On 6/6/20 7:15 PM, Ard Biesheuvel wrote: > Some instructions in the ARM ISA have multiple output registers, such > as ldrd/ldp (load pair), where two registers are loaded from memory, > but also ldr with indexing, where the memory base register is incremented > as well when the value is loaded to the destination register. > > MMIO emulation under KVM is based on using the architecturally defined > syndrome information that is provided when an exception is taken to the > hypervisor. This syndrome information describes whether the instruction > that triggered the exception is a load or a store, what the faulting > address was, and which register was the destination register. > > This syndrome information can only describe one destination register, and > when the trapping instruction is one with multiple outputs, KVM throws an > error like > > kvm [615929]: Data abort outside memslots with no valid syndrome info > > on the host and kills the QEMU process with the following error: > > U-Boot 2020.07-rc3-00208-g88bd5b179360-dirty (Jun 06 2020 - 11:59:22 +0200) > > DRAM: 1 GiB > Flash: error: kvm run failed Function not implemented > R00=00000001 R01=00000040 R02=7ee0ce20 R03=00000000 > R04=7ffd9eec R05=00000004 R06=7ffda3f8 R07=00000055 > R08=7ffd9eec R09=7ef0ded0 R10=7ee0ce20 R11=00000000 > R12=00000004 R13=7ee0cdf8 R14=00000000 R15=7ff72d08 > PSR=200001d3 --C- A svc32 > QEMU: Terminated > > This means that, in order to run U-Boot in QEMU under KVM, we need to > avoid such instructions when accessing emulated devices. For the flash > in particular, which is a hybrid between a ROM (backed by a memslot) > when in array mode, and an emulated MMIO device (when in write mode), > we need to take care to only use instructions that KVM can deal with > when they trap. > > So override the flash accessors that are used when running on QEMU. > Note that the write accessors are included for completeness, but the > read accessors are the ones that need this special care. > > Signed-off-by: Ard Biesheuvel <a...@kernel.org> > --- > board/emulation/qemu-arm/qemu-arm.c | 55 ++++++++++++++++++++ > include/configs/qemu-arm.h | 1 + > 2 files changed, 56 insertions(+) > > diff --git a/board/emulation/qemu-arm/qemu-arm.c > b/board/emulation/qemu-arm/qemu-arm.c > index 1b0d543b93c1..32e18fd8b985 100644 > --- a/board/emulation/qemu-arm/qemu-arm.c > +++ b/board/emulation/qemu-arm/qemu-arm.c > @@ -142,3 +142,58 @@ efi_status_t platform_get_rng_device(struct udevice > **dev) > return EFI_SUCCESS; > } > #endif /* CONFIG_EFI_RNG_PROTOCOL */ > + > +#ifdef CONFIG_ARM64 > +#define __W "w" > +#else > +#define __W > +#endif > + > +void flash_write8(u8 value, void *addr) > +{ > + asm("strb %" __W "1, %0" : "=m"(*(u8 *)addr) : "r"(value)); > +} > + > +void flash_write16(u16 value, void *addr) > +{ > + asm("strh %" __W "1, %0" : "=m"(*(u16 *)addr) : "r"(value)); > +} > + > +void flash_write32(u32 value, void *addr) > +{ > + asm("str %" __W "1, %0" : "=m"(*(u32 *)addr) : "r"(value)); > +} > + > +void flash_write64(u64 value, void *addr) > +{ > + BUG(); /* FLASH_CFI_64BIT is not implemented by QEMU */
Why should this BUG() on aarch64? Why is panicking in U-Boot better than crashing in QEMU? Why can't this be realized as two 32bit writes? This seems to be wrong: drivers/mtd/cfi_flash.c:179: /* No architectures currently implement __raw_readq() */ I find definitions for all architectures. So shouldn't you correct cfi_flash.c and override __arch_getq() and __arch_putq() instead? > +} > + > +u8 flash_read8(void *addr) > +{ > + u8 ret; > + > + asm("ldrb %" __W "0, %1" : "=r"(ret) : "m"(*(u8 *)addr)); > + return ret; > +} > + > +u16 flash_read16(void *addr) > +{ > + u16 ret; > + > + asm("ldrh %" __W "0, %1" : "=r"(ret) : "m"(*(u16 *)addr)); > + return ret; > +} > + > +u32 flash_read32(void *addr) > +{ > + u32 ret; > + > + asm("ldr %" __W "0, %1" : "=r"(ret) : "m"(*(u32 *)addr)); > + return ret; > +} > + > +u64 flash_read64(void *addr) > +{ > + BUG(); /* FLASH_CFI_64BIT is not implemented by QEMU */ Same here. Best regards Heinrich > +} > diff --git a/include/configs/qemu-arm.h b/include/configs/qemu-arm.h > index 1ef75a87836b..bc8b7c5c1238 100644 > --- a/include/configs/qemu-arm.h > +++ b/include/configs/qemu-arm.h > @@ -53,5 +53,6 @@ > #define CONFIG_SYS_MAX_FLASH_BANKS 2 > #endif > #define CONFIG_SYS_MAX_FLASH_SECT 256 /* Sector: 256K, Bank: 64M */ > +#define CONFIG_CFI_FLASH_USE_WEAK_ACCESSORS > > #endif /* __CONFIG_H */ >