Hi,
On 04.10.24 14:10, Peter Maydell wrote:
> On Fri, 4 Oct 2024 at 12:51, Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote:
>> On 04.10.24 12:40, Peter Maydell wrote:
>>> Don't do this -- KVM doesn't support it. For access to MMIO,
>>> stick to instructions which will set the ISV bit in ESR_EL1.
>>>
>>> That is:
>>>
>>> * AArch64 loads and stores of a single general-purpose register
>>> (including the register specified with 0b11111, including those
>>> with Acquire/Release semantics, but excluding Load Exclusive
>>> or Store Exclusive and excluding those with writeback).
>>> * AArch32 instructions where the instruction:
>>> - Is an LDR, LDA, LDRT, LDRSH, LDRSHT, LDRH, LDAH, LDRHT,
>>> LDRSB, LDRSBT, LDRB, LDAB, LDRBT, STR, STL, STRT, STRH,
>>> STLH, STRHT, STRB, STLB, or STRBT instruction.
>>> - Is not performing register writeback.
>>> - Is not using R15 as a source or destination register.
>>>
>>> Your instruction is doing writeback. Do the address update
>>> as a separate instruction.
With readl/writel implemented in assembly, I get beyond that point, but
now I get a data abort running an DC IVAC instruction on address 0x1000,
where the cfi-flash is located. This instruction is part of a routine
to remap the cfi-flash to start a page later, so the zero page can be
mapped faulting.
Simple reproducer:
start:
ldr x0, =0x1000
ldr x1, =0x1040
bl v8_inv_dcache_range
mov w10, '!'
bl putch
ret
v8_inv_dcache_range:
mrs x3, ctr_el0
lsr x3, x3, #16
and x3, x3, #0xf
mov x2, #0x4
lsl x2, x2, x3
sub x3, x2, #0x1
bic x0, x0, x3
1:
dc ivac, x0
add x0, x0, x2
cmp x0, x1
b.cc 1b
dsb sy
ret
This prints ! without KVM, but triggers a data abort before that with -enable-kvm:
DABT (current EL) exception (ESR 0x96000010) at 0x0000000000001000
elr: 000000007fbe0550 lr : 000000007fbe01ac
[snip]
Call trace:
[<7fbe0550>] (v8_inv_dcache_range+0x1c/0x34) from [<7fbe0218>] (arch_remap_range+0x64/0x70)
[<7fbe0218>] (arch_remap_range+0x64/0x70) from [<7fb8795c>] (of_platform_device_create+0x1e8/0x22c)
[<7fb8795c>] (of_platform_device_create+0x1e8/0x22c) from [<7fb87a04>] (of_platform_bus_create+0x64/0xbc)
[snip]
Any idea what this is about?
Thanks,
Ahmad
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