/6] exec/memory: Rework some address and access size limits Philippe Mathieu-Daudé
2020-05-31 17:54 ` [PATCH 1/6] target/s390x/mmu_helper: Use address_space_rw() in place Philippe Mathieu-Daudé
2020-06-02 7:11 ` David Hildenbrand
2020-05-31 17:54 ` [PATCH 2/6] hw/dma/rc4030: Use DMA address space to do DMA accesses Philippe Mathieu-Daudé
2020-05-31 17:54 ` [PATCH 3/6] hw/sd/allwinner-sdhost: Do DMA accesses via DMA address space Philippe Mathieu-Daudé
2020-05-31 19:31 ` Philippe Mathieu-Daudé
2020-05-31 17:54 ` [PATCH 4/6] exec/cpu-common: Do not restrict CPU to 32-bit memory access maximum Philippe Mathieu-Daudé
2020-05-31 19:41 ` Peter Maydell
2020-06-01 7:30 ` Philippe Mathieu-Daudé
2020-05-31 17:54 ` [PATCH 5/6] exec: Restrict 32-bit CPUs to 32-bit address space Philippe Mathieu-Daudé
2020-05-31 19:09 ` Peter Maydell
2020-06-01 8:09 ` Philippe Mathieu-Daudé
2020-06-01 10:45 ` Peter Maydell
2020-06-02 0:01 ` Richard Henderson [this message]
2020-05-31 17:54 ` [RFC PATCH 6/6] memory: Use CPU register size as default access_size_max Philippe Mathieu-Daudé
2020-05-31 19:14 ` Peter Maydell
2020-06-01 8:13 ` Philippe Mathieu-Daudé
2020-05-31 18:31 ` [PATCH 0/6] exec/memory: Rework some address and access size limits no-reply
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