Re: [PATCH v2 5/9] nvram: add nrf51_soc flash read method

[P J P]

+-- On Tue, 21 Jul 2020, Philippe Mathieu-Daudé wrote --+
| On 7/21/20 8:47 AM, P J P wrote:
| > +-- On Thu, 16 Jul 2020, Peter Maydell wrote --+
| > | > The 'flash_ops' is for ROM, though I don't see where it calls 
| > | > 'memory_region_rom_device_set_romd' to ROMD, so this MR is in MMIO 
| > | > mode and it needs a read callback.
| > | 
| > | I think that 'romd mode' (ie reads-go-directly-to-RAM) is the default: 
| > | memory_region_initfn() sets romd_mode to true. So unless the device 
| > | actively calls memory_region_rom_device_set_romd(mr, false) then the 
| > | read callback can't be reached.
| > 
| > So, we go with g_assert_not_reached() ? We seem to have differing opinions 
| > about these callbacks.
| 
| - Callback missing because we neglected to implement the
|   hardware behavior:
| 
|   => qemu_log_mask(LOG_UNIMP, ...)
| 
| - Callback missing because the access is illegal on hardware
|   (write on read-only register, read on write-only register):
| 
|   => qemu_log_mask(LOG_GUEST_ERROR, ...)
| 
| - Impossible situation unrelated to the hardware/guest behavior
|   (problem in QEMU design)
| 
|   => g_assert_not_reached()
| 
| Note, when we runs QEMU with LOG_UNIMP/LOG_GUEST_ERROR enabled,
| we are usually interested in what address the guest is accessing,
| and in the write case, what value is written.

Okay, preparing a revised patch series.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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