[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2] xen/arm64: Remove vreg_emulate_sysreg32
Hi Julien, On 29.07.2021 13:20, Julien Grall wrote: > Hi Michal, > > On 29/07/2021 11:42, Michal Orzel wrote: >> According to ARMv8A architecture, AArch64 registers >> are 64bit wide even though in many cases the upper >> 32bit is reserved. Therefore there is no need for >> function vreg_emulate_sysreg32 on arm64. This means >> that we can have just one function vreg_emulate_sysreg >> using new function pointer: >> typedef bool (*vreg_reg_fn_t)(struct cpu_user_regs *regs, >> register_t *r, bool read); >> >> Modify vreg_emulate_cp32 to use the new function pointer >> as well. >> >> This change allows to properly use 64bit registers in AArch64 >> state and in case of AArch32 the upper 32 bits of AArch64 >> registers are inaccessible and are ignored(D1.20.1 ARM DDI 0487A.j). > > What you wrote only says that the bits are ignored. It doesn't say whether > the bits will be 0. > > They are probably, but as I wrote yesterday, I couldn't confirm it. > Should I then remove this part of the commit or write below?: "We can assume that those bits will be 0 but the architecture reference manual does not clarify this." >> >> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx> > > Please provide a change log. > Ok. > Cheers, > Cheers,
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